Sustainable management of leisure and professional fisheries at the ...

Sustainable management of leisure
and professional fisheries at the
level of the SILMAS partnership:
practices for managing resources, monitoring, and
conflict resolution

Acknowledgements
This technical guide was completed thanks to contributions
made by all of the European partners to the SILMAS project.
For their active involvement in providing data, validating the
various stages, and for final reading and validation of the
document (02/03/2012), the authors would like to thank the
following people in particular: Bernd WAHL (LUBW – Lake
Constance), Sébastien CACHERA (CISALB – Lake Bourget),
Clara BRAVI and Daniele MAGNI (Lombardy Region – Lake
Idro and Lake Iseo), Livio MALLIA (ERSAF – Lake Iseo),
Tina LESKOSEK and Anton BRANCELJ (NIB - Lake Bohinj),
Franck GLEIZE and Fanny DOU (SMADESEP – Lake Serre-
Ponçon), Roswitha FRESNER and Stéphanie KLAUS
(KIS – Lake Ossiach and Lake Wörthersee), Alberto MAFFIOTI
and Michela TONUSSI (ARPA Piedmont – Lake Avigliana and
Lake Candia), and Barbara ZENNARO and Maurizio SILIGARDI
(APPA Trento – Lakes Caldonazzo, Garda, Ledro, Levico, and
Terlago).
Co-ordination and implementation: Damien ZANELLA –
Syndicat Mixte du Lac d’Annecy - May 2012
Photos on page 1: © C. HAASE, R. MASSON, M. REIGNIER, D. ZANELLA / SILA.
Photos without mention of the author were provided by all partners of the SILMAS
project for use in reports and communication materials. Creating, printing: messaggio
Morning tranquillity on Lake Annecy (Photo: D. ZANELLA – SILA)
Syndicat Mixte du Lac d’Annecy - SILA
7, rue des Terrasses - 74960 CRAN-GEVRIER - FRANCE
www.sila.fr - Email: sila@sila.fr

Contents
I. About SILMAS.......................................................................................................... 6
1. The general framework: the Alpine Space Programme........................................... 7
2. SILMAS: some facts and figures.............................................................................. 7
II. Progress of the action dedicated to fishing management practices 8
1. Objectives................................................................................................................ 9
2. The methodology used.......................................................................................... 10
III. Presentation of interesting feedback within the
partnership – fisheries and knowledge management
actions...................................................................................................................... 11
1. Lake Constance (D-A-CH): co-ordination of fisheries activities at the level of a
major international lake.......................................................................................... 12
2. Lake Annecy (F): fishing management within a context of marked
oligotrophication of the lake and leisure and professional fisheries
exploitation, with whitefish as an example............................................................ 17
3. Lake Bourget (F): assessment of practices for restocking lacustrian Salmonidae... 25
4. Lake Idro (I): evaluation and adaptation of fishing management within
a context of conflict between the various categories of fishermen........................ 32
5. Lake Bohinj (SLO): regulation of fishing and other leisure activities within
a context of strong environmental preservation..................................................... 36
IV. Presentation of interesting feedback within the partnership –
habitat restoration actions............................................................................ 40
1. Lake Iseo (I): restoration of fish habitats by submerging physical structures........41
2. Lake Serre-Ponçon (F): project for the creation of experimental spawning
grounds within the context of an artificial Lake with major fluctuations in water
levels...................................................................................................................... 47
3. Lake Ossiach (A): creation of a huge wetlands zone on the lake’s edge,
providing spawning grounds.................................................................................. 56
V. The lessons from the experiments conducted within the
partnership, and transposing them.......................................................... 62
1. The importance of knowledge of the fish stocks................................................... 63
2. Taking into account the quality of the lake and its monitoring............................... 64
3. Monitoring fisheries activities and the evaluation of management practices......... 64
4. The implementation of habitats restoration actions............................................... 65
5. Local governance that is indispensable................................................................. 66
VI. Summary sheets relating to each lake..................................................... 67
5

© M. REGNIER / SILA
I. About SILMAS

1.
The general framework: the
Alpine Space Programme
The SILMAS project (www.silmas.eu) forms part
of the Alpine Space Programme, which in turn
is part of the European Community’s European
Territorial Cooperation programme. Category B
programmes relate to trans-European co-operation
and are aimed at encouraging harmonious,
balanced development of Europe’s territory. Under
this framework, the SILMAS project (Sustainable
Instruments for Lakes Management in the Alpine
Space) is developing transnational co-operation
between 5 countries in the Alpine arc: Germany,
Austria, France, Italy and Slovenia. Transnational
co-operation contributes to national cohesion
and reinforces the Alpine Space as an attractive,
powerful space for living and working in.
2.
SILMAS: some facts and figures
SILMAS
Leader
Sustainable Instruments for Lakes Management in the Alpine Space
It follows up on the ALPLAKES project (www.alpine-space.org/alplakes.html)
Rhône-Alpes Region (France)
Duration 3 years: September 2009 - August 2012
Budget
Objectives
Partnership
Organization
Total budget of €3,260,993, 76 % of which is financed by Europe (ERDF)
SILMAS is a project for pooling experience and know-how in terms of the sustainable
management of alpine lakes. Its goal is to produce concrete, sustainable tools
for better management of alpine lakes and in order to raise the general public’s
awareness of the sustainable development stakes involved in the lakes
5 countries are involved: Germany, Austria, France, Italy, and Slovenia
22 lakes; 15 partners from local bodies, environmental administrative authorities,
research institutes, and universities
3 working groups:
• Study of the effects of climate change on alpine lakes (WP4)
• Management of conflicts relating to the uses made of the lakes (WP5)
• Education regarding sustainable development concerning alpine lakes (WP6)
Lakes participating in the SILMAS project. Regions and Provinces that are partners to the project are shown in orange.
7

© R. MASSON
II. Progress of the
action dedicated
to fishing
management
practices

1. Objectives
Within the SILMAS project, the action relating to fisheries activities
forms part of the WP5 working group, which is dedicated to
governance and the management of conflicts which can arise due
to the various uses made of alpine lakes.
What is original about the SILMAS project is that
it brings together 5 countries to form a
partnership with a varied composition: local
bodies, environmental administrative bodies,
universities and research laboratories, etc. This
heterogeneousness makes it possible to compare
different points of view about the lakes and the
uses made of them, thus strengthening the quality
of the exchanges and understanding of the
expectations of the various actors.
Likewise, the lakes forming part of the network,
although they all belong to the same geographical
entity, show great diversity in terms of their
morphological characteristics. The largest one,
Lake Constance, which is flanked by Germany,
Austria and Switzerland, covers a surface area of
536 km², whereas the surface area of Lake Bohinj
in Slovenia “only” covers 3.3 km².
These basic factors in themselves constitute
important parameters for explaining the ecological
functioning of these water bodies, and particularly
the factors relating to ichthyofauna at the top of
the lacustrine food chain. Moreover, each lake is
subject to a context and to different anthropogenic
pressures. Inputs into the lake, via influents or
direct discharges (nutrients, organic materials, toxic
elements), are likely to have major consequences
on the internal functioning of the ecosystem, as
are physical changes to the habitats in the lake
or to its influents, management practices relating
to the lake, and the intentional or unintentional
introduction of non-indigenous species, etc.
Although the organizations and approaches differ
from country to country, region to region, and even
between lakes that lie only a few kilometres apart,
nevertheless, managers can be confronted by
similar issues.
This is where pooling experiences assumes
its full importance, and this constitutes this
working group’s second objective.
Several interesting actions have either been
implemented or are still under way at the various
lakes involved in the partnership, in fields as varied
as the restoration of spawning ground zones, the
management of fish resources between leisure
and professional fishermen, knowledge of stocks,
improving relations between fishermen and other
users of the lake, and so forth.
The SILMAS project thus provides an excellent
opportunity for highlighting, disseminating
and sharing these experiences throughout the
Alpine Space and beyond.
Even though this feedback is based on a specific
local context, the transfer of some or all of
these approaches that have been implemented
to other lakes can, it seems, be envisaged in
numerous cases.
Consequently, attempting a detailed comparison
of the water bodies would be quite meaningless
and would require the integration of a phenomenal
amount of data, bearing in mind moreover that
the level of knowledge, particularly concerning
the ichthyofauna, varies greatly from one site to
the next.
So the first objective of this action is primarily
to offer a general overview at the level of
the partnership, of the management of fish
resources and fisheries activities.
Work Package 5 (WP5) meeting
(Photo: Gw. P./SILA)
9

2. The methodology used
This action was co-ordinated by the Syndicat Mixte du Lac d’Annecy (SILA, www.sila.fr). All of
the project’s partners actively took part in gathering data, compiling feedback, and validating the
various stages.
A. GATHERING GENERAL DATA ABOUT THE LAKES
A questionnaire was disseminated within the
partnership during the first half of 2010, in order to
draw up a general inventory for each lake regarding
fishing and to provide a description of the fish
resources. The themes tackled related to general
information about fisheries exploitation, monitoring
fish populations and captures, management
practices, and any issues/conflicts and tools
implemented in order to resolve them.
More often than not, the project’s partners did
not have specific skills in the field of fishing
management, and had to pass on the questionnaire
to the local structures in charge of this theme. This
made it possible to obtain responses providing
varying levels of detail for 16 lakes:
- France: Lake Serre-Ponçon, Lake Annecy, and
Lake Bourget
- Germany/Austria/Switzerland: Lake Constance
- Austria: Lake Ossiach and Wörthersee
- Italy: Lakes Idro, Iseo, Candia, Avigliana Grande,
Caldonazzo, Ledro, Garda, Levico, and Terlago
- Slovenia: Lake Bohinj
For each lake, a sheet appended to the second
part of the technical guide presents the
information gathered, as well as the contact
details of the structure to be contacted in order
to obtain any further details.
B. PRESENTATION OF THE FEEDBACK
Subsequent to this initial exercise, several
particularly interesting experiments were
identified in the answers. For each of them, the
referent partners produced more comprehensive
presentations during the first half of 2011, as
provided in Chapters 3 and 4.
This feedback was organised into 2 main categories:
a. Fisheries and knowledge
management actions
- Lake Constance (D-A-CH): Co-ordination
of fisheries activities at the level of a major
international lake
- Lake Annecy (F): Fishing management within a
context of marked oligotrophisation of the lake
and professional and leisure fisheries exploitation,
with whitefish as an example
- Lake Bourget (F): Assessment of restocking
practices concerning lacustrian Salmonidae
- Lake Idro (I): Assessment and adaptation of
fishing management within a context involving
conflicts between the various categories of
fishermen
- Lake Bohinj (SLO): Regulation of fishing and
other leisure activities within a context of strong
environmental preservation
b. Actions for restoring fish habitats
- Lake Iseo (I): Restoration of fish habitats by
submerging physical structures
- Lake Serre-Ponçon (F): Project for the creation
of experimental spawning grounds within the
context of an artificial body of water with major
fluctuations in water levels
- Lake Ossiach (A): Creation of a huge wetlands
zone on the lake’s edge, providing spawning
grounds
Although each situation has its own particular
context, practical lessons can nevertheless be
drawn from these situations, which can then be
transposed to other lakes. Consequently, crossanalysis
of these eight case studies is provided
below (Chapter 5).

III. Presentation of
interesting
feedback within
the partnership –
fisheries and
knowledge
management actions
© Gw. P / SILA
11

1. LAKE CONSTANCE (D-A-CH):
Co-ordination of fisheries activities at the level of
a major international lake
LAKE CONSTANCE (D-A-CH)
Context
Tools
implemented
SILMAS
contact
• An international lake bordered by three States
• It experienced a period of eutrophication, and then a recent return to oligotrophic
status
• A high level of exploitation by professional and leisure fishermen
• Formalised international co-ordination since 1893
• Management based on good knowledge of the stocks and exploitation
LUBW - Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg
poststelle@lubw.bwl.de
A. PRESENTATION OF THE LAKE
Lake Constance is a peri-alpine lake of glacial
origin, consisting of 2 distinct basins (a lower
lake and an upper lake). It has a surface area of
535 km², and is shared by Austria, Germany and
Switzerland. Most of the water inputs are from the
alpine zone, which causes a high level in summer
as the result of melted snow, and a low level in
winter. The lake is used as a source of drinking
water for over 4 million inhabitants, and constitutes
a major attraction for tourist activities.
B. FISH POPULATION (ECKMANN & RÖSCH, 1998)
In total, 31 species populate Lake Constance,
which constitutes fairly much the same level of
diversity as at the start of the 20th century, although
major changes have occurred since then.
SPECIES BEFORE 1900 PRESENT DAY
Eel Anguilla anguilla X X
Lake trout Salmo trutta X X
Rainbow trout Oncorhynchus mykiss X
Arctic char Salvelinus alpinus X X

SPECIES BEFORE 1900 PRESENT DAY
Whitefish Coregonus lavaretus X X
Grayling Thymallus thymallus X X
Pike Esox lucuis X X
Roach Rutilus rutilus X X
Belica Leucaspius delineatus X X
Common dace Leuciscus leuciscus X X
Chub Leuciscus cephalus X X
Minnow Phoxinus phoxinus X X
Rudd Scardinius erythrophthalmus X X
Tench Tinca tinca X X
Common nase Chondrostoma nasus X X
Gudgeon Gobio gobio X X
Barbel Barbus barbus X X
Bleak Alburnus alburnus X X
Silver bream Blicca bjoerkna X X
Common bream Abramis brama X X
Bitterling Rhodeus sericeus amarus X
Crucian carp Carassius carassius X X
Carp Cyprinus carpio X X
Stone loach Barbatula barbatula X X
European catfish Siluris glanis X X
Pumpkinseed Lepomis gibbosus X
Perch Perca fluviatilis X X
Pikeperch Stizostedion lucioperca X X
Ruffe Gymnocephalus cernuus X
Bullhead Cottus gobio X X
Three-spined
stickleback
Gasterosteus aculeatus
X
Burbot Lota lota X X
In the early 20th century, 4 forms of whitefish
(Coregonus sp.) occupied upper Lake Constance,
whereas there are now only 3 forms, although in large
numbers: a type of whitefish that utilises pelagic
reproduction (its local name is “Blaufelchen”),
and forms which reproduces in the littoral zone
(the “Gangfisch” and the “Sandfelchen”).
The bleak (Alburnus alburnus), which was the
most abundant species in the 19th century, nearly
disappeared in the 1980s; the population does
however seem to have re-established itself in the
last few years.
The new species are the three-spined stickleback
(Gasterosteus aculeatus), the rainbow trout
(Oncorhynchus mykiss), the pumpkinseed
(Lepomis gibbosus) and, more recently, the ruffe
(Gymnocephalus cernuus), which was discovered
for the first time in 1987. It is not known where it
was introduced from, and its numbers have been
steadily increasing since 1992, to the extent that it
is currently becoming the most abundant species
in the shallow zone. The ruffe mainly feeds on
benthic prey, apart from during winter, when
whitefish eggs constitute the bulk of its diet, to
the extent that it can have an influence on the
successful reproduction of this form of whitefish.
13

We still do not know what the consequences of
the fish population of the recent introduction of
a non-indigenous species of freshwater shrimp
(Limnomysis benedeni) will be. It was discovered in
2006, and has subsequently been found throughout
the lake in large numbers. The initial tests carried
out seem to show that this crustacean is only
accepted as prey by the juveniles of perch.
C. CHARACTERISTICS OF FISHERIES EXPLOITATION
(ECKMANN & RÖSCH, 1998; RÖSCH, PERSONAL COMMUNICATION;
ZINTZ ET AL., 2009; WWW.IBKF.ORG)
There is a long tradition of professional fishing on
Lake Constance; in the early 20th century there
were over 400 professionals operating on the lake.
The fishing statistics are based on the annual
reports of the IBKF; the international commission
for the fishing management of Lake Constance.
The fishing yields do not necessarily reflect
the biomass and the composition of the lake’s
populations, because only a few species of
commercial interest are actively exploited: whitefish
and perch and, to a lesser extent, eel, lake trout,
pike, and pikeperch. The other species such as
Cyprinidae (roach, bream, common dace, etc.) only
constitute ancillary catches.
Professional fishing statistics have been available
since 1909. Commercial exploitation can be
divided into 3 periods:
- 1909 to 1955, with the average results being
around 415 tonnes per year, with a maximum of
approximately 700 tonnes;
- In 1956, for the first time, catches exceeded
1,000 tonnes, and up until the late 1990s, they
never fell below 750 tonnes, with an average of
about 1,104 tonnes per year;
- Since the late 1990s, catches have dropped
sharply to around 600 to 800 tonnes per year.
Fishing statistics for Lake
Constance in tonnes caught per year
(Source: www.ibkf.org)
(Barsch = Perch;
Felchen = Whitefish;
Sonstige = other species)
For whitefish, the yields vary from 150 to 1,200
tonnes. A constant characteristic is the major
variability from one year to the next without any
obvious periodicity. The changes that occurred
immediately after 1956 were partly due to an
improvement in the efficiency of the nets due
to the use of nylon. Traditionally, whitefish nets
were made from cotton: back then, the Catches
Per Unit-Effort (CPUE) were much lower with this
material than with nylon. Before 1955, commercial
catches mainly consisted of whitefish, with the
other species constituting less than 30 % of the
catches. Due to the eutrophication of the lake, the
whitefish proportion then dropped sharply to the
extent that it amounted to less than 40% of the
total catch in some years. The stocks exploited
today are characterised by a return to the situation
that existed before the period of eutrophication,
as whitefish constitutes 75 to 80 % of the catches.
However, the quantities of all species caught are
steadily decreasing, as is the average size of the
catches. The quality found in the lake, with its
oligotrophic status, is the main reason for this.
One positive effect of this reoligotrophication that
relates to the Arctic char should be emphasised,
as the current yield is almost 12 tonnes per
year as opposed to a hundred or so kg in the
early 1990s. The real impacts of restocking are
however unknown.

For the Cyprinidae, mainly roaches and breams,
the maximum yields in the 1970s do not reflect the
changing dynamics of the populations, as during
this period, these species were subsidised, which
made this fishing profitable. In 1981, financial
support was discontinued, and the catches
immediately fell to a much lower level.
Prior to 1950, perch was considered to be
an undesirable species. From the time when
professionals processed and presented the
product as fillets, the market value of perch
increased considerably, as did exploitation of it.
The period of eutrophication experienced by Lake
Constance enabled a major increase in perch
catches, partly due to an acceleration of its growth.
The interannual fluctuations do however remain
high, more often than not over 3-year cycles.
Currently, the lake is fished by over 13,000 amateur
fishermen and approximately 150 professional
fishermen. The numbers of the latter have been
decreasing for around ten years now, with the
economic situation being increasingly difficult
due to the decline in catches. It seems that the
fishermen who are doing the best out of this
situation are the ones who have adopted selling
their catches directly to consumers.
D. THE Organization OF FISHERIES ACTIVITIES
(LÖFFLER H., 1990; WWW.IBKF.ORG)
Since Medieval times, laws and regulations have
been in force and have set the framework for
fishing practices on Lake Constance.
The “Bregenz” agreement (Source: www.ibkf.org)
On 5 July 1893, the “Bregenz” agreement was
signed by all the governments with territory adjoining
the lake, including the Principality of Liechtenstein
which, although it does not hold that status, is
directly involved due to the presence on its territory
of lake influents which are fertile spawning grounds
for trout. To this day, this agreement constitutes the
oldest international treaty still in force relating to
the Organization of fishing which, in the case at
hand, applies to the upper part of Lake Constance.
Already based on the principle of sustainable
exploitation, this text defines the sectors where
activities can be carried out, the legal catch sizes,
the fishing periods for the various species, and
measures aimed at protecting the reproduction
of whitefish and lake trout. It is specified that the
introduction of new species is prohibited unless
prior information and authorisation is provided.
Details are provided of the Organization
of international governance by appointing
representatives of each government.
These days, the international commission for the
fishing management of Lake Constance (IBKF -
Internationale Bevollmächtigtenkonferenz für die
Bodenseefischerei, www.ibkf.org) consists of
Germany via the Länder of Baden-Württemberg and
Baveria, Austria via the Federal State of Vorarlberg,
Switzerland via the Cantons of Saint Gall and
Thurgau, and the Principality of Liechtenstein. The
chairmanship is on a rotating basis and involves
3-year terms of office. The initial agreement
concluded in 1893 is nowadays supplemented by
permanent directives, by the regulation applicable
to leisure fishing and professional fishing, and by
piscicultural management procedures.
The representatives are responsible for all of the
orientations adopted in terms of management. The
decisions must be made unanimously so that they
can then be transposed into national regulations
and thereby be applied by the 150 professional
fishermen and the 13,000 amateur fishermen on
the lake.
The international commission meets annually
for a plenary session in June. Each member
is responsible for drawing up an annual report
presenting the situation in its territory: the quantities
caught, interannual trends, the number of licences
issued, the quantities produced by fish farming, etc.
Moreover, the members appoint fishing experts,
15

scientists and administrative bodies that are
responsible for advising the commission. The
council of experts also meets at least once a year for
exchanges both concerning fishing management
issues and scientific issues, in order to prepare its
report and submit its proposals to the commission.
Specific working groups can also be established
in order to deal with specific points (for example,
migrating fish).
The international commission’s meetings
are relatively formal, and only government
representatives can take part in them, along with
a few guest experts, and the representatives
of amateur and professional fishermen (the
International Association of Fishing on Lake
Constance). The commission is however preceded
by preparatory meetings that bring together a
wider range of users.
E. SOME OF THE MANAGEMENT PRACTICES USED
(ZINTZ ET AL., 2009)
Various techniques have been put into practice
at Lake Constance and this is still the case today.
The whitefish population is supported by the
large-scale fish farming: numerous hatcheries are
located on the lakeside, where eggs are artificially
fertilised. To do this, the spawners are caught
from the lake in early December. The hatching of
the eggs and the growth of the larvae occur in an
artificial environment, with this providing higher
success rates than the bottom of the lake.
Fish restocking programmes have also been drawn
up for lake trout, at the same time as improving
migration conditions on influents so that spawning
grounds can be reached (the construction of
fish-passes).
Moreover, there is a very old tradition at Lake
Constance which dates back to the 17th century,
which involves submerging piles of branches and
brushwood that are used for spawning grounds
and nurseries for numerous species. Over the
last few decades, these practices have gradually
fallen into disuse. However, experiments are
being conducted involving new solutions that are
more sustainable over time, particularly with the
help of metal structures filled with branches and
brushwood. The initial results seem very positive.
F. SUMMARY WRITTEN BASED ON THE FOLLOWING REFERENCES
ECKMANN R., RÖSCH R., 1998. Lake Constance
fisheries and fish ecology. Arch. Hydrobiol. Adv.
Limnol. 53, 285-301.
LÖFFLER H., 1990. Fisheries management of
Lake Constance: an example of international cooperation.
In: W.L.T. van Densen, B. Steinmetz &
R.H. Hughes (Eds.). Management of freshwater
fisheries. Proceedings of a symposium organized
by the European Inland Fisheries Advisory
Commission, Göteborg, Sweden, 31 May-3 June
1988. Pudoc Wageningen: 38-52.
ZINTZ K., LÖFFLER H., SCHRÖDER H.G., 2009.
Lake Constance - A natural environment in change.
Web site: www.ibkf.org

2. LAke ANNECY (f):
Fishing management within a context of marked
oligotrophication of the lake and leisure and
professional fisheries exploitation, with whitefish
as an example
View of Lake Annecy from the highest point in its catchment area; La Tournette Massif (altitude 2,351 m)
(Photo: D. ZANELLA/SILA)
LAKE ANNECY (F)
Context
Tools
implemented
Author -
silmas
contact
• Marked oligotrophication of the lake
• Regular declines in catches for leisure and professionals fishermen
• Recurring conflicts between leisure and professionals fishermen
• Assessment calling on scientists who are “external” to the lake’s management
• Acquisition of recent scientific data on exploitation of the various species
• Consultation between the various actors and development of regulations
Syndicat Mixte du Lac d’Annecy – SILA
sila@sila.fr ; www.sila.fr
A. A BRIEF DESCRIPTION OF THE LAKE
With a surface area of 27 km², Lake Annecy is the
second largest natural body of water in France,
and it is located at an altitude of 447 m. It is of
glacial origin, with an average depth of 41 m, and
its maximum depth is 65 m at the centre of the
centre of the lake’s basin.
Like numerous other European water bodies,
Lake Annecy experienced an eutrophication
phase mainly due to domestic inputs: the lack
of a sewage system, direct discharges into the
lake, and an increase in the lakeside population.
The initial consequences for the ecosystem were
reported in the late 1940s. The warning sounded
by scientists and the commitment made by several
elected officials towards preserving the lake
enabled a mobilisation of lakeside boroughs, with
the creation of an interborough structure; the SILA
(www.sila.fr).
From 1962 onwards, this body committed itself
to the construction of a huge sewage network
ringing the lake, which enabled the collection of all
the wastewater from the catchment area. It is routed
to a pollution treatment plant where it is treated,
and is then returned to the natural environment but
not to the lake, with this occurring downstream in
the Fier River, the catchment area’s final outlet.
The nutrients enrichment period was thus limited:
the phosphorus concentration never exceeded
20 µg Ptot/l; nowadays it is stabilised at around
5 µg Ptot/l. The lake is considered to be oligotrophic,
its biological compartments are well balanced,
and quality monitoring of the ecosystem has been
implemented every year since 1966 (http://www.
sila.fr/inter.php?rubrique=119).
17

B. THE FISH POPULATION OF LAKE ANNECY
Recent pelagic and littoral sampling operations
(ONEMA 2007, 2010) have made it possible to
update the inventory of species. The common
bream (Abramis brama) and the carp (Cyprinus
carpio), which were not sampled but are indeed to
be found in the lake, were added to this list, which
features 19 species.
SPECIES LATIN name SPECIES LATIN name
Lake trout Salmo trutta Bleak Alburnus alburnus
Arctic char Salvelinus alpinus Silver bream Blicca bjoerkna
Whitefish Coregonus lavaretus Common bream Abramis brama
Pike Esox lucuis Carp Cyprinus carpio
Roach Rutilus rutilus Stone loach Barbatula barbatula
Common dace Leuciscus leuciscus Perch Perca fluviatilis
Chub Leuciscus cephalus Bullhead Cottus gobio
Rudd Scardinius erythrophthalmus Burbot Lota lota
Tench Tinca tinca Blennie Salaria fluviatilis
Gudgeon
Gobio gobio
The lake also hosts a population of spiny-cheek
crayfish (Orconectes limosus) and a population of
signal crayfish (Pacifastacus leniusculus), both of
which were introduced.
Several earlier studies (1860, 1908, 1928, cited
in Gerdeaux, 1995) revealed the presence of
other species, some of which were abundant,
but which have not been found since, such as
the eel (Anguilla anguilla), the minnow (Phoxinus
phoxinus), the vairone (Telestes soufia), and the
rainbow trout (Oncorhynchus mykiss). In 1999,
divers filmed the presence of a significantly large
European catfish (Siluris glanis). The absence
of any reports since, either during dives or
concerning fishermen’s catches, suggest that
this “clandestine” introduction of one or more
individuals did not enable this species to become
self-supporting.
The lake’s two symbolic species which are the
most sought after these days, the whitefish and the
Lake Annecy Arctic char
(Photo: J-L. BERTONCELLO)
Arctic char, were introduced for the first time in 1888
and 1890 respectively. Young fish continued to be
placed in the lake throughout the first half of the
20th century, with these operations involving fish
of very diverse origins (Lake Constance, Geneva,
Bourget, Neuchâtel, Scandinavian countries, etc.).
C. THE Organization OF THE FISHERY OF LAKE ANNECY
a. Regulation and governance
The lake is owned by the French State, which
also holds the fishing rights. Fishery exploitation
involves renting a fishing lease from the leisure
fishermen’s association, and the issuing of a
fixed number of professional fishing licences.
The principle adopted for defining management
and regulations, which was reaffirmed in 2010, is
equitable, sustainable sharing of the fish resource
by the two categories of fishermen.
In France, only professional fishermen have the
right to sell their catches. In the case of Lake
Annecy, the supply is much smaller than the
demand, which means that outlets are solely local:
mainly restaurant owners, along with some direct

selling to private individuals, and sometimes to
fishmongers and supermarkets.
lines of business being very frequent up until that
time (working in the restaurant trade, farming,
etc.). From the late 1990s to 2010, 4 professional
fishermen operated over the whole lake.
Over the last decade, the number of amateur
fishermen in boats has stabilised at around 1,000
licences issued annually, after having experienced
a peak of nearly 1,400 licence-holders in 2001.
A professional fisherman returns to the jetty
(Photo: D. ZANELLA/SILA)
The lake’s fishing regulation, which complies with
national fishing legislation, is supplemented by a
specific annual Order which specifies certain points
in the regulations. This Order is issued by the local
representative of the State - the Prefect - based on
the opinion of a Fishing Consultative Commission.
This Consultative Commission is a body that
provides information, conducts exchanges,
and holds consultations which bring together
individual representatives of each of the actors
involved in fishing management: leisure fishermen,
professional fishermen, local bodies, environmental
administrative authorities, fisheries experts,
and environmental protection associations. The
Commission meets at the end of the year in order
to take stock of the past season and to debate any
modifications to be made to the regulations, fishing
management, and so forth.
Fishing for whitefish and Arctic char on Lake Annecy using
a “sonde”, a line with a lead weight on the end fitted with
lures that look like Chironomidae larvae and nymphs
(Photo: D. ZANELLA/SILA)
b. Practices relating to fishing
management and knowledge
about exploitation
Lake Annecy has not been stocked with whitefish
fry since 1997, with all additional stocks now
being the result of natural reproduction.
Number of leisure fishermen
Number of professional fishermen
Reproduction of whitefish in the lake’s littoral zone in late
December/early January (Photo: D. ZANELLA/SILA)
The Arctic char population is sustained every
year by the introduction of approximately 100,000
juveniles at different points around the lake.
The number of leisure fishermen in boats and professional
fishermen on Lake Annecy (Source: DDT)
The spectacular drop in the number of professional
fishermen after 1971 is due to a change in the
regulations, which required professionals to have
fishing as their only source of income, with multiple
Both professional fishermen and amateur
fishermen in boats are required to fill in
“obligatory” statistics in a catch book, and to
forward them to the State service in charge of
fishing (the Departmental Office of Territories,
“DDT” in French). Additional, more detailed data
are also provided by twenty or so volunteer leisure
19

fishermen, with the data being analysed by INRA
(National Institute for Agronomic Research) from
1987 to 2007, and since then it has been analysed
by the leisure fishermen’s association (“Annecy
Lac Pêche”).
D. RECENT DEVELOPMENT OF FISHING AT THE LAKE, WITH REFERENCE TO THE
SPECIAL CASE OF WHITEFISH
A survey conducted in relation to the leisure
fishermen operating on the shores of Lake Annecy
(Fédération de Pêche de Haute-Savoie (Haute-
Savoie Fishing Federation), 2009) shows that the
impact of these catches seems to be very limited
compared to fishing from boats (by both leisure
and professional fishermen). The species sought
after by shore fishermen are perch (juveniles and
adults), followed by pike, whitefish, Arctic char and
lastly Cyprinidae. This study’s estimate was that
455 whitefish were caught from the lake’s shores
during the 2009 fishing season, amounting to
260 kg (the average weight of a whitefish caught
from a boat in 2009 was 0.570 kg). At the same
time, amateur fishermen in boats caught over
7 tonnes.
Catches of lake trout are at a much lower level,
but have been fairly stable over the years: 300 to
600 kg for amateur fishermen and 100 to 200 kg for
professionals.
In the case of whitefish, although fluctuations have
been observed over the timespan considered, the
trend is towards an overall decline in catches. This
began in 2004-2005 in the case of amateurs, and
from 2007 onwards in the case of professionals.
Consequently, the following pages of the document
will be devoted solely to the practice of fishing
Salmonidae from boats (whether operated by
amateurs or professionals), with a special focus on
the case of whitefish.
Whitefish: catches in kg (Source: DDT)
Arctic char: catches in kg (Source: DDT)
Concerning Arctic char, for the professionals
fishermen, the results are a few hundred kg or so
every year. For leisure fishermen, catches have
continually declined over the last decade: 2,000
to 3,000 kg were caught over the last few years,
whereas catches were over twice that level in the
late 1990s. The case of Arctic char is not developed
in this presentation, but it has formed the subject
of investigations in an endeavour to understand
the reasons for this decline. However to date, no
specific explanation has been found.
As whitefish is the most sought-after species in
Lake Annecy, this situation rapidly reinforced a
climate that had already been conflictual in the
past. The representatives of leisure fishermen
reproached the four professionals for exerting too
great a pressure in terms of fishing, and of being
continually favoured by the State via its regulations.
At the same time, the low catches by professional
fishermen no longer enabled them to ensure they
received a minimum income which, in the short
term, threatened the economic viability of their line
of work.
Within this context, the State and SILA implemented
a series of actions in order to understand the
reasons for this decline in catches, to change
management practices if necessary, and to thereby
improve the situation.
a. 2007: The initial fishing assessment
In order to obtain a “new”, independent view
of Lake Annecy’s situation, the State and SILA
organised a fishing assessment by three foreign
specialists, whose names were validated by all the
stakeholders. As preparation for the exercise, all of
the available data relating to fishing management

and quality monitoring of the lake were forwarded
to the experts beforehand.
As a supplement to this, scientific sampling using
nets was carried out by ONEMA (the National
Water and Aquatic Environments Office) in early
October 2007, in accordance with European
standard EN 14757.
by leisure and professional fishermen (for 1996
to 2005).
The whitefish population is functional, and gives
rise to cohorts that can be exploited even though
their size varies from one year to the next: the
quantity of spawners and reproductive success,
the climate, diet, predation, etc. A return to stocking
the lake with fry is not justified.
Yield
“Unmeshing” the scientific nets and sorting the species
caught in them (Photo: D. ZANELLA/SILA)
The experts then spent 3 days in Annecy in
November 2007, in order to conduct exchanges
with all of the actors involved at group and individual
meetings. Their conclusions formed the subject of
a report forwarded in December 2007.
This initial analysis showed that the lake does seem
to be relatively productive given its trophic status,
compared to other Swiss lakes for which data are
also available. Therefore it cannot be a matter of
increasing the total yield, but rather of retaining an
acceptable yield in terms of Salmonidae and to
achieve a suitable allocation of catches between
leisure fishing and professional fishing.
The relationship between the annual fishing yield and the
trophic levels of five Swiss lakes and Lake Annecy
(Source: MULLER R., PATTAY D., ROESCH R., 2007)
The available data have not enabled the experts to
explain the decline in catches in relation to leisure
fishing from 2004 to 2006, while the yield enjoyed
by the professional fishing sector was still stable
during this period. Changes in the dietary habits
or movements of the whitefish, as well as fishing
sessions slightly more targeted towards Arctic char
were mentioned.
With the fishing statistics as the only available
data, supplemented by a single recent sampling
operation (ONEMA, October 2007), the experts
were unable to draw conclusions about the state
and dynamics of the Salmonidae populations. The
absence of certain important recent data, such
as the age of the fishes caught, whitefish growth
and sexual maturity, meant that they were unable
to draw up a full inventory. The experts therefore
recommended that this information be acquired as
soon as possible
b. 2008 to 2010: Establishment of a
Fisheries Scientific Committee and
the acquisition of supplementary
data
In order to advise the Consultative Commission
for Fishing on Lake Annecy and to be a source of
proposals in terms of studies and management, the
Prefect created a Fisheries Scientific Committee
in June 2008, which consists of 9 members from
various structures. The Chairman of this Committee
also takes part in the Consultative Commission
in order to present the positions of scientists
concerning the topics dealt with.
Pursuant to the assessment’s recommendations,
the DDT and SILA ordered and financed the
completion of fishing monitoring over 3 seasons
(2008 to 2010) in order to obtain the missing data
referred to in 2007. These data were acquired and
analysed by INRA. The specifications for each year
of study, as well as the report presenting the results
obtained, were subject each time to the Fisheries
Scientific Committee for validation.
The yields for the five Swiss lakes include all of the
fish caught by professional fishermen, while those
for Lake Annecy include only Salmonidae caught
Over these 3 years, the basis of the study
consisted of monitoring the whitefish size and age
structure in the catches of one of the 4 professional
fishermen by measuring, weighing and sampling a
21

atch of scales from at least 100 individuals every
month. This sampling effort, which was particularly
comprehensive, could only be carried out with
the voluntary, diligent collaboration of the
professional fisherman.
Different pieces of knowledge were also monitored
over one or more of these years:
- The diet of the whitefish, by analysing the contents
of at least 20 stomachs per month in 2008 and
2009 and, on a more one-off basis, the diet of the
pikes, Arctic chars, roaches, perches and burbots
caught by the professional fisherman;
- The sex and level of maturity of all sizes of
whitefish, sampled thanks to scientific sampling
using nets with different mesh sizes, in September
2008 and July 2009;
- The growth of pikes (2008) and perches (2009),
based on scales and otoliths.
At the same time, other studies were also
conducted over this period. The ONEMA carried
out a sampling operation using electric fishing
in the lake’s littoral area, and in October 2010
repeated a scientific fishing sampling using nets
compliant with European standard EN 14757.
The monthly diet of whitefish in Lake Annecy in 2008
and 2009 split into fishes caught in the pelagic zone
and in the benthic zone (Source: GERDEAUX, 2010)
The existence of a substantial stock of scales
archived at the INRA station at Thonon-les-Bains
enabled a history of the growth of whitefish in
Lake Annecy to be drawn up. It is clear from this
that there has been a downward growth trend for
sizes at the ages of 2 and 3 years, even though
a shift has been observed for individuals born in
2005 and 2006. The overall trend may be related
to the oligotrophication of the lake. The resumption
of growth for those individuals born more recently
seems to be correlated with a great abundance in
2005 and 2006 of the zooplankton taxons, which
are the preferred food consumed by the whitefish
(Leptodora, Bytotrephes and Daphnia genuses).
Consequently, there was major progress in
terms of knowledge about the fish population of
Lake Annecy thanks to these 3 years’ worth of
investigations. Unfortunately, it is not possible to
make reference to all of the results obtained in this
document, and only the main conclusions relating
to whitefish are briefly presented.
In relation to the diet of the whitefish, the 2008
and 2009 results were relatively close, and
clearly demonstrated that the distribution of prey
greatly depends on the habitat frequented by
the individuals. Thus, the whitefish caught in the
pelagic zone (using a pelagic net) preferred to
feed on zooplankton, while the individuals caught
near the bottom and in the more littoral zone
(using a “spider” net) basically consumed benthic
invertebrates: Chironomidae nymphs and larvae,
and molluscs.
Total length back-calculated at 1 (“L1”), 2 (“L2”) and
3 years (“L3”) for Lake Annecy whitefish depending
on the year of birth of the fishes (abscissas axis).
(Source: GERDEAUX, 2010)
The shape of the distribution histograms according
to the length of the whitefish caught by the
professional fisherman changed over the 3 years
monitored. The mode increased in 2008 from
spring to summer; to the contrary it still remained
centred on 42 cm in 2009, then 39 cm in 2010.
Although you could distinguish the arrival of a
new generation at the end of the 2008 and 2009
seasons (with a peak of 39-40 cm), it is impossible
to distinguish any change in the distribution of the
sizes in 2010.

Lastly, observation of the whitefish captured by
the professional fisherman demonstrated that a
significant number of fish (14% in 2008 and 12% in
2009) showed major injuries on their lips, probably
indicative of a previous encounter with a fish hook:
whitefish caught by a fisherman and thrown back
in the water, or which were either not caught or not
hooked properly.
All of these observations made it possible to
demonstrate that Lake Annecy’s whitefish are
subject to strong pressure from fishermen as
a whole (both amateurs and professionals), the
consequences of which seem to have become
more marked over the last few years. The
population may be considered to be heavily
fished whenever the individuals reach the
minimum catch size of 38 cm.
Percentage distribution values for the lengths of whitefish
caught by professional fishermen from 2008 to 2010
(Source: Gerdeaux, 2011)
Concerning the age distribution, the majority of the
whitefish caught at the start of the season were
in the 5th year of their life (“4+”), as well as a few
“5+”, “6+” individuals and a very low proportion
of “3+” individuals. The “4+” generation remained
dominant from May to July, but the proportion of
“3+” individuals increased regularly, until it became
dominant at the end of the season. From 2008 to
2010, regardless of the period considered, fishing
simultaneously relied on 3 generations.
The average weight of whitefish in professional
fishing, which was quite stable from 2003 to
2006, changed substantially from 2008 onwards.
Unfortunately, the data for leisure fishing are
not available.
At the same time, from 2008 to 2010, amateur
fishermen reported an ever-increasing proportion
of small whitefish in their catches: over 8 fishes
out of 10 caught failed to match the legal size
and had to be returned to the water.
c. 2010 and 2011: The second fishing
assessment and amendments to
the regulations
During 2010, the State and the representatives of
local bodies in the catchment area reaffirmed their
determination to maintain professional fishing on
Lake Annecy, with fisheries management based on
equitable, sustainable sharing of the resource by
leisure and professional fishermen.
The 2007 fishing assessment was repeated in
November 2010, by entrusting the same three
experts with newly-acquired data. In the period
between these two assessments, the annual yield
in terms of Salmonidae (for both amateur and
professional fishermen) continued to decline, from
8.8 kg/ha in 2005 to less than 5 kg/ha in 2010.
This second stage of the assessment confirmed
certain points made in 2007 (the functionality
of the whitefish cycle, with there being no
justification for a return to stocking the lake with
young fish), and thanks to the data acquired, it
also raised the need to reduce the overall fishing
pressure on Salmonidae, from both professional
and leisure fishermen.
Average monthly weight in grams of whitefish in the
professional fishing (in red) and in the leisure fishing (in blue)
since 2003.
(Source: GERDEAUX, 2011)
Although a full review of the regulations did not
seem necessary, the experts nonetheless proposed
some modifications:
- Based on the accounts statement of a professional
fisherman and the current catch levels, maintaining
an acceptable income cannot be ensured for the
4 professional licence-holders. Also, the experts
23

ecommended gradually reducing the number
of professionals to 2, without for the time being
assigning either any additional fishing resources
to the latter, or catch quotas;
- In order to adapt to the reduced growth of whitefish,
the experts proposed reducing the mesh size of
pelagic nets from 54 mm to 50 mm, and for both
professionals and amateurs, lowering the legal
catch size from 38 cm to 36 cm. This measure
also has the objective of reducing incidental
mortality, which is unknown, but which is probably
substantial, being linked to the catching and then
the return to the water of whitefish specimens
that do not reach the legal size. This proposal is
associated with a reduction in the annual and daily
quotas for leisure fishermen, which would change
from 250 to 100 whitefish per year and from 8 to
4 whitefish per day;
- Perch is a species that currently is not exploited
at Lake Annecy. And yet in certain years its total
numbers are high, it may compete with whitefish,
and have an influence on its population. The
experts therefore proposed encouraging its
exploitation by the fishing sector which, moreover,
would reduce the pressure exerted on Salmonidae.
For example, the reduction in the mesh size of
certain nets by professional fishermen would
enable better catches of small young-of-the-year
perch (“0+”), the exploitation of which constitutes
a major source of income in other alpine lakes;
debated the various proposals made. Most of
them were adopted, and came into practice from
the 2011 fishing season onwards, with gradual
implementation in the case of some of them:
- 3 professional fishermen in 2011, and then
2 in 2012;
- The legal catch size for whitefish was lowered
to 37 cm in 2011;
- A gradual reduction over 2011 and 2012
of the annual and daily quotas for leisure
fishermen, in order to achieve the experts’
recommendations (100 whitefish per year and
4 whitefish per day).
E. REFERENCES CITED
Fédération de pêche de Haute-Savoie, 2009.
Première évaluation des captures de poissons par
pêche à la ligne depuis le bord du lac d’Annecy,
saison 2009. A study carried out at the request
of the Annecy Lac Pêche association and the
Département Directorate of the Territories of
Haute-Savoie.
GERDEAUX D., 1995. Le peuplement pisciaire du
lac d’Annecy. Bulletin No. 3 de la Société d’Histoires
Naturelles de la Haute-Savoie.
GERDEAUX D., 2009, 2010 and 2011. Suivi de la
pêche professionnelle au Lac d’Annecy. Rapports
annuels pour les saisons 2008, 2009 et 2010. SILA-
DDT-INRA agreement.
MÜLLER R., PATTAY D., ROESCH R., 2007 and
2010. Expertise halieutique du lac d’Annecy,
effectuée à la demande du SILA et de la DDT.
ONEMA, 2007 and 2010. Échantillonnage 2007 et
2010 du peuplement piscicole du lac d’Annecy.
Application du protocole EN 14757.
ONEMA, 2010. Échantillonnage de la faune pisciaire
de la zone littorale du lac d’Annecy, campagne
avril-mai 2009.
A shoal of small young-of-the-year perch in Lake Annecy
(Photo: J-L. BERTONCELLO)
- Lastly, maintaining fishing monitoring is fully
justified according to the experts, with a brief
annual report and a more comprehensive
assessment a few years later. More intensive
involvement of the Fisheries Scientific Committee
in the fishing management of Lake Annecy was
also recommended.
The Consultative Commission for Fishing
on Lake Annecy met at the start of 2011 and

3. LAKE BOURGET (f):
Assessment of practices for restocking lacustrian
salmonidae
LAke BOURGET (F)
Context
Tools
implemented
Author -
silmas
contact
• Marked eutrophication of the lake followed by major water quality restoration efforts
• Exploitation of salmonids by leisure and professional fishermen
• Support for the salmonids populations by stocking the lake with young fish at
various stages
• A full evaluation of these practices by marking the fish introduced
• Adaptation of the practices depending on the results obtained
CISALB – Sébastien CACHERA sebastien.cachera@cisalb.fr ; www.cisalb.fr
INRA Thonon-les-Bains – Alexis CHAMPIGNEULLE
alexis.champigneulle@thonon.inra.fr
A. EUTROPHICATION AND LAKE RANCHING
In the 1970s and 1980s, Lake Bourget experienced
a period of marked eutrophication with phosphorus
levels higher than 100 µg/l. This enriching of the
lake’s waters brought about a regression of the
populations of Salmonidae: Arctic char (Salvelinus
alpinus), whitefish (Coregonus lavaretus) and
lake trout (Salmo trutta), species sensitive to
environmental deterioration. Consequently,
fishermen were able to notice a drop in catches
for the first 2 species (Arctic char and whitefish)
that reproduced in the lake, which led to the
poor survival of eggs being blamed as one of the
production bottlenecks for these two species. For
trout, it was more the deterioration of the influents
and access to them which were implicated as being
the causes of poor and/or irregular restocking
of juveniles.
The environmental restoration approach, which was
recognised as being essential, was undertaken.
The management measures taken in the 1980s,
and particularly the creation of the discharge
tunnel into the Rhône, proved themselves to be
very effective as the phosphate content levels in
the lake’s waters fell substantially, going from 120
to 30 µg/l from 1980 to 1997.
At the same time, and until such time as the
beneficial effects of these “upstream” measures
could be felt on the trout and salmon populations,
over several decades, fishing managers carried out
a large number of diverse restocking operations
with a view to remedying the harmful effects of
deterioration of the fish habitat and in order to
respond to the growing demand for Salmonidae
for fishing and the restaurant trade. From the mid-
1980s onwards, finalised research efforts were
conducted with a view to assessing and improving
the effects of certain restocking methods.
This approach, which was called lake ranching,
is defined as follows. Lake ranching (restocking
the lake with juveniles) is one of the management
techniques for lake fisheries (natural lakes, storage
25

dams). In particular, it can be applied should there
be a lack of natural restocking with juveniles, or if
excessive fluctuations in terms of this have been
identified (diagnosed) as a major factor limiting the
level of the population and its production. What
is then involved is temporarily making up for the
shortcomings in the natural restocking through
the optimised, controlled release of juveniles
(in biological, technical and economic terms)
depending on the management objectives defined.
(Photos: CISALB)
Capture of whitefish spawners
Whitefish fry before release
B. DEVELOPMENT OF LAKE BOURGET’S WHITEFISH POPULATION
a. Fishing statistics
The annual catches made by professional fishermen
have been known since 1920. They enable an
initial estimate of fluctuations in the abundance of
the population. Whitefish catches dropped during
the eutrophication period. In the late 1980s, with
the start of lake ranching, the catches started
climbing once again, reaching an average of
10 tonnes per year between 2000 and 2008.
This resumption should also be linked to the
reoligotrophication of the lake’s waters, with the
phosphates content going from 120 µg/l to less
than 20 µg/l within 30 years. Since 2000, records
have been kept of whitefish catches by amateur
fishermen, and it has only been since 2008 that
they have become significant, exceeding a level
of 1 tonne.
It is probable that although the restoration of the
species was already well under way in the 2000s, it
was accelerated by 2 recent actions:
- In 2007, the legal catch size for whitefish went
from 30 to 35 cm (with the mesh size of the
pelagic nets used by professionals going from
45 mm to 48 mm) in order to preserve the resource
to a greater extent and thus enable young fish
to reproduce once prior to being caught;
- In 2008, a Prefectural Order banned the
consumption and marketing of whitefish from
the month of July, the start of the period of full
exploitation, due to PCB contamination. Additional
analyses enabled the Order to be lifted 6 months
later. Consequently, the 2006 generation was not
exploited during the summer of 2008 and widely
occupied the spawning grounds in winter. With the
concurrent development of regulations favouring
them, the effect of this event was to boost the
stocks, which currently seem to have taken on
a new dimension since 2009, with catches by
professionals reaching over 30 tonnes.

. Fishing yield (CPUE)
The yields achieved by leisure fishermen and
one-off fishing operations carried out in winter for
catching spawners confirm this development.
Development of the CPUE in terms of the number of whitefish
for amateur fishermen from 2004 to 2010
Development of catches of whitefish
spawners from 1989 to 2010
c. The effectiveness of lake ranching
• Development of releases of young fish
into the lake
Releases of young whitefish with a view to restoring
the populations began in the late 1980s. Over
the last 20 years, these releases have been
done based on different stages: fry at the vesicle
resorption stage, developing fry (who have begun
to consume dry feed in piscicultural conditions)
and fry that have reached an advanced stage of
fattening either under hatchery conditions or in
cages in the lake.
The Figure below summarises the number of fry
released since 1990. Major variability from year
to year will be noted both for the number of fry
released and the stages concerned at which
they were released. There were no releases of
fed whitefish fry (from spawners of Lake Bourget)
from 1980 to 1986. It was in 1987 that the first
trial releases of fattened fry (either raised in cages
or on granules) began, and they reached a level
of 100,000 in 1990-91. From 1992-98, they varied
from levels of 200,000 to 450,000.
It may be noted that the strong contrast between
the high level of stocking with young fish in
1999 (nearly 1 million developing fry and fattened
fry) and the lack of such stocking in 2000 is linked
to the absence of seed fish in 1999. The 2003
release was also low (approximately 25,000).
Since 2004, releases have mainly been made at
the stage when the fry have started to develop.
When the eggs harvest has been substantial, the
release associated with it is often split up, as was
the case in 1999, 2002 and 2008 (a mix of fry at
the resorption stage, developing fry and
fattened fry).
These variations from year to year in terms of
the quantities and the production stages of the
fry released come on top of the annual variation
factors for the number of eggs laid in situ as well
as the success of natural restocking.
Annual releases of whitefish fry at different
stages 1990-2007
• The effectiveness and yield of lake
ranching
The effectiveness of lake ranching was estimated
via marking campaigns. The first one was
conducted at the start of the lake ranching
programme and related to the marking of the
young fish stocking operations in 1987, 1989 and
1991. The second was conducted recently as it
related to the years 2003 to 2006.
During the first series, the marking consisted of
ablating the adipose or pelvic fin, with this being
carried out either on a batch of fry or on all of
the fry, depending on the year in question. The
27

second marking period profited from advances in
research efforts in the field of mass marking and
the various young fish released were all marked
using the otoliths fluorescent marking technique.
The marking methods will not be described in
this summary but are broadly outlined in various
articles and reports (CHAMPIGNEULLE, 2008;
MAGAGNIN, 2008). The Table below provides a
summary of the quantities, the type of marking,
and assessment of the effectiveness of ranching
over these two periods.
Marked otolith of whitefish (Source: INRA)
YEAR
PRODUCTION
TECHNIQUE
TYPE OF
MARKING
NUMBER OF
FRY RELEASED
(% MARKED)
RELEASE
STAGE
CONTRIBUTION
TO CATCHES
YIELD
(KG/1,000
OF FRY
RELEASED)
1990
Zooplankton/
cage
Ablation of the
adipose fin
101,150
(11%)
Fattened 80 % -
2003 Dry feed/tank
Fluorescent
marking
25,000
(100%)
Developing
R 0 %
S 0 %
-
2004 Dry feed/tank
Fluorescent
marking
180,000
(100%)
Developing
R 9 %
S 11-13 %
7-8
2005 Dry feed/tank
Fluorescent
marking
100,000
(100%)
Developing
R 11 %
S 8 %
2-2,5
2006 Dry feed/tank
Fluorescent
marking
320,000
(100%)
Developing
R 11 %
S 6 %
Assessment of the whitefish fry marking campaigns at Lake Bourget.
The contribution to the catches was assessed during the fishing season (marked S in the Table) and during spawner fishing
operations (marked R in the Table). The marked whitefish from the various cohorts in question were sampled from
the catches of both professional fishermen and amateurs.
Comparing the results of the first and second
campaigns cannot be envisaged as the release
stages and the type of production are not
the same.
During the first years of lake ranching, two marking
campaigns were conducted in 1987 and 1989 in
relation to a low number of released fry (between
10,000 and 40,000). These test campaigns
provided quite conclusive results in the sense that
the contributions were dependent on the number
of fry released and the yields were good overall,
being around 15 kg/1,000 fry released. In 1990,
the quantities released were more substantial as
they reached 100,000 fry. The marking carried
out made it possible to assess the contribution
of ranching as a proportion of the catches as
being 80 %.
During the recent period, the contributions may
be qualified as low regardless of the quantity
of fry released: 10 % on average. For 2 cohorts
at the end of exploitation (2004 and 2005), it
was possible to calculate a yield. The yield
was between 2 and 7 kg/1,000 fry released
depending on the year. In other terms, the end of
exploitation 2004 cohort enabled nearly 10 tonnes
of whitefish to be caught, of which only 1.4 tonnes
came from the 2004 release. For its part, the 2005
cohort enabled a total production of 2 tonnes, of
which 230 kg came from 2005 ranching.
These results show that the proportion
contributed by ranching to catches has
declined and that, on the other hand, natural
stocking has changed substantially over a
20-year period. Lake ranching has therefore
been very successful in restoring the whitefish
population in Lake Bourget and expansion of
the stocks now depends more on the success
of natural stocking. Currently, what remains
to be ascertained is whether lake ranching at
Lake Bourget will have to be maintained in the
years to come.

C. DEVELOPMENT OF THE POPULATION OF ARCTIC CHAR
a. Fishing statistics
In the late 1950s, catches completely failed and
remained next to nothing for 20 years, which is
the period during which the lake experienced
eutrophication. In the 1990s, catches gradually
increased in line with the reoligotrophication of
the lake and the execution of the lake ranching
programme. From 1995 onwards, they were
equivalent to the catches in the 1930s and 1940s.
Since 2008, a Prefectural Order has banned the
consumption and marketing of the char due to
PCB contamination. Consequently, catches by
professionals have fallen to nothing over the last
3 years. Amateurs’ catches, on the other hand,
were not halted as certain individuals continue to
fish for their own consumption needs, or practise
“no-kill” fishing.
b. Fishing yield (CPUE)
PCB Order of April 2008
The graph below shows the development in the
CPUE in terms of the number of char per drag
fishing trip from 1987 to 2010.
on the data from the volunteer fishermen, it is
possible to estimate the state of the fishing yields
based on chars caught that are larger than 30 cm,
legal size. Indeed, the CPUEs for the chars retained
(the green curve) have not been representative of
the fishing of adult chars since 2008 as a large
number of chars larger than the legal size were
returned to the water due to the PCB Order.
During a normal time, the overwhelming majority
of them would have been retained.
In spite of the major drop in catches in 2008
(PCB Order), the 2009 and 2010 CPUEs have
been maintained at a level close to that of the
best years.
c. The effectiveness of lake ranching
• Development of releases of fry
Inputs of eggs and fry from Lake Geneva were
carried out at a very early stage, but only from
time to time (8,000 fry in 1930 and 58,000 in 1940).
These efforts were intensified, particularly in the
1960s, but they did not enable the char fishery at
Lake Bourget to be supported. The releases were
then interrupted, and they resumed in 1982 and
1983 with 20,000 fattened fry and 6,000 autumn
fry respectively being produced from unidentified
eggs of Scandinavian origin. Releases of char fry
with a view to restoring populations really began
in the 1980s by using eggs taken from chars from
Lake Bourget or Lake Geneva.
Development of the CPUE in terms of the number of char
per drag fishing trip from 1987 to 2010
A group of twenty or so volunteer fishermen, who
have been monitored since 2004, have enabled
us to gain more specific details in relation to the
information gathered via mandatory catch books.
Thus, in spite of the PCB Order, which inevitably
has an influence on amateurs’ catch levels, based
Collection of arctic char eggs from Lake Bourget spawners
(Source: CISALB)
29

A distinction is drawn between three development
phases for char lake ranching:
- A ranching expansion phase (Phase 1:
1984-93): During this period, the level of
releases of Arctic char autumn fry gradually
went from zero to 150,000 autumn fry (34/ha).
The percentage of autumn fry from seed fish
caught in Lake Geneva fell regularly, going from
100% to 22% over the period of 1989-1993;
- A ranching phase at a high level (Phase 2:
1993-2002) during which, apart from 1999
(100,000), the annual releases fluctuated from
150 to 200,000 autumn fry, with the level targeted
being 150,000;
- A medium-level ranching phase (Phase 3:
2003-2008) during which the annual releases
fluctuated from 60 to 130,000, with an average
level in the vicinity of 100,000. In the 2002-2005
period, there was a gradual decline in ranching,
which went from a level of 150,000 to 60,000.
Annual releases of autumn char fry from 1984 to 2008
• The effectiveness and yield of lake
ranching
As is the case for the whitefish, the effectiveness of
ranching in relation to the char was estimated via
marking campaigns. Firstly, these made it possible
to assess the respective contributions of artificial
and natural restocking in char fisheries during
the initial (1985 cohort), middle (1990 cohort)
and recent (2003 and 2004 cohorts) phases of
reoligotrophication. The end objective aimed for
was to make a judgement about the development
of population supports depending on the marked
fish rate and therefore the development of the
contribution made by natural restocking. As a
supplement, these markings made it possible
to assess the restocking yield (kg of
catches/1,000 autumn fry released).
The Table below summarises the marking data
compiled since 1985.
Lake Bourget and the «Belledonne» massif
YEAR
1985
TYPE OF
MARKING
Adipose fin
ablation
1990 Fins ablation
2003
2004
Fluorescent
marking
Fluorescent
marking
NUMBER OF
FRY RELEASED
(% MARKED)
10,300
(100%)
92,500
(55%)
120,900
(100%)
90,000
(100%)
RELEASE
STAGE
Autumn fry
Autumn fry
Autumn fry
Autumn fry
CONTRIBUTION
TO CATCHES
R 35 - 40 %
S 25 - 35 %
R 55 - 90 %
S 50 - 90 %
R 60 - 90 %
S 75 - 85 %
R 60 - 90 %
S 90 %
Assessment of the char fry marking campaigns
R: Contribution to catches of seed fish
S: Contribution to captures in the fishing season.
In bold: Contribution to the dominant age category
AMATEUR
FISHING
YIELD
(KG/1,000
FRY)
PRO
FISHING
YIELD
(KG/1,000
YIELD)
TOTAL
YIELD
(KG/1,000
YIELD)
26 30 56
14 12 26
8.7 9.1 17.8
6.2 6.2 12.4

In 1985, the monitoring highlighted the great
effectiveness of the ranching carried out with fed
fry (autumn fry). Indeed, the quantities released
were very low, but even so, the contribution of
fry released in 1985 attained a level of 35 % on
average. In other terms, this release gave rise to
a good yield, namely 55.6 kg per 1,000 char fry
released. Moreover, the char produced by ranching
stayed around for a long time (up to stage 6+)
in terms of fishing, and as seed fish in
spawning grounds.
The study conducted during the recent period
shows that the contribution made by restocking
is still largely dominant within the context of char
production in spite of the reoligotrophication of
Lake Bourget. Thus, the stocks and the catches
stemming from this are greatly dependent on the
release of young fish carried out 3 years before
(cf. the Figure above). However, in spite of its
strong contribution, lake ranching seems less
effective than it was in its early days if you refer to
the yields calculated during the various periods.
For the 1990 cohort, the ranching carried out on the
one hand played an important role both in terms of
the fishery and in the fishing of seed fish, with this
applying to the 3 age categories (2, 3 and 4 years)
constituting the bulk of the catches. For 3-year-old
chars (the age category at which they are mature),
ranching makes a major contribution that is close
to 90 %. It can be stated that at the start of the lake
ranching, its contribution to the fishery as well as to
reproduction was an important one.
More recently, the development of mass marking
techniques (fluorescent marking) has enabled
a new assessment of ranching during the
reoligotrophication period. The last two marking
operations carried out in 2003 and 2004 showed
that ranching made a very strong contribution
to catches of fish and seed fish, amounting to
90 %. In other terms, only 10 % came from
natural restocking. The yields seem to be down
compared to the start of lake ranching as they were
18 and 13 kg/1,000 fry released respectively in
2003 and 2004.
These marking campaigns suggest that there was
a downward trend in the ranching yield between its
initial phase and the recent period. For example,
for the same release level of 90,000, there was a
lower yield in 2004 than in 1990.
Number of fry released from 1987-2010 and the CPUE
in terms of the number of chars per trip
This drop in the yield is perhaps related to the
change in the environment, trophic resources
(reoligotrophication) and fish stocking (the increase in
the stocks of whitefish, which is a trophic competitor
of the char’s, and the increase in pike (which is a
predator)). Recent catches by professional fishermen
do therefore have the same magnitude as during
the previous reference period (1920-1950), with
the exception that they are largely based on the
success of releases of young fish rather than on
natural restocking.
In spite of everything, even though it is low
(around 10 %), there is still a portion of the char
population that is the result of natural stocking. The
spawning grounds which contribute to this residual
functionality do however still have to be located, and
their characteristics need to be ascertained.
31

4. LAKE IDRO (i):
Evaluation and adaptation of fishing management
within a context of conflict between the various
categories of fishermen
LAKE IDRO (I)
Context
Tools
implemented
Author -
silmas
contact
• A high level of fishing pressure within a context of deterioration in the quality of the lake
• An ancient right enabling a high number of people living on the lakeshore to use quasiprofessional
fishing methods (nets) that greatly complicates fishing management
• Governance reinforced by setting up a Consultative Committee
• The implementation of strong protection measures for stocks and for reducing the
level of fishing pressure
Lombardy Region, General Directorate of the Environment, Energy and Networks
clara_bravi@regione.lombardia.it
Acknowledgement: this text was redacted with the cooperation of Mariapia VIGLIONE (Province of Brescia)
and Gaetano GENTILI (Province of Brescia’s external expert). Bibliography: Province of Brescia, Provincial
Fishing Plan, approved by DCP n. 1 in January, 31, 2012.
A. PREAMBLE
With regard to fishing rights, Article 137 of Regional
Law 31/2008 divides the aquatic environments
of the Provinces into categories A, B and C, as
well as public waters reserved for private use.
Category A refers to large water bodies like lakes,
with abundant, diverse fish populations which
constitute an economic resource for professional
fishing. The waters of Lake Idro (Lago d’Idro) fall
within this category and are considered to offer the
opportunity for quality fishing.
The Province of Brescia, which is the local authority
in the field of fisheries management, has sought
to use planning tools in order to consolidate the
ecological parameters of the aquatic environments
and in order to restore the habitats, so that the
ecosystem’s functional state can be ensured.
The authority co-ordinates direct interventions
in order to rebalance fish population and the
population of birds that prey on fish, and also
seeks to implement regulations for protecting

vulnerable species and supporting their
populations without however imposing rules
which would impose penalties on low-impact
fishing activities.
B. THE ENVIRONMENT AND FISHERIES ACTIVITIES
Lake Idro is an important site for leisure and
professional fishing. The town of Idro holds the
exclusive fishing rights for certain sectors of the
lake, while the inhabitants of the towns of Anfo and
Idro can exercise their “civic” fishing rights over
the whole water body, including the zone under the
jurisdiction of the town of Bagolino.
The holders of these “civic” fishing rights can use
professional equipment. In other words, they are
free to use professional resources, including nets,
without having the status of professional fishermen.
This right, granted to the inhabitants of these towns
several centuries ago in order to provide them
with the means to subsist, has become an
anachronism as well as a source of obvious
disparities and management issues. This “civic”
right is exercised over the whole lake, and the
equipment used is of professional quality.
The high number of potential users of this type
of equipment was becoming too great a source
of pressure, enabling an excessive number of
catches, particularly in the case of the most
sought-after species. The risk was worsened by the
gradual exhaustion of certain species referred to as
(Source: P. CUCCHI / P. CASTELLI)
being “noble”, that required optimal environmental
conditions, and which, at the same time,
were suffering from the deterioration of Lake Idro’s
water quality.
C. THE METHOD USED FOR RESOLVING THIS ISSUE
a. Regulations
For the whole of the Lombardy Region, the
regulations are based on Regional Law 31/2008,
which consolidates a series of texts relating to
agriculture, forestry, fishing and rural development,
as well as being based on Regional Decree
9/2003 (that has subsequently been amended),
which regulates and co-ordinates fishing rights at
regional level.
However, these regulatory measures do not factor
in the real “anomaly” relating to Lake Idro, namely
the large number of people who benefit from this
“civic” fishing right.
The provincial fishing plan proposed introducing
several restrictions, which are presented in
section c.
b. The consultative body for fishing
The Province of Brescia, which is the local
administrative authority responsible for the lake,
bases its decisions on the regional regulations and
on the provincial fishing plan, after receiving the
opinion of the Provincial Consultative Committee
for fishing.
This Committee, which exists in each of the Region’s
Provinces, was established pursuant to Article 135
of Regional Law 31/08, No. 10, which indicates that
“the Provinces must take charge of the establishment
of Provincial Consultative Committees for fishing.
These technical and consultative structures must
bring together the representatives of associations
of amateur fishermen, associations of professional
fishermen, fish farmers, environmental associations,
and fisheries experts who must provide
scientific opinions”.
Not only does this Committee represent the social
diversity of actors in the fishing sector, given the
skills areas of its members, but it is also capable of
proposing technical solutions to the various issues
which relate to the sector.
33

c. Actions taken and restrictions
imposed
With a particular focus on the “civic” fishing right
for the inhabitants of the two boroughs, studies are
currently being conducted in order to determine
what actions must be taken in order to make fishing
on Lake Idro compatible with good management of
the stocks, as required by the Regional Law.
With the help of the Consultative Committee, a
series of actions and restrictions were adopted in
order to ensure this compatibility. The restrictions
envisaged are as follows:
- Banning setting nets in the northern part of
the lake (in the zone belonging to the town of
Bagolino near the mouth of the River Chiese,
which is an important spot for Salmonids fishing),
and only permitting access to line fishing for
leisure purposes;
- Limiting the size of the nets that the holders of a
“civic” right can use, in order to distinguish them
from real professional fishermen who actually pay
costs relating to compulsory insurance and social
security contributions, as well as the costs related
to processing and marketing their catches;
- Limiting the period during which fishing in boats
is allowed;
- Selecting which catch equipment is compatible
with the preservation of fish in their juvenile phase;
- Banning or limiting the catching of
endangered species;
- Banning fishing during spawning periods
and banning the catching of fish which are not
yet mature.
These measures were decided on based solely on
technical criteria, particularly for regulating fishing
periods and the resources granted (the nets’ size
and mesh). These rules stem from knowledge
of the biology of the species of fish in the very
environment where these restrictions are applied.
In particular for the first measure, the specific
environmental features and a special request
from the town of Bagolino made it possible to
define a zone where a ban was implemented on
all “intensive” techniques, such as the use of
nets, with the sole objectives being to reconstitute
stocks and preserve piscicultural resources. Only
leisure fishing is allowed.
Fishing from boats is allowed only outside a zone
around the mouth of the River Chiese at a distance
of at least 30 metres from the shore. Fishing from
boats in authorised sectors begins only on the last
Sunday of March.
The Province of Brescia has also made
administrative and technical commitments for
setting up monitoring of fisheries activities and
the reconstitution of stocks. Restocking of the
lake is carried out both based on purchasing fish
for restocking it and via economic support to local
fish farmers who release fish born in fish farms into
the lake.
(Source: P. CUCCHI)

D. RESULTS: SUCCESSES AND DIFFICULTIES ENCOUNTERED
As the plan is still being implemented, the actions
recently undertaken have not yet had any immediate
major effects. To date, the only visible benefits are
“cultural”, and relate to the establishment of the
Consultative Committee, whose participants had
until then been involved, but as part of a complex
decision-making process.
The main difficulty encountered stems from the
fact that no group is usually ready to renounce
privileges that it has inherited from the past and
that it appreciates, even if the environment and the
fishing conditions have deteriorated since then.
E. CONCLUSIONS
Several lessons may be drawn from the experience
of Lake Idro, and these are summarised as follows:
- The existence of a system involving “perks”
like civic fishing rights makes management very
difficult, because the main variable is beyond
the control of the structure in charge of fishing
management (the Province);
- Use of a Consultative Committee enables all
the actors to take part in a complex decisionmaking
process. The presence of outside experts
is useful for the technical study of specific
situations, and facilitates the adoption of the most
relevant solutions;
- The establishment of regulated fishing sectors
or periods is one of the methods used to
reduce conflicts;
- As the chemical properties of the lake water vary
with the changing seasons, the fish populations
can experience considerable changes over the
years. The difficulty of assessing the level of
productivity is a factor common to all peri-alpine
lakes. For Lake Idro in particular, fish stocks
variations over the last 10 years and the speed
of change suggest that a detailed technical
assessment may need to be carried out at least
once every 5 years. Periodic checks would thus
enable the catch sizes to be adapted, the catching
of certain endangered species to be banned, and
the types of nets allowed to be limited. The mesh
size must vary depending on the species and the
age categories to be protected;
- Generally speaking, the regulations must be
flexible and easily adaptable depending on the
state of the fish populations.
35

5. LAKE BOHINJ (slo):
Regulation of fishing and other leisure activities
within a context of strong environmental
preservation
Lake Bohinj (Source: D. TOME)
LAKE BOHINJ (SLO)
Context
Tools
implemented
Author -
silmas
contact
• A lake located in a national park
• A ban on boats with thermic engines
• Regular development of regulation of the various types of use, including fishing,
in order to adapt to new practices
National Institute of Biology – NIB
anton.brancelj@nib.si ; tina.leskosek@nib.si
Certain parts of this presentation are taken from the Triglav National Park management plan.
A. TRIGLAV NATIONAL PARK
Triglav National Park is Slovenia’s only national
park. It is named after the highest mountain right
in the centre of the park, which is also Slovenia’s
highest peak (2,864 m). Its etymology remains
unclear: Triglav (which can be translated as “threeheaded”)
owes its name to its characteristic shape
when viewed from its south-eastern side, or to the
fact that the highest Slavic divinity was supposed
to have his throne on top of the mountain. This
summit is a national symbol featured on the
national flag and crest.
Triglav National Park stretches from the Italian
coast to the Austrian frontier in north-west
Slovenia, which is itself located south-east of the
Alps. The park covers a surface area of 880 km²,
which amounts to 4 % of Slovenia’s territory. It is
also the most eastern European park, and has been
protected since 1924. The main mission of the
Triglav National Park Public Institution is to protect
it; research initiatives have also been undertaken
(http://www.tnp.si/national_park/).

B. THE PROTECTION ZONE AND USAGE-RELATED ISSUES
The park is divided into three protection zones.
In the first two, priority is given to preserving the
environment, even though in the second zone a
few traditional economic and tourist activities are
authorised. In the third zone, people can live and
work in accordance with the park’s regulations.
It is prohibited to swim, dive, sail or carry out
any other sports activity in lakes and rivers in the
first two protection zones. Although it is located
in the last one, Lake Bohinj is an exception,
as swimming, diving, winter skating, boating
and sailing are allowed.
the passage of the electric boats can stir up
sediments on the lake bottom;
- There is no specific launching area; there is
unrestricted access to the lake;
- In relation to electric propulsion, there is no
specific regulation about what type of boat may
or may not be authorised.
The following presentation illustrates a few
conflicts between the park’s regulations, which
are oriented towards environmental protection,
and certain leisure or socio-economic activities
carried out, including fishing.
a. Boating
Users can use oars, canoes, kayaks, small yachts,
and two electrically-powered tourist boats. Boats
with internal combustion engines are prohibited,
but there is no particular restriction on the use
of electric motors, and at the time of writing
anyone can do boating with them. Nevertheless,
certain questions and issues are raised regarding
their use:
- Jetties should be installed for these boats;
- Certain Organizations emphasise the fact that
Electric touristic boat on Lake Bohinj
(Source: D. TOME)
37

. Swimming
At the time of writing, swimmers can swim all over
the lake, but the pressure and the number of users
is too high in summer. What those living on the
lakeside and experts want is to direct swimmers
to certain zones along the banks, as well as raising
the awareness of these visitors, which would
enable man-made impacts on certain banks to be
reduced significantly:
- Reduce the negative impacts of swimming on the
banks of Lake Bohinj;
- Without banning swimming in the lake;
- And without limiting access to the lakeshores.
c. Ski slopes in the catchment area
There are ski slopes in the catchment area upstream
from the lake. Due to the park’s regulations,
producing artificial snow is not permitted.
Numerous problems and conflicts of interest are
related to this activity. Skiing professionals would
like to be able to produce artificial snow, which
would extend the effective skiing season.
d. Road traffic
There is too much traffic around the lake. Visitors
park all over the place in spite of fines applying.
The large number of cars and motorbikes is
harmful to the lake and the surrounding sectors.
Exhaust fumes pollute the air and trees; fuel and oil
spills and stains are a serious threat to the soils and
water. Several measures have been undertaken or
are about to be in order to limit the parking areas to
the lake’s immediate vicinity.
Level one: 2006-2007 regulations
- Informing visitors about the traffic regulations
around Lake Bohinj;
- Carrying out a study about the possibilities of
reducing traffic.
Level two: 2007-2013 regulations
- Guaranteeing that there is a sufficient
number of parking spaces beyond the lake’s
immediate vicinity;
- Establishing a public transport network;
- Granting those who live on the lakeside
priority parking.
e. Fishing
There is a specific regulation for fishing on
Lake Bohinj and its tributaries (Sava Bohinjka
and Mostnica). Certain points are provided in
detail here; for further information, you need
to contact the Bohinj fishing association
(http://www.bohinj.si/rd).
- Fishing is allowed on the lake and its tributaries
(Sava Bohinjka and Mostnica);
- In addition to annual licences for members of the
fishing association, it is also possible to pay for
tourist licences;
- Lake fishing is only allowed in relation to certain
species, and only using certain types of bait;
- Drag fishing is permitted from the shore or a boat;
- From the shore, you are only allowed to use a
single rod fitted with just one hook per lure;
- Members of the Lake Bohinj fishing association
can catch 5 kg of fish per day, consisting of
different species. For tourist licences, the quotas
are also limited and are printed on the licences;
- Catching frogs, molluscs, crayfish, or any other
aquatic animal is prohibited.
Grayling and Chubb on the shore of Lake Bohinj (Source: ZZR Slovenia)

C. DEVELOPMENT OF THE REGULATIONS
It has proved possible to resolve some of the issues
referred to by implementing new park regulations
in 2010, the objectives of which are:
- To define a precise framework for swimming,
boating and leisure practices depending on types
of usage, and on the use of the lakeshores, etc.,
- To install suitable equipment (moorings,
jetties, boatsheds),
- To specify boating rules,
- To define a strategy for invasive species in the
park, depending on their impact on native
species, and to prepare measures for eliminating
them or limiting them.
Certain restrictions are also applied to the first and
second protection zones, as well as to outstanding
natural heritage zones: a ban on construction, and
controlling traffic in order to limit it.
These regulations also take into account the
principle of not building and of refraining from
developing new cycle paths in the first and second
protection zones, as well as in outstanding natural
heritage zones and in their catchment areas.
Provisions have been applied in order to limit
traffic, particularly in the first and second protection
zones. Vehicles are only allowed to stop and park
in the third zone (and subject to conditions in the
second zone, outside natural heritage areas).
Lastly encouragement is given to raising the
awareness of the inhabitants and visitors regarding
nature conservation, through information points
and centres within the park.
39

© B. CLAEYSSEN
IV. Presentation
of interesting
feedback within
the partnership –
habitat restoration
actions

1. LAKE ISEO (i):
Restoration of fish habitats by submerging physical
structures
LAKE ISEO (I)
Context
Tools
implemented
Author -
silmas
contact
• Deterioration of the lake’s water quality (eutrophication) and of the littoral
habitats (control of the level), which occurred mainly during the second half of the
20th century
• The “Lake Contract” procedure for taking action regarding the various types of
pressure exerted on the aquatic environments
• Restoration and diversification of fish habitats by submerging wood-based physical
structures within them (whole trees, bundles of wood, etc.)
ERSAF - Ente Regionale per i Servizi all’Agricoltura e alle Foreste Ufficio di Milano
livio.mallia@irealp.it ; www.ersaf.lombardia.it
A. CONTEXTE
By setting objectives for sustainable water
management, the regional government of Lombardy
has identified that concerted planning tools were
the best way of promoting consultation in the fields
of water use, planning, and conservation policies,
by encouraging the participation of public and
private structures.
Among the numerous projects targeting Lake Iseo
and its surrounding area, from 2004 to 2006 the
Coordinarsi Agire Insieme sulle Acque del Sebino
programme (“Let’s co-ordinate ourselves to work
together on the waters of Lake Iseo”) identified
the actions required for achieving a high level of
environmental quality and effective management of
the lake’s waters.
This programme was one of the first concrete steps
towards a global strategic vision for the construction
of an Organizational system which could bring
together all the stakeholders, to establish a network
of contacts and actions which may help in launching
a Decision-Making Steering Committee 1 .
1
It optimises efforts and minimises the overlapping of actions, whilst at the same time maintaining the autonomy of each structure’s responsibilities;
and develops an information and communication system (Web site) for the technical elements and general intervention directives. The Steering
Committee has three objectives: implementing actions, collecting funds, and promoting discussion and collaborative efforts in order to implement
joint policies, as opposed to isolated interventions.
41

The project’s final action was to define and approve
a “Lake Contract” 2 which enables:
- “A set of rules to be adopted in which the criteria
of public interest, economic performance, social
value and environmental sustainability play
an equal role in seeking effective solutions for
restoring the lake’s environment”,
- Promoting, based on the content of Directive
2000/60/EC, the “consultation and integration
of policies at the level of the lake’s catchment
area, with the participation of all the public and
private entities in the protection and optimisation
of water resources and of related habitats, as well
as reducing the risk of flooding”,
- Developing an activities plan summarised in
the Strategic Document for Lake Iseo 3 , for
long-term interventions, shared by everyone, for
improving and dynamising the local territory.
The Strategic Document for Lake Iseo contains
an initial analysis of the territory, and of the
environmental and socio-economic stakes
affecting the lake. Three main issues have
been identified:
- The eutrophication of the lake;
- The collection of wastewater and treatment of it;
- Control of the lake level.
These issues must be resolved in order to achieve
the objectives set out in the regional law relating to
water protection and use 4 .
B. THE MAIN ENVIRONMENTAL ISSUES
As far as eutrophication is concerned, an analysis
of the pollutants in the lake provided an estimated
pollution load of 72 tonnes of phosphorus per year,
which is the equivalent of a balanced phosphorus
concentration of 16-18 mg of phosphorus per litre,
which can be achieved in 5 to 10 years.
The drop in the concentration of the pollutant
loads flowing into the lake is the result of efforts
devoted to wastewater collection and treatment,
which began in the second half of the 1990s. The
Valcamonica sector (from which wastewater flows
into the River Oglio) and certain buildings from
which wastewater flows in the Borlezza sector do
not yet have a treatment system.
Another major issue is controlling the level of
the lake. The lake waters are an energy source
(hydroelectricity) used for irrigation purposes as
well as for industrial uses throughout the catchment
area. The lake’s outlet at Sarnico must therefore
be controlled on a seasonal basis. This leads to
major variations in the lake’s level. In particular, low
levels give rise to problems for public and private
boat traffic, damage the lake ecosystem, cause
structural problems in a large part of the littoral zone
belonging to boroughs on the edge of the lake, and
contribute to the emergence of mud flats and the
draining of sectors featuring aquatic macrophytes
(with a negative impact on the landscapes and
the lake’s recreational value). To the contrary,
excessively high levels cause local flooding, make it
difficult to moor boats along wharfs, cause damage
to public and private property, problems for boat
traffic, and water seepage into the wastewater
collection networks.
Resolving these issues is a long-winded process
which, moreover, would enable the resolution of
other related disturbances:
- The proliferation of microalgae which, in late
summer, can cause temporary bans on swimming
and using the lakewater for irrigation purposes.
These proliferations take the form of red stains on
the surface of the water. There are also possible
consequences for the borough of Monte Isola,
as its drinking water supply comes directly from
the lake;
- The loosening of aquatic macrophytes from the
bottom of the lake, which then float to the surface
and are carried downstream by the current.
There are negative impacts on tourism, fishing,
and for pipes, and they are likely to cause costly
management problems;
- Disturbance of the ichthyofauna, which feels
the negative impact of eutrophication and
fluctuations in the lake level.
2
A voluntary agreement between the regional government, local authorities, and other public and private structures aimed at defining objectives,
intervention strategies, responsibilities, and the actions which will be initiated.
3
The Strategic Document for Lake Iseo was one of the main achievements of the “Coordinarsi Agire Insieme sulle Acque del Sebino” programme.
The document’s objectives were an analysis and summary of the state of the territory, environmental and socio-economic issues affecting the lake
region, and drawing up a list of 80 actions for protecting, optimising, promoting and developing the lake, in compliance with the existing planning
documents and in accordance with the local needs which emerged during the participatory process.
4
Regional Government of Lombardy DGR VIII/2244 of 29 March 2006 entitled “Approval of water protection and use, in accordance with
Art. 44 of Legislative Decree 152/99 and Art. 55, section 19 of Regional Law 26/2003”, which is the benchmark law for all operations contributing
to achieving quality objectives in Lombardy.

C. THE SOLUTIONS IMPLEMENTED
The 80 actions and measures identified in the
Strategic Document for Lake Iseo, particularly
via contributions from the various levels of local
bodies, were divided into two major categories:
general measures, which concern the whole of
the Lake Iseo region and which are partly linked to
planning at provincial and regional level, as well as
specific measures targeting local issues.
The projects and operations launched to date,
the overall cost of which is €2,100,000, and
which benefit from a €1,260,000 subsidy from
the Fondazione Cariplo, were approved by the
Steering Committee.
The “Coordinarsi par Agire Insieme sulle Acque
del Sebino” project contributed to the fulfilment
of the environmental objectives set by the
Water Framework Directive, particularly as far
as knowledge and management of water quality
are concerned, as well as participation of the
various stakeholders, the development of the
tools required to implement concrete actions and
targeted interventions aimed at the priority stakes
identified by the local population.
The project for the restoration of Lake Iseo’s
aquatic ecosystem and its natural habitats,
conducted from 2008 to 2011 (cost: €845,000,
€450,000 of which come from cofinancing), led to
the completion of numerous actions and
interventions aimed at:
- The restoration and recolonisation of the
indigenous species in degraded sectors, the
diversification of aquatic habitats, protection of
remaining heritage habitats by optimising them
and enlarging them, and improving the value
of the ecosystems in the downstream part of
Lake Iseo;
- Interventions aimed at expanding the system
for monitoring the quality and quantity of the
wastewater discharged into the lake;
- On-line promotion of communications and
activities for raising awareness, as well as
training and education actions, and project
co-ordination activities.
The project entitled “Integrated interventions
aimed at improving the ecological conditions,
the qualitative state and the restoration of Lake
Iseo habitats (2011 to 2013)”, which has
an estimated cost of €1,000,000, contains
the solutions proposed, some of which have
already been undertaken. This project is divided
mainly into four sections:
- The restoration of the aquatic ecosystems of both
the lake and its natural habitats, in order to restore
degraded zones, facilitate their recolonisation by
native species, protect existing heritage habitats
by optimising them and expanding them, and
improving the value of the ecosystems in the
downstream part of Lake Iseo;
- Interventions aimed at expanding the system
for monitoring the quality and quantity of the
wastewater discharged into the lake, functional
assessment of the restoration actions, and
improvement and expansion of the monitoring
techniques for identifying the interventions
required for the treatment of the catchment area’s
wastewater;
- Identification and optimisation of sectors that are
productive in terms of resources;
- Educating, raising awareness and implementing
technical training activities.
To sum up, the actions planned fall under
three categories:
- Direct interventions (works);
- Management actions (functioning and/or
management tools);
- Harmonisation of governance tools.
D. DETAILS ABOUT THE PROJECT
The first interventions began in April 2008; they are
being continued with a series of stages depending
on the level of priority and the specific needs of
each site.
The most important environmental issues to be
resolved are the physical changes to the habitat,
such as dams and artificial embankments,
environmental changes due to activities such as
artificial control of the lake level, influxes of polluted
water, dredging operations (generally every 5
years, the main impact of which is a reduction in
the water’s transparency), and cutting reed beds.
The methodologies used at specific intervention
sites, which were moreover proposed in previous
scientific studies, are the result of implementation
of environmental engineering techniques such
as rehabilitation of the littoral, restoration of
the bottom of the lake in order to encourage
the diversification of aquatic habitats, and the
implementation of “nursery” techniques in order
43

to replant the littoral’s vegetation and expand reed
beds so that new spawning areas for fishes and
birds can be created.
(Photos: R. BENDOTTI)
a. The interventions carried out
- Completion of habitat restoration works in the
Sarnico and Predore sectors, with the submerging
of a total of 160 bundles of branches and
12 whole trees;
- Completion of 90% of the dredging and
hydraulic cleaning operations in the Sarnico zone
(11,500 m 3 worth of materials moved);
- Creation of 110 m 3 of submerged reefs, used
as refuges for fish and in order to protect the
beaches in the Sarnico sector;
- Creation of 850 m 2 of new beaches for the
reproduction of target species of littoral fish, such
as the shad, the bleak and the whitefish, in the
Sarnico sector;
- Submerging 36 small trees in order to encourage
the colonisation and reproduction of certain
species of fish in the Iseo and Predore sectors;
- Submerging 40 large trunks and branches in
order to create a new habitat suitable for
colonisation by large predators (such as pike) in a
sector near Iseo;
- Restoration of the historic eel fishery at Sarnico
- Paratico (removal of damaged infrastructures,
submerging 51 new posts, planting of 46 trees,
submerging 50 m3 of backfill, and of 115 fascines
of branches in groups of 5);
(Photos: R. BENDOTTI)

(Photos: R. BENDOTTI)
- Start of the construction of small artificial islands
by filling their wooden support infrastructure, in
the Sarnico region.
(Photos: R. BENDOTTI)
45

. Interventions in progress
- Creation of 150 m 2 of new beaches for the
reproduction of target species of littoral fish such
as the shad, the bleak and the whitefish in the
Paratico region;
- Submerging 80 fascines of branches in order to
facilitate the egg-laying of target species of fish
(such as the European perch) in the Sarnico zone;
- Completion of artificial islands (4,000 m²) planted
with reeds and ligneous species, thus providing
a habitat for birds, spawning zones for fish, and
featuring a pebble bed with fascines of branches
along with the completion of restoration works in
the Sarnico and Iseo sectors;
- Dredging in order to improve the hydraulic
evacuation of Lake Iseo at Sarnico and Paratico,
covering a total surface area of 10,000 m²;
- Hydraulic dredging of the littoral covering a total
surface area of 10,000 m² within a sector of
Lake Iseo;
Fascines of branches being submerged
(Photo: R. BENDOTTI)
- Hydraulic cleaning of the lake’s littoral in
targeted locations, covering a total surface area
of 3,000 m²;
- Communication: Expanding the database and
development of the www.lagoiseosebino.it
web site.
E. EVALUATION OF THE INTERVENTIONS
These actions are the result of monitoring efforts
both prior and subsequent to the interventions, with
a view to evaluating their functionality.
The post-works evaluation is under way, so that the
colonisation of the new habitats can be assessed,
along with the impact of the interventions on the local
dynamics of the ecosystem.
Lastly, automatic instruments were used in order
to gather quantitative and qualitative data on the
influxes of wastewater into the River Oglio upstream
from the lake and in the municipality of Costa
Volpino, and in order to gather data concerning the
physical, chemical and biological characteristics of
the lakewater.
In light of the extremely complex nature of the project,
the new fields of intervention, the lack of time that
has gone by since the actions were initiated, and the
various interests at stake in these sectors of the lake,
for the time being it is difficult to provide a reliable
evaluation of the effectiveness of the project.
The first interventions, relating to the environmental
issues which were initially identified, and the
ecological needs of the target species of fish, were
carried out in several littoral and sub-littoral zones at
Lake Iseo. Particular attention was devoted to species
of major economic value, adopting a conservation
perspective, with the objectives being to improve the
reproduction success rate and the availability of a
habitat that is suitable for fishes.
Even taking into account the benefits for the
ecosystem related to the implementation of each
action, the initial damage to the lake bottom habitats
undoubtedly caused a certain degree of deterioration
to the overall ecosystem, and therefore it would be
premature to state whether the interventions carried
out will produce the end results expected.
There is a high probability however that a combination
of meticulous regulation of the lake level and the
installation of submerged fascines will facilitate fish
reproduction, which comprises a first step towards
improvement of the ecosystem.
It will certainly be interesting in time to evaluate
the results of the monitoring plan set out in
the project for «Restoration of the aquatic
ecosystem of Lake Iseo and the natural habitats”,
in order to evaluate the functionality of the
interventions in light of a full biological inventory
over a cycle involving at least one year following
completion of the activities, featuring the
following in particular:
- An evaluation, carried out by diving, of the
conservation and of the scope of the submerged
habitats created by the project;
- An evaluation of the level of colonisation of these
new habitats;
- Monitoring of the influence of these interventions on
the local macro-physical dynamics.

2. LAKE SERRE-PONÇON (f):
Project for the creation of experimental spawning
grounds within the context of an artificial lake with
major fluctuations in water levels
LAKE SERRE-PONÇON (F)
Context
Tools
implemented
Author -
silmas
contact
• A large artificial lake subject to major fluctuations in water levels
• Strong fisheries demand in terms of species whose natural reproduction is impacted
by changes in the lake levels, and is dependent on the development of aquatic
plant habitats
• Seeking out experiments conducted in similar contexts
• Drawing up a project for the creation of experimental spawning grounds subsequent
to advanced field reconnaissance
Syndicat Mixte d’Aménagement et de Développement de Serre-Ponçon - SMADESEP
f.gleize@smadesep.com
A. CONTEXT
The programme entitled “Development of fishing
activity on Lake Serre-Ponçon” was initiated by
the SMADESEP 5 in October 2007, with a projected
budget of €142,000. Among the development
avenues envisaged (creating access to the water,
parking areas and boats storage, paths and
fishing stations, etc.), one is oriented towards the
development of semi-natural spawning grounds
(and relates to a budget item of €23,000).
This technical development orientation is based in
particular on the conclusions of a study carried out
under the project management of the Département
Fishing Federation: “What solutions are there to
adapt for developing pike egg-laying supports
in the area affected by water level variations in
Serre-Ponçon?” 6 .
As a reminder, Lake Serre-Ponçon is placed in the
second fishing category (Cyprinidae are dominant),
and is the subject of a fishing Order specific to
large inland lakes: it hosts fifteen or so species of
fish, including three indigenous ones (see the Table
on the following page).
And yet, the special characteristics of Serre-Ponçon
have harmful consequences for the reproduction of
phytophilic species (particularly the pike, which in
order to lay, needs a shallow substrate consisting
of plants): due to the physical constraints involved
in the rapid level fluctuations of the lakewater,
phytophylic species are not adapted to the egglaying
supports, due to the absence of vegetation.
In plain language, spawning ground sites are rare
there, which preconditions the vulnerability of
the species due to the absence of protection for
juveniles, blockage of access to spawning grounds,
the major risk of the ovules ending up above the
water line, etc.
5
SMADESEP – the Serre-Ponçon Development Public/Private Entity – consists of local lakeside bodies responsible for containment works and the
General Council of the Hautes-Alpes. It is extending its area of authority both into tourism and environmental fields.
6
RUHL, Cyril, 2003/2004, Fédération des Hautes-Alpes pour la Pêche et la Protection du Milieu Aquatique.
47

SPECIES LATIN NAME 1970 1978 1983 1996 2007
Lake trout Salmo trutta fario * + + + P
Rainbow trout Onchorynchus mykiss P* P
Arctic char Salvelinus alpinus P* P
Whitefish Corégonus sp. P* +
Pike Esox lucius P* P + +
Bream Abramis brama P* P
Bleak Alburnus alburnus P P ++++ ++++
Common barbel Barbus barbus + + P P
South-West
European nase
Chondrostoma toxostoma ++ ++ + ++
Carp Cyprinus carpio * P P P P
Gudgeon Gobio gobio * + + + +
Chub Leuciscus cephalus ++ + + +
Common dace
Leuciscus leuciscus
Souffia Telestes souffia P P
Minnow
Phoxinus phoxinus
Roach Rutilus rutilus * ++++ ++++ ++++ ++++
Rudd Scardinius erythrophthalmus * P P P
Tench Tinca tinca * P P P P
Eel Anguilla anguilla P P
Perch Perca fluviatilis * ++++ +++ + +++
Bullhead
Cottus gobio
Freshwater blenny Salaria fluviatilis ++*
NUMBER OF SPECIES 7 15 12 17 16
Key:
Abundance classes from + to ++++
P: Species present, but with very
little representation, or limited to a
geographic sector
*: Introduction
(Source: CHAPPAZ, 2009)
Only one natural spawning ground that was
really operational at the time of writing has been
identified in the Le Liou sector (Crots and Baratier
towns): it covers a surface area of approximately
80 ha between an elevation of 770 m and 780 m,
along the Crots dyke.
Frequentation of bream, carp and pike at the Le Liou spawning ground (June 2011, SMADESEP)

The pike, which is a higher-level predator, is a key
species for the good health of the Serre-Ponçon
lacustrian ecosystem: it controls the development
of the other species (particularly the bleak and
the roach) which, due to their major development,
can have a strong impact on fisheries resources
(reduction in biodiversity, reinforcement of the
phenomenon of eutrophication, etc.). Within
a regulatory context which consists of
guaranteeing the Serre-Ponçon MEFM
(Greatly Modified Water Body) good ecological
potential by 2015, actions favourable to the natural
reproduction of pike within the containment works
were therefore targeted in partnership with the
Département Fishing Federation of the Hautes-
Alpes. In addition to its ecological role, it is also
a species of high value in terms of fisheries (along
with trout, it is the most prized species in the
containment area).
The stake involved in the experiment therefore
consists of identifying the processes and sites
with characteristics favourable for the spawning
of phytophilic species, subject to the proviso of
implementing vegetation planting actions.
In winter, the water level variation phenomenon
subjects the emerged surface areas to frosts to
a depth of several centimetres, thereby
destroying the riparian fauna and preventing
any establishment of aquatic plant habitats.
Surface areas exposed by the water level variation during the
winter period (aerial photo – February 2011, SMADESEP)
Consequently, the water level variation is the
main factor limiting the plant development of the
containment banks.
The experiment’s principle thereby consists
of accelerating a vegetation recolonisation
process (by establishing plants resistant to the
submergence and exposure phases relating to
the changing water levels and maintaining
sufficient humidity required for plant life to develop),
with the essential condition being the presence of
a long-term or even permanent waterway in order
to ensure a favourable hydraulic cycle.
B. TECHNIQUES FOR ARTIFICIAL DEVELOPMENT OF SPAWNING GROUNDS
The study then goes on to present proven
techniques, used today for maintaining water in
shallow basins, as well as for the preservation and
protection of banks subject to marine and river
erosion due to wake waves which, following tests,
would enable the development and creation of
spawning grounds under optimal conditions.
An example of implementation in a maritime
environment:
This technique consists of capturing part of the
water from a stream, and then creating containment
works within a pocket of water limited by a curved
bar, which can be manufactured or created in
situ. The principle of this bar is to match the relief
lines so that it rises up slightly at the ends, whilst
consisting of a “high-strength textile sleeve” filled
with alluvial materials, shaped like a flattened inner
tube spread out on the bed.
49

At Serre-Ponçon, the principle implemented would
thus consist of placing a geotube and then covering
it with a geotextile membrane, so that a 80 - 300 kg
rip-rap can be laid on top of it that can withstand
wake waves (3H/1V).
The bar/tube and the pocket of water created would
then be partially planted with suitable vegetation
(Carex hirta, Carex stricta, Phalaris arundacea,
Phragmites australis, Ropippa sylvestris), and even
commercial trees and shrubs that are also suitable
(willows, poplars, alders, etc.).
The tubes would be laid out in lines so that the
h = 0.30m to 0.50m:
1. Manufactured items: “Geotube” type sleeves
laid out/aligned in situ and filled by pumping alluvial
material in the lake.
2. Creation in situ: Execution and placement of
geotextile sleeves by turning them over and burying
them in trenches that are 0.50m to 0.70m deep and
filled by pumping alluvial materials into them.
To this end, the vegetation planting experiment
conducted by SMADESEP on the tail of the
Serre-Ponçon containment works under the
framework of nautical development works on the
Chadenas Plateau enabled the suitability and
strength of certain types of these plants to be
tested. Feedback has to be obtained from the
sub-contracting company in order to determine a
vegetation planting protocol that can be applied to
other sectors.
Propagation using cuttings of willows and carexes planted on backfill on the tail of the containment works under
the framework of execution of works for the Chadenas channel (October 2010, SMADESEP)
C. POTENTIAL SITES FOR THE DEVELOPMENT OF ARTIFICIAL SPAWNING
GROUNDS AT SERRE-PONÇON
The conditions for restoring and developing
spawning grounds are linked to the presence of
water and permanent humidity enabling good,
rapid plant recolonisation.
The choice of experimental sites must therefore
take these imponderables into account, as well as
fulfilling the 5 criteria identified in RHUL, 2004:
- A substantial humidity rate, guaranteeing a
good humidity level for the plants. Sites in the
proximity of permanent influents must therefore
be given priority;
- A gentle topography (selection of a site with a
gentle slope) enables the risks of soil leaching
due to wake waves to be limited, as well as
enabling humidity to be maintained for a longer
time during periods when the land is above the
water line;
- An altitude of between 773 and 780 m NGF
(French General Levelling System), with the pikes
spawning in shallow zones in June and with
vegetation that is “adaptable” to variations in the

water level and which cannot withstand being
submerged at depths exceeding 7m;
- Major luminosity, with the plant species in
zones subject to variations in water level being
heliophilous, and therefore requiring a large
amount of sunlight;
- Low human frequentation in order to limit
trampling of the zones to the maximum extent
possible as well as to ensure that the spawning
species have as much peace as possible.
In the study in question, possible experimental sites
for artificial spawning grounds were recommended
at the mouths of the Réallon Stream (Savines le
Lac) and the Boscodon Stream (Crots), at Les
Chappas (Pontis), on the tail of the Embrunais
containment works and on the Chadenas Plateau
(towns of Crots, Baratier and Embrun). These
sectors were recognised as part of a field inspection
carried out in autumn 2009 (Michel DELENATTE,
David DOUCENDE, Frank GLEIZE) in order to
check the potentialities in terms of adaptability for
spawning grounds.
Even so, and for various reasons, these sectors
have not proven themselves to be particularly
suitable for the development of artificial spawning
grounds:
- The Le Liou zone (identified as experimental
sector No. 1) is fed by a permanent waterway
which very recently (and therefore quite late
in relation to the initial project) enabled the
development of a vegetation support within the
sector. The growth of vegetation now established
is not encouraging the SMADESEP and the
Département Fishing Federation to install
man-made infrastructure there, as the natural
phenomenon is enough in itself. Moreover, as
this sector is particularly sensitive in the event
of high water levels, the financial investment in
infrastructure that is particularly susceptible to
it should be limited. As it is the only functional
natural spawning site on the containment works,
it should be safeguarded as a matter of priority
due to its functionality: in this capacity, some
slight development work could be carried out,
such as placing blocks enabling the stream
to meander more (in order to optimise the soil’s
humidity content).
- The mouth of Le Réallon (identified as
experimental sector No. 2) did not seem very
suitable either for the placement of this sort of
tube. Firstly, because it would be necessary to
reroute part of the stream in order to create a
“wetland zone” at the foot of the SNCF dyke.
And yet, the hydraulic dynamics of Le Réallon,
which involves quite substantial solids transport,
does not appear suitable for the placement of this
infrastructure. And secondly, because this site’s
exposure to the East does not seem favourable
to an installation of this type, in addition to which
the site is quite confined.
- For reasons relating to the major solids
dynamics, the mouth of Le Boscodon does not
seem relevant.
- Due to the absence of a long-term waterway at
this site, the Les Chappas sector does not seem
appropriate for the development of an artificial
spawning ground either (although a few carexes
were observed at the site during the autumn visit,
the sector does not offer the conditions required
in the study).
In light of these various arguments, the SMADESEP
and the Département Fishing Federation jointly
decided to nix the technical feasibility of the project
at the various sites identified in the 2006 study,
and to continue the prospecting and preliminary
identification of other sites likely to offer the
required characteristics.
D. THE EXPERIMENTAL SITES PROPOSED FOR THE DEVELOPMENT OF
ARTIFICIAL SPAWNING GROUNDS
After a few months of joint investigation, a field
reconnaissance carried out on 1st June 2010
by Michel Delenatte and Frank Gleize enabled
two sites to be identified that would allow the
experiment to be started up under acceptable
conditions. However, the difficulty in gaining access
to these sites (with one only being accessible by
water) meant that new sites had to be looked
for, with priority being given to ease of access to
them. Another site inspection carried out jointly
on 13 October 2011 by Michel Delenatte, David
Doucende and Frank Gleize ultimately enabled the
site located at Riou-Bourdoux to be adopted.
This project, which is of an experimental nature,
is aimed at assessing and then, where applicable,
validating a technique with a view to reproducing
it in the future. Ease of implementation of the
processes and monitoring of the experimental
operation means that easy access to the
sites is required. Furthermore, the technical
characteristics of the geotube product seem
worthwhile implementing under the framework
of this experiment, so that this technique can be
tested at Serre-Ponçon and its adaptability can be
characterised.
51

The development principle would consist of the
implementation of a waterproof geotube 7 enabling
retention of water carried by the streams and/or
thalwegs in the surrounding area. Correlated with
the site’s orientation, the presence of water must
enable the growth of natural vegetation favourable
as a support for the egg-laying of phytophilic
species. In terms of vegetation, carexes (a species
that is native to the area), and various sorts of
reeds and rushes are envisaged.
RIOU-BOURDOUX site
The Riou-Bourdoux creek is capable of hosting
geotube and vegetation planting developments
that will enable the creation of spawning grounds.
The site prospected is located in the borough of
Savines-le-Lac (GPS co-ordinates: N44°31’58’’/
E6°22’02,8’’), on the slope receiving the most
sunlight, with a South-east orientation.
This site, located on the right bank of Riou-
Bourdoux stream, has low input from stormwater.
In light of its exposure, which means it is largely in
the shade, we did note a certain level of humidity
on-site. To this end, the current presence of natural
vegetation can be indicated (and particularly
a patch of land located at an altitude of 775 m
sheltering pondweed covering approximately 4m²),
which tends to persist.
7
Earthworks will have to be envisaged prior to placing the geotube, so that it can lie flat.

The development principle for the site consists
of placing a geotube at an altitude of 776 m NGF,
over a total length of 80 metres, in such a way as
to establish a terrace planted with vegetation that
is approximately 850 m² (25m long running from
upstream to downstream, with the current average
slope being 15% and which it is estimated will be
11% after development).
The geotube will be prefabricated in the factory with
a theoretical diameter of 1.60 m, with an effective
height of approximately 1.00 m once it is filled
out in the field. Placing it and filling it will require
the intervention of a company that has pumping
equipment with an average capacity of 50 to
300 m³/hour approximately. The injection will be
carried out by pumping a mixture of water and sand
into the tubes in accordance with the proportions
recommended by the manufacturer of the geotubes
(approximately 85% water and 15% sand).
After placing the geotube and injecting it,
earthworks will need to be carried out on the bank
with a view to creating a horizontal platform that
is 2.00 m wide, in order to ensure an even height
that is the same right along the route (works
overseen by SMADESEP or a contractor assigned
the backfill work). Care will have to be taken with
the earthworks excavations and backfill so that the
downstream support does not have the structure
on which the geotube will lie undermined, thus
enabling better resistance to wake waves 8 .
Regarding this latter point, due to the nature of the
support soil and the design of the work, it will be
necessary to protect the support soil from erosion in
order to avoid any risk of subsequent undermining
by using a geotextile that prevents this. This
geotextile, made in large panels and laid prior to
the tubes, will have a small ballast system on both
sides, enabling risks of undermining upstream and
downstream from the geotube to be avoided. To do
this, this geotextile that prevents undermining will
have to cover the whole of the support platform,
with an excess of about 1.00 m on both sides.
The copious backfill from the earthworks will then
be laid as a face upstream from the geotube, as
indicated in the preceding diagrams.
The estimated projected timespan for the
earthworks is about one week.
The work involved in planting aquatic plants will
then be carried out by a specialised contractor or inhouse
with the participation of volunteers (who can
be mobilised via the Hautes-Alpes Département
Fishing Federation?).
8
It should be indicated here that the phenomenon of wake waves
is not very important in this creek, but the risk of the geotube
becoming unearthed over a period of a few years should nevertheless
be considered.
53

Scheduling and Timetable
The projected budget for the subsidy request file
refers to an amount of €29,348 for the creation of a
500m² experimental spawning ground.
QUANTITY
UNIT PRICE
IN e EXCL. TAX
TOTAL PROJECTED
PRICE IN e EXCL. TAX
Geotube, 1.6m diam. 80 linear metres € 91 per linear metre € 7,2080
Implementation of the
geotubes
Geotextile to prevent
undermining
Lump sum 14,220 € 14,220
320 m² € 3.60 / m² € 1,152
Backfill sand 135 m 3 € 49.60 / m 3 € 6,696
Reduction for
replacement of the sand
using material taken
from the site
Lump sum - € 1,450 - € 1,450
Total in € (excl. tax) € 29,348
The works implemented relating to the Riou-
Bourdoux site could then be scheduled for autumn/
winter 2011, with a water level enabling the work to
be done under dry conditions. It will be possible to
carry out plantings of vegetation in spring 2012, just
before the lake’s highest water level period, which
is favourable to the growth of suitable vegetation
(the site’s functionality as an egg-laying support
would then only be operational from the following
year onwards).
Experimental site featuring rip-rap with
a waterproof geomembrane (an option
depending on the remaining budget).
In the borough of Chorges (GPS co-ordinates:
N44°29’40’’/E6°18’06’’), on the slope receiving the
most sunlight, with a south orientation.

This site is fed by water from a small stormwater
waterway. Therefore this thalweg could also be
developed into a natural spawning ground by
laying a tube consisting of a waterproof geotextile
and a rip-rap (laying a geotube seems to be more
difficult here, in light of the height of the device to
be set in place which, ideally, must be wedged in
position at 776.5m NGF).
The development principle consists of the
placement of a rip-rap that is 12m wide, with a
maximum height of 1.50m in order to level a fairly
substantial spawning terrace. The implementation
of a waterproof geomembrane is then aimed at
maintaining an acceptable humidity level on this
terrace, which has stormwater running through
it. The presence of green waste dumped just
upstream, which is likely to provide organic
material due to breakdown and then leaching
during rainstorms, should be noted.
The total space requirement for this experimental
spawning ground should reach approximately
120-150m² (20m long running from upstream to
downstream, with a slope of 7%).
Semi-waterproof
geotextile membrane
QUANTITY
UNIT PRICE
IN e EXCL. TAX
TOTAL PROJECTED
PRICE IN e EXCL. TAX
35 m² € 19.30 / m² € 675.50
100/400 kg blocks 12 m 3 € 82.20 / m 3 € 986.40
Implementation Lump sum € 2,702 € 2,702
Total in € (excl. tax) € 4,363.90
E. BIBLIOGRAPHIC REFERENCES USED FOR THIS EXPERIMENT
BETEREM & PM Consultants, 1999. Schéma
d’Aménagement et de Développement des Berges
de Serre-Ponçon. Site management: SMADESEP.
CEMAGREF, 1992. Réhabilitation des abords de
Serre-Ponçon.
CHAPPAZ R., 2008. Étude hydrobiologique de
le retenue de Serre-Ponçon, Université d’Aix-
Marseille. Site management: SMADESEP.
Guide méthodologique des Agences de l’Eau,
1999. Protection et végétalisation des zones de
marnage des plans d’eau. Guide No. 66.
RUHL C., 2004. Développement des supports
de pontes de brochets à Serre-Ponçon. Site
management: Fédération Départementale de
Pêche 05.
SOGREAH Consultants, 2005. Étude du
phénomène d’exhaussement en queue de retenue
de Serre-Ponçon et mesures compensatoires. Site
management: SMADESEP.
SOGREAH Consultants, 2005. Proposition
d’actions contre les vents de sables. Site
management: SMADESEP.
55

3. LAKE OSSIACH (a):
Creation of a huge wetlands zone on the lake’s edge,
providing spawning grounds
LAKE OSSIACH (A)
Context
Tools
implemented
Author -
silmas
contact
• Major regression in the 1970s-80s of macrophytes’ aquatic plant habitats to the
advantage of phytoplankton
• Negative impacts on the quality of the fish habitats and spawning grounds
• Restoration of the quality of the water and sediments, with a view to facilitating the
development of macrophytes
• Project for the creation of a huge wetlands zone on the lake’s edge, providing
spawning grounds
Carinthia (Kärtner) Region, Environment Department
roswitha.fresner@ktn.gv.at ; www.ktn.gv.at/27987_DE
A. GENERAL DESCRIPTION OF LAKE OSSIACH
With 10.79 km², Lake Ossiach is the third
largest lake in Carinthia. It has always been a
highly esteemed tourist destination. The natural
environment and pleasant water temperatures,
which can reach up to 27°C, provide an ongoing
attraction for swimmers at the 6 existing beaches.
Nestled in-between wooded slopes. The name
Ossiach comes from the Slavic word osoje, which
means “shadow”. Lake Ossiach is located inbetween
the wooded precipices of Gerlitzen to the
north, and the western foot of the Ossiacher Tauern
to the south. The lake’s basin lies in the midst of a
rocky massif which is partially covered by glacial
gravel. Two basins, separated by a sill at a depth of
10 m, characterise this lake. To the east is the small
basin (3.9 km²) with a depth of 11 m, and to the
west is the large basin (6.9 km²) with depth of over
52 m. Given that a great part of the lake is shallow,
its average depth is only 19.6 m, which is relatively
small compared to its size.
Water from the Gerlitzen region flows into
the lake via several different influents. Of these
numerous influents, the Tiebel River is the one with
the greatest flow rate, with 1,750 litres per second.
To the east of the lake is the Bleistätt marsh, which
is crossed by the Tiebel, and has a surface area
of approximately 6 km². In the 1930s, the marsh
was drained using drainage ditches. Since then,

this surface area has been used for intensive
agriculture. Water rich in nutrients is discharged by
pumping it into the Tiebel and, subsequently, into
Lake Ossiach. The lakewater is discharged via the
Seebach outlet, with an average annual flow rate
of 3,320 l/s.
Swimming water of impeccable quality.
Lake Ossiach is classified as a type with a low
mesotrophic level, with a slightly high nutrients
rate, but which has a water quality that is ideal
for swimming. Lake Ossiach is holomictic, which
means that it is mixed during circulation periods in
spring and autumn. In summer, at surface level the
water is heated to temperatures exceeding 24°C.
The water body is stratified from May to November.
The ice coverage only lasts a few weeks. But during
mild winters, Lake Ossiach is not covered in ice.
Lake Ossiach’s limnological development has been
under observation since 1931.
Lake Ossiach’s banks that are still in their
natural state have been classified as nature and
landscape conservation zones. These seven
protected zones constitute a surface area of
370 hectares.
NSG Tiebelmündung: 30.5 ha, LGBl. Nr. 30/1959,
19/1960, 16/1968
NSG Jammernspitz: 5.1 ha, LGBl. Nr. 31/1959,
19/1960
NSG Meerspitz: 8 ha, LGBl. Nr. 65/1957
NSG Ossiacher See – Westbucht: 8 ha, LGBl.
Nr. 15/1964
LSG Ossiacher See – Ost: 284 ha, LGBl.
Nr. 26/1970
LSG Ossiacher See – Westbucht: 20 ha, LGBl.
Nr. 37/1970
LSG Bodensdorf: 10 ha, LGBl. Nr. 25/1970
A holiday destination that is very popular
with tourists. Already in the first half of the 19th
century, Lake Ossiach was appreciated as a
summer destination. Today, numerous hotels and
restaurants along the edge of the lake offer all
sorts of leisure pursuits and activities. The Ossiach
Convent on the south bank is particularly wellknown
for the numerous events held there. In the
lake’s vicinity, tourism has developed rapidly. The
number of nights spent there went from 100,000
in the early 1950s to 2 million in the 1980s back
to 1 million nowadays. Annenheim, Sattendorf,
Bodensdorf, Steindorf and Ossiach are the main
destinations on the lakeshore, and the largest town,
Feldkirchen, has approximately 7,800 inhabitants.
A bicycle tour around the lake. You can do a tour
around the lake on a bicycle. The cycle path goes
via the end of the lake in the western part on the
Ossiacher Seebach (Lake Ossiach’s runoff zone).
Due to its great richness in terms of ichthyofauna,
vegetation and populations of waterbirds, a
6.6-hectare wetland zone offers shelters, safety
and food. Near the town of Feldkirchen, east of the
lake, there is a small aerodrome (ICAO-Kennung:
LOKF; Tel.: +43 (0) 4276 2707) for gliders. From
early May to late October, two transport boats
travel regularly between nine ports.
B. FISH POPULATION
According to studies conducted from 1994 to 1997
(Farkas & Olsacher, 1998), Lake Ossiach has the
following fish species:
species LATIN name species LATIN name
Lake trout Salmo trutta Bleak Alburnus alburnus
Rainbow trout Oncorhynchus mykiss Silver bream Blicca bjoerkna
Pumpkinseed Lepomis gibbosus Common bream Abramis brama
Whitefish Coregonus lavaretus Carp Cyprinus carpio
Pike Esox lucuis European catfish Silurus glanis
Roach Rutilus rutilus Eel Anguilla anguilla
Crucian carp Carassius carassius Pikeperch Sander lucioperca
Chub Leuciscus cephalus Vimba bream Vimba vimba
Rudd Scardinius erythrophthalmus Barbel Barbus barbus
Tench Tinca tinca Burbot Lota lota
57

A decline in richness in terms of fish species.
Since observations carried out by Findenegg in
1934, no further species have been demonstrated.
The fish populations in the lake are quite low,
and certain species even seem to be extinct
there. The disappearance of the populations of
bitterlings (Rhodeus sericeus) is probably closely
linked to the decline in bivalves. The European
catfish (Siluris glanis) population, which was once
high, has declined sharply, doubtless due to the
eutrophication of Lake Ossiach. Before, remarkable
large specimens of European catfish (Siluris glanis)
were caught - for example in 1946 - with one
specimen, that was 230 cm long, weighing 65kg.
Findenegg (1934) also indicated the presence of
the ide fish (Leuciscus idus). He mainly relied on
information from the biologist Haempel. These
individuals were probably chubs (Leuciscus
cephalus).
The main species of fish in the lake is bream
(Abramis brama), which constitutes about 30%
of the fish population. During an electric fishing
operation carried out during the reproduction
period, approximately 10 tonnes of fish belonging
to this species were caught. The stock of roaches
(Rutilus rutilus) in Lake Ossiach seems to be
declining; what is found there are primarily large
specimens, whereas the number of young roaches
is low. Consequently, the number of catches of
pikes (Esox lucius) is falling dramatically, due to
the change in the macrophytes habitat, which
provides both a support for the eggs during
spawning, and a feeding zone as well.
Following the failure of restocking with whitefish
(Coregonus lavaretus) during the 19th century,
a new attempt at introducing them was carried
out in 1982. After a period of time, a population
was established. With an abundance rate of
approximately 10%, whitefish constitutes the
third largest population in the lake, after bream
and roach. The stock of Salmonidae – rainbow
trout (Oncorhynchus mykiss) and lake trout
(Salmo trutta) - in Lake Ossiach is relatively low.
The reason for this is the relatively high summer
temperatures and the lack of appropriate
spawning grounds.
Even though there is no natural reproduction
of carps (Cyprinus carpio), regular stocking
operations guarantee the future of sports
fishing. The stock of bleak (Alburnus alburnus)
has declined sharply. The bleak once constituted
the European catfish’s main food. Hartmann
(1898) reported that during the spawning
period, large quantities of bleak were caught
and used as a source of food, along with potatoes
and polenta. The main reason for this sharp
drop in populations of bleak is the presence of
the zebra mussel (Dreissena polymorpha) in the
spawning zones (Farkas & Olsacher, 1998).
Lake Ossiach’s annual yield is currently
approximately 20 kg/ha.
Shallow water biotopes as spawning grounds.
In early 2000, a shallow water habitat was created
about 5 hectares from Lake Ossiach’s outlet. Initial
studies showed that the habitat is mainly used

as a spawning zone and as a habitat for roach,
rudd, perch, bleak, pike and European catfish.
Shortly after the zone is flooded in spring, you can
already observe bleak and pike there. This shallow
water zone has a positive effect on the overall fish
population in Lake Ossiach.
Leisure fishing. The lake is divided into more than
30 fishing zones.
The presence of shellfish. During the last few
years, on several occasions, divers have observed
the European crayfish (Astacus astacus). They
probably migrated via small influents from ponds
in the Ossiacher Tauern, where they reproduce
frequently. During the last few years, the European
crayfish has also been observed in the top end
of the Seebach. It was in Lake Ossiach, in 1880,
that the crayfish plague appeared for the first
time in Carinthia (Hawlitschek, 1892). Before the
appearance of this pest, nearly all the lakes in
Carinthia were densely populated by indigenous
crayfish. This plague caused by the fungi
(Aphanomyces astaci) has cropped up in Carinthia
at the end of the 19th century in several waves and
has caused an immense damage. These waves but
also the stocking of eel, a not native species, have
prevented a denser population of crayfish in most
of the larger lakes in Carinthia.
C. THE REVITALISATION PROJECT “BLEISTÄTTER MOOR”
Algae floating on the surface of Lake Ossiach.
On sunny days parts of the lake can be covered
with patches of brown scum built by the blue
algae Ocillatoria princeps. These algae growth
on lake sediments that is rich in nutrient. On
hot, sunny days, the algae can produce so
much gas that conglomerates of the algae
take off from the sediment and slide to the
surface. These algae, which are mainly found in
shallow waters up to a depth of 8 m, develop
mainly in the eastern basin of lake Ossiache See.
Causes. The proliferation of algae is directly
related to the disappearance of macrophytes in the
1970s. Indeed, in shallow waters, the lack of shade
enables the light to penetrate right to the bottom,
thus facilitating their growth.
Measures. In order to combat this proliferation of
algae, the Land of Carinthia drew up a restoration
project consisting of three modules.
a. Module 1
The removal of sediments in the estuary area of the
river Tiebel was finished in 2008. By this measure
the water running into the lake can pass through
the deeper part of the lake.
Action plan
- August to December 2005: Exploration of the
substrate of the Tiebel River delta;
- February to August 2006: Geotechnical
assessment;
- September 2006 to May 2007: Construction of
the sill/dam (Teuffenbach earthworks);
- September to December 2006: Suction dredging;
- Up to September 2007: Remaining works.
Estimated costs: €1,110,000
Real costs: Approximately €850,000
59

. Module 2
An area currently occupied by intensive
crops, is going to be flooded in order to create
a basin that will enable water to be recovered
from the Tiebel before it is discharged into the
lake. The floodable area (the basin) will function
as a buffer zone in which suspended solids
and nutrients will be held. The project dossier
were prepared for the permission requests
procedure responding to the water and nature
protection acts and submitted to the responsible
government agency.
Action plan
- Underground exploration of the substrate from
August to December 2005;
- Geotechnical assessment from February to
August 2006;
- Adaptation of the containment dam from April to
June 2008;
- Adaptation of the Steindorf flood protection dyke
from April to June 2008;
- Submission of project dossier for permission
procedure in July 2011;
- Implementation of measures, including the
construction of the water pumping station for the
Bleistätter Moor co-operatives from 2011 to 2012,
with the remaining work being done in 2013.
Estimated costs: €1,995,000
Real costs: Approximately €250,000
c. Module 3
Dredging of Sediments in the eastern bay of Lake
Ossiacher See was done during the winters along
3 years. In total a surface area of 24 ha to a
maximum depth of 7 m was treated. An amount
of 217,000 m³ of lake sediment got removed
between 2007 and 2009 from the lake. The
sludge was dredged because the consistent
and structure of sediment was improper for the
development of macrophytes.
Estimated costs, including land purchases:
€4,186,000
Costs to date: €1,650,000
Expected costs: €200,000
A boat is adapted for gathering up the surface
algae which is working during summer and is at
the moment the only way to minimize the impact
of these benthic algae on leisure activities
(swimming, boating etc.).
But this measure is only cosmetic and cannot
help to solve the problem. Nevertheless it works
well and removes the algae patches from the
surface. The measures of the whole restoration
project are aimed to improve the ecosystem of
the eastern bay and furthermore of Lake
Ossiacher See sustainable.
D. RESEARCH EFFORTS AND PRELIMINARY STUDIES ON THE ECOLOGICAL
STATUS OF THE LAKE AND THE CATCHMENT AREA
Action plan
- Nutrient load coming from the Bleistätter Moor;
1978
- Survey on causes for the massive appearance of
benthic algae Oscillatoria princeps; 2000
- Development of phytoplankton in Lake Ossiacher
See; 2008
- Survey on current status of lake shore
constructions; 2009
- Long-term limnological development of Lake
Ossiacher See; 1964-2005
- Mapping of macrophytes and evaluation
according to WFD; 2009

E. PARALLEL RESEARCH EFFORTS
CARRIED OUT
Action plan
- Planting and monitoring of the development of
the aquatic plants;
- Evaluation of the ecological status of Lake
Ossiach in relation to the development of aquatic
plants;
- The SILMAS project.
F. THE PROJECT’S STATE OF PROGRESS IN 2011
The Province Carinthia owns already 93 ha of
the 100 ha of land required for setting up the
basin (floating zone). This area is no longer used
for agricultural purposes. The support study
concerning the macrophytes showed that their
development is clearly influenced by the state of the
sediments in terms of both quality and structure.
The study demonstrated that the high phosphorus
concentration (approximately 1,243 mg/kg of dry
solids) is one of the major obstacles preventing the
development of macrophytes. The high quantity
of suspended solids transported by the Tiebel
River into Lake Ossiach also has an influence on
their development.
Photomontage – View of the floodable zone
during low water periods
Indeed, these suspended solids are deposited
on aquatic plants and prevent them from carrying
out photosynthesis.
Sucking up the sediments in the delta has altered
the water circulation arriving from the Tiebel River,
providing a slight improvement in terms of the
quality of the sediments.
A clear improvement in the quality of the
sediments and, consequently, an improvement in
the development of macrophytes, will mainly be
perceptible once the basin has been established
(floodable zone).
61

© M. REGNIER / SILA
V. The lessons from the
experiments
conducted within
the partnership, and
transposing them

The various situations referred to above relate to a
quite particular context: the quality of the lake and
of its fish stocks, the type and importance of the
fisheries exploitation, governance, etc. Attempting
to transpose a successfully concluded approach
applied to lake X exactly the same way at lake
Y would in no way guarantee absolute success,
because the local particularities and the history of
each site absolutely must be analysed beforehand
and integrated.
However, each of the experiments encountered
within the SILMAS partnership provides general
lessons regarding resolving an issue or a
management problem. Based on the feedback
from the 8 cases presented, it is possible to
highlight common elements, which are certainly
a matter of good sense, but which in practice are
either applied to a greater or lesser extent, or are
sometimes simply left out by managers.
The limited number of feedback cases taken
into account means that this analysis is
not of an exhaustive nature in terms of the
diversity of existing situations and actions to
be carried out. However, thanks to the different
themes covered by the experiments conducted
by the SILMAS partners, it is possible to find a
certain number of general principles required for
sustainable management of fisheries resources in
a lake environment.
1. The importance of knowledge of
the fish stocks
The data of the catches made by fishermen is not
sufficient to get a real picture of the abundance
and specific diversity of the fish stock. Due to
the balances and close ecological links that exist
between and within each population (inter- and
intraspecific relations), it is important for knowledge
not to be limited to 2 or 3 main species sought after
as a matter of priority by fishermen.
Scientific sampling operations using mesh nets,
electric fishing, and hydroacoustic campaigns, are
thus conducted on most lakes (Lake Constance,
Annecy, Bourget, Idro, Serre-Ponçon, Ossiach),
and enable updating of the data concerning the
ichthyofauna: specific diversity, including the
appearance of non-indigenous and/or invasive
species, abundance, etc. These sampling
operations can also provide an opportunity for
analysing the public health quality of the fish
(Bourget, Annecy) with regard to quality standards
in terms of contamination by micropollutants.
These specific studies of the ichthyofauna,
which are often carried out on a five-year basis,
may, depending on the country in question,
be supplemented by data obtained under the
framework of water bodies monitoring networks
required by the Water Framework Directive,
the “fish” section of which constitutes a part of
assessing the good ecological status.
2. Taking into account the quality of
the lake and its monitoring
Without going into any further detail - the reader
may refer to the abundant literature devoted to
limnology – it is clear that an understanding and
management of the fish stocks requires sound
knowledge of the state of the environment in
which they exist.
The physical and chemical quality of the water and
sediments, the physical quality of the habitats (the
lake bottom, the lake littoral, the connectivity to
the influents, etc.), and biological compartments
(phytoplankton, zooplankton, benthic invertebrates,
and macrophytes) are studied regularly in the case
of most of the lakes presented (Lake Constance,
Annecy, Bourget, Iseo, Serre-Ponçon, and
Ossiach), with a history of this going back to the
mid-20th century in the case of some of them.
The data acquired enable the functionalities of
the various stages in the life cycles of the fishes
63

Measurement of the main physicochemical parameters of the water column using
a multi-parameter probe (Photo : D. ZANELLA / SILA)
to be evaluated (hatching and development of the
juveniles, growth, reproduction, etc.), as well as
evaluation of the general productivity of the lake,
mainly using the content levels of nutrients such
as phosphorus and nitrogen. Bear in mind that
sustainable fisheries exploitation is only possible
if catches do not exceed what the environment
is capable of producing naturally, whilst at the
same time guaranteeing the long-term viability and
replenishment of stocks.
A few lakes are committed to “Lake Contract”
type procedures, which enable a comprehensive
overview of the whole lake ecosystem and, more
broadly speaking, of its catchment area (Iseo,
Bourget, Annecy). Diagnostics of environmental
issues are thereby facilitated, as is defining the
most relevant actions to be implemented, with a
view to ensuring their complementary nature and
their effectiveness.
Certain lakes are still subject to major intakes of
nutrients, leading to processes of eutrophication.
Other lakes, for which water quality preservation
and restoration actions have been implemented,
are experiencing a reverse process of
reoligotrophication (Lake Constance, Annecy,
and Bourget). In both cases, we can observe
developments in terms of productivity, growth
and the reproduction of the fish species, which
should be properly understood in order to adapt
the fisheries regulations if need be: quotas, legal
catch size, etc.
3. Monitoring fisheries activities and
the evaluation of management
practices
Regardless of the type of fishing exploitation
(leisure, professional), monitoring of fisheries
activities is undertaken on most lakes: the number
of fishermen, catch books, field surveys, etc. The
collection and then analysis of these data by the
structure responsible for monitoring generally gives
rise to the publication of an annual report.
In addition to the most straightforward pieces
of information – the quantity of fish caught, and
possibly the number – that the practitioners
must often fill in on a mandatory basis, it may
be worthwhile to request volunteer fishermen
in order to gather more detailed data, thus
providing precious information for management

purposes (Annecy, Bourget): the number of
trips and their duration, the number and size of
catches under and over the legal size, the sectors
prospected, and possibly the collection of scales
or identification of markets, etc. In order to be able
to acquire and exploit these data on a long-term
basis, this type of operation does however require
that the volunteer fishermen be kept informed and
they must be subject to ongoing co-ordination.
Sometimes, it is necessary to gain more in-depth
knowledge of the exploitation of the species,
as well as of their biology, in order to deal with a
particular management issue. Specific studies
may thus be undertaken such as, for example, on
Lake Annecy, where full monitoring of whitefish
fishing (the size and weights of catches, growth
measurement using scale-reading, age and sexual
maturity, etc.) was carried out over three years in
order to update regulations and management.
Supporting fish populations by releasing
young fish is a widespread practice at alpine
lakes. However, the success of these operations
varies greatly and depends on numerous factors.
Evaluating their effectiveness, for example
by returns of marked fish caught by fishermen
(ablation of a fin, plastic marker, fluorescence
marking of the otolites) requires a major, prolonged
effort over several years, but does make it possible
to substantially improve practices (Bourget). The
catching of spawners in the natural environment,
which is sometimes necessary in order to obtain fry,
may provide an opportunity for acquiring biometric
data concerning a large number of individuals,
returning markers, etc.
Whether it is imposed by national regulations
or on the initiative of the managers, drawing up
a fishing management plan is a generalised
practice at most of the lakes. Based on diagnostics
of the situation, this tool makes it possible to set
the objectives to be achieved whilst at the same
time defining the management parameters: general
regulations, the fishing periods, fishing reserves, a
support programme for the various populations by
releasing young fish, protection and restoration of
spawning grounds zones, etc.
Lastly, although it was not referred to in the feedback,
controlling compliance with the regulations
out in the field (fishing police), should also be
mentioned due to its role not only in cracking
down on infringements, but also in prevention and
providing fishermen with information. Although
it is sometimes limited due to a lack of financial
resources, a regular presence out in the field
is however a key factor for ensuring compliance
with the rules established. It also makes it
possible to provide important information for the
assessment of management practices: measuring
the satisfaction of the fishermen, gathering
eyewitness accounts, and also ensuring the
reliability of the details entered in catch books (the
summaries of which frequently orient or validate
management measures).
4. The implementation of habitats
restoration actions
Although they have received less media coverage
than issues relating to water quality, the
deterioration of the physical habitats in alpine
lakes and their influents may however have major
consequences for fish populations. There are
various causes of this: control of the lake level (too
great an amplitude/variations etc. or not enough),
deterioration of the littoral habitats, hydraulic
obstacles on influents that disrupt the migration of
species, etc.
The lakes in the SILMAS programme bring together
several interesting experiments in terms of the
restoration of physical environments, involving
the submersion of wooden structures (Iseo,
Constance), the creation of spawning grounds by
flooding wetlands on the lake’s edge (Ossiach) or
by creating mini containment works in the case of
a dammed lake with high variations in water levels
(Serre-Ponçon). Other actions not detailed in this
document are aimed at restoring aquatic reed beds
(Constance, Annecy, Bourget).
In all cases, these projects are built on the basis
of full diagnostics of the situation that incorporate
all of the physical and biological components of
the environment, as well as seeking out similar
feedback. Post-works studies then make it
possible to evaluate their effectiveness: animal and
plant colonisation, long-term conservation, etc.
65

5. Local governance that
is indispensable
From the smallest to the largest of the eight
lakes taken into account in this feedback, all
of them have a body which brings together not
only fisheries actors, but also representatives of
all the stakeholders involved in management of
the lake. Whether they are called the “International
Fishing Commission”, the “Consultative
Committee”, or the “Steering Committee”, these
tools enable comparison of the various points
of view, and make it possible to inform people,
debate the orientations to adopt in the field
of management, and to resolve any conflicts
with other users of the lake.
Generally, a plenary meeting enables an assessment
of the past year to be drawn up, presentation
of knowledge acquired, and any wishes of the
stakeholders, in order to change management
practices or the regulations if necessary. Ideally,
the latter must be able to be changed easily and
regularly (Lake Constance, Annecy, Bourget,
Idro, Bohinj), depending on changes in the
various parameters. Working groups can also be
organised in order to deal with particular tropics
upstream, in limited committee meetings.
Scientific support is generally associated with
it, in the form of a group of experts (Constance)
or a Fisheries Scientific Committee (Annecy).
The proximity of a university or a research
laboratory specialising in the theme facilitates
making these skills available.
Assessments may be useful for resolving specific
problems. In the event of regular blockages
or unsolvable conflicts, sometimes you need to
call on specialists who are from outside the
local context, and who provide a new, independent
view of the situation (Annecy), or who enable
changes to be made to old practices considered
to be fixed benefits, but for which change is
fundamental (Idro).

VI. Summary sheets
relating to each lake
© R. MASSON
67

Summary sheets relating to each lake
- Annecy (F).................................................................................................................. 69
- Bourget (F)................................................................................................................. 70
- Serre-Ponçon (F)........................................................................................................ 71
- Constance (D-A-CH).................................................................................................. 72
- Ossiach (A)................................................................................................................. 73
- Wörthersee (A)........................................................................................................... 74
- Idro (I)......................................................................................................................... 75
- Iséo (I)........................................................................................................................ 76
- Candia (I).................................................................................................................... 77
- Avigliana Grande (I).................................................................................................... 78
- Caldonazzo (I)............................................................................................................ 79
- Ledro (I)...................................................................................................................... 80
- Garda (I)..................................................................................................................... 81
- Levico (I)..................................................................................................................... 82
- Terlago (I).................................................................................................................... 83
- Bohinj (SLO)............................................................................................................... 84
Summary of the action................................................................................................. 85

LAKE ANNECY
France
Characteristics
LAKE
catchment area
Surface 27 km 2 Surface 270 km 2
Length 14.6 km Average altitude 900 m
Width 3.2 km Maximal altitude 2,351 m
Altitude 447 m Population ~ 130,000 hts
Average depth 41 m
- L’Eau Morte
Maximal depth 65 m
Main tributaries
- L’Ire
- Le Laudon
- La Bornette
Water change time 3.8 years Emissary of the lake - Le Thiou
Organization of the fishing activities
Lake owner: French State
Fishing right owner: Frenche State - rent of the fishing right to leisure fishermen + 3 professional fishing licences
Regulation: National law + specific regulation for the Lake Annecy
(http://www.haute-savoie.equipement-agriculture.gouv.fr/peche-r150412.html)
Institution in charge of the fishery: Direction Départementale des Territoires (DDT)+Committee gathering all stakeholders
Main species: Whitefish, arctic char, lake trout, pike, perch, roach, burbot… total of 19 species
Leisure fishing : Yes Organization: One association; ~ 1000 boat fishermen
Professional fishing : Yes Organization: 2 pro. fishermen, gathered in an «interlakes» association
(+Bourget and Geneva)
Fishing monitoring and studies
Institution: DDT+ SILA + INRA + ONEMA
Regular monitoring: Yes, fishing statistics (obligatory fishing book for leisure and pro. fishermen)
Specific studies: Yes, expertise (2007, 2010), scientific sampling EN 14757 (2007, 2010), acquisition of recent data
on the fishery exploitation (2008 to 2010), voluntary fishing book (since 1987), effectiveness of the arctic
char stocking
State of the fish communities
Functionality: No particular problem. Trend of reduction of the whitefish growth (oligotrophication of the lake)
Stocks: Not precisely known, but trend to lower catches of whitefish and arctic char
Sanitary quality: Forbidden to consume/to sell arctic char over 40 cm (PCB)
Pressures on the fish communities
Overexploitation: High pressure due to leisure and pro. fishing - adjustments of regulation in 2011
Eutrophication: No, on the opposite strong oligotrophication
Deterioration of the physical habitat: Important decrease of the surface of reed beds (1950-1980) ; however tributaries
in good ecological state and good circulation of the migratory fish from the Lake
Invasive species: Yes (crayfish, zebra mussel, Corbicula sp.,…), but unknown real ecological impact
Management tools and specific practices
Restoration actions: Lake water quality, lakeshore restoration (reed beds), arctic char spawning grounds restoration and
prohibition of diving on the spawning grounds during winter
Fishing management: Arctic char and lake trout stocking
Conflicts uses regarding fishing: Recurrent conflict between leisure and pro. fishermen ; more recent conflict between leisure
fishermen and sport activities that produce waves (ex. wakesurf)
SILMAS Partner - contact for further information
Syndicat Mixte du Lac d’Annecy (SILA)
7 rue des Terrasses,
74960 Cran-Gevrier - FRANCE
www.sila.fr
sila@sila.fr
69

Lake Bourget
France
Characteristics
LAKE
catchment area
Surface 44.5 km 2 Surface 588 km 2
Length 18 km Average altitude 500 m
Width 3 km Maximal altitude 1,845 m
Altitude 231.2 m Population ~ 180,000 hts
Average depth 81 m
Main tributaries
- La Leysse
Maximal depth 145 m
- Le Sierroz
Water change time 7 years Emissary of the lake
- Canal de
Savières
Organization of the fishing activities
Lake owner: French State
Fishing right owner: French State
Regulation: National law + specific regulation for the Lake Bourget
(http://www.savoiepeche.com/storage/fichiers/arp_bourget_2011.pdf)
Institution in charge of the fishery: Direction Départementale des Territoires + Committee gathering all stakeholders
Main species: Whitefish, lake trout, arctic char, perch, pike, roach, pikeperch, burbot…. total of 22 species
Leisure fishing : Yes Organization: 2 associations (~1500 boat fishermen) +
1 association of leisure fishermen using nets and other tools (42 fishermen)
Professional fishing : Yes Organization: 10 fishermen, gathered in an «interlakes» association
(+ Annecy and Geneva)
Fishing monitoring and studies
Institution: DDT + CISALB (1 «fishery coordinator» job since 2003)
Regular monitoring: Fishing statistics (fishing book for leisure and pro. fishermen)
Specific studies: Scientific sampling with gillnets + hydroacoustic studies (autumn, spring) in 2004-2005
State of the fish communities
Functionality: Whitefish: improvement of the reproduction since the restoration of the lake water quality. Arctic char: problem
of functionality between the stage «egg» and the stage «larva». Lake trout: problem of reproduction due to the
quality of the tributaries and their connectivity to the lake
Stocks: Increase of the whitefish population
Sanitary quality: Regulation measures due to the presence of PCB to consummate/sell arctic char, eel, roach>10cm,
bream and tench
Pressures on the fish communities
Overexploitation: High level of exploitation for whitefish and perch - monitored
Eutrophication: No, at the opposite in step of re-oligotrophication (improvement of the whitefish reproduction)
Deterioration of the physical habitat: Problem of deterioration of the tributaries’ quality for the lake trout reproduction
Invasive species: Cyclic problem of proliferation of catfish, but unknown impact. Pacific crayfish (Pacifastacus leniusculus),
non-threatening but necessity to be vigilant
Management tools and specific practices
Restoration actions: Improvement of the lake water quality, restoration program for the lake trout (tributaries)
Fishing management: Stocking for whitefish and arctic char since 1980 («pacage lacustre»)
Conflicts uses regarding fishing: Existence of a structure of exchange between amateur and professional fishermen,
but regular conflicts about the rights and tools attributed to each category of fishermen
SILMAS Partner - contact for further information
CISALB
42 rue Pré Demaison
73000 Chambéry - France
www.cisalb.com
info@cisalb.fr

LAke SERRE-PONÇON
France
Characteristics
LAKE
catchment area
Surface 28.9 km 2 Surface 3,580 km 2
Length 20 km Average altitude 2,130 m
Width 2 km Maximal altitude 2,505 m
Altitude 780 m Population ~ --- hts
Average depth 25 m
Main tributaries
- La Durance
Maximal depth 110 m
- L’Ubaye
Water change time 0.5 year Emissary of the lake - La Durance
Organization of the fishing activities
Lake owner: French state
Fishing right owner: French state - rent of the fishing right to leisure fishermen (association and departmental Federation)
Regulation: National law + specific local regulation between the different departments that share the lake
Institution in charge of the fishery: Direction Départementale des Territoires + local stakeholders
(public administrations, departmental fishing Federation…)
Main species: Lake trout, arctic char, whitefish, pike, perch, bleak, roach…
12 allochthonous species, 3 autochthonous species
Leisure fishing : Yes Organization: One local association + involvement of the departmental Federation
Professional fishing : No
Fishing monitoring and studies
Institution: DDT+ SMADESEP, local fishing association and department Federation
Regular monitoring: Yes, catches book for leisure fishermen using specific tools (winches, spinnaker)
Specific studies: Scientific samping using gillnets each 5 years
(quantity, diversity, evolution of the species)
State of the fish communities
Functionality: Artificial lake and modification of water level (marling): strong difficulties for the reproduction of some fish, and
for the growth of youngs-of-the-year of the majority of the species (no riparian vegetation)
Stocks: Increase of the natural reproduction of whitefish. Necessity of stocking for lake trout, arctic char and pike
Sanitary quality: Good
Pressures on the fish communities
Overexploitation: No, low level of fishing pressure
Eutrophication: Yes, cyprinids dominate the fish communities
Deterioration of the physical habitat: Hydraulic management of the lake: perturbation of the shore habitats
Invasive species: American crayfish and zebra mussel since recent years
Management tools and specific practices
Restoration actions: Pilot project in development to vegetalise the shore of the lake
Fishing management: Stocking of lake trout, arctic char and pike
Conflicts uses regarding fishing: No
SILMAS Partner - contact for further information
Syndicat Mixte d’Aménagement et de Développement de Serre-Ponçon (SMADESEP)
Rue de Morgon,
05160 Savines Le Lac - FRANCE
www.smadesep.fr
info@serre-poncon.com
71

Lake CONSTANCE
Germany, Austria, Switzerland
Characteristics
LAKE
catchment area
Surface 535 km 2 Surface 11,487 km 2
Length 63 km Average altitude --- m
Width 13 km Maximal altitude --- m
Altitude 395 m Population ~ 1,200,000 hts
Average depth 90 m
Main tributaries
- Rhin
Maximal depth 254 m
- Bregenzerach
Water change time 4.5 years Emissary of the lake - Rhin
Organization of the fishing activities
Lake owner: Germany, Austria, Switzerland
Fishing right owner: Bordering Länders, Cantons, and also Austria State
Regulation: Common regulation transposed into the laws of the three States of the lake
Institution in charge of the fishery: International coordination structure (IBKF, www.ibkf.org)
Main species: Whitefish, perch, pike, arctic char, lake trout, ruffe… total of 29 species
Leisure fishing : Yes Organization: ~ 13 000 fishermen for the overall lake
Professional fishing : Yes Organization: ~ 150 fishermen
Fishing monitoring and studies
Institution: IBKF, University of Constance, Fisheries Agency of Baden-Württemberg
Regular monitoring: Yes, fishing statistics since 1914, fisheries investigations by the fishing guards, mainly for whitefish and
perch
Specific studies: Scientific sampling monthly by gill nets
State of the fish communities
Functionality: Return of an oligotrophic lake quality: improvement of the success of the reproduction for all species
Stocks: Return to a situation prior to the period of eutrophication. Whitefish represents 75 to 80% of captures, but the overall
tonnage and size of the catches are declining. Arctic char is increasing, partly due to better breeding conditions, even
if the impact of the stocking is not known precisely
Sanitary quality: ---
Pressures on the fish communities
Overexploitation: Important and monitored for whitefish and perch
Eutrophication: No, at the opposite return to an oligotrophic quality
Deterioration of the physical habitat: Shoreline (reed beds), connectivity between the lake and its tributaries
Invasive species: High population of ruffe. Discovery in 2006 of an invasive freshwater shrimp
(Limnomysis Beneden), population is increasing but unknown impact
Management tools and specific practices
Restoration actions: Shoreline restoration, actions of improvement of the connectivity with the tributaries
Fishing management: Stocking for lake trout, arctic char, and whitefish
Conflicts uses regarding fishing: Reoligotrophication of the lake is one of the causes of the decline of the catches of perch
(but has permit in the same time to recover the whitefish fishery)
SILMAS Partner - contact for further information
Institute for Lake Research Baden-Württemberg LUBW
Argenweg 50/1
88085 Langernargen - Germany www.lubw.baden-wuerttemberg.de

LAke ossiach
Austria
Characteristics
LAKE
catchment area
Surface 10.8 km 2 Surface 162.9 km 2
Length 10.4 km Average altitude 600 m
Width 1.5 km Maximal altitude 1900 m
Altitude 501 m Population 25,121 hts
Average depth 19.9 m
Maximal depth 52.6 m
Main tributaries - Tiebel
Water change time 1.8 year Emissary of the lake - Seebach
Organization of the fishing activities
Lake owner: Österreichische Bundesforste AG
Fishing right owner: Alliance fishery
Regulation: Regional laws
Institution in charge of the fishery: Regional authority
Main species: Bream, whitefish, roach, chub, rudd, tanch, perch, silver bream, pike, carp, bleak, eel… total of 22 species
Leisure fishing : Yes Organization: 2 leisure fishing associations
(www.sportfischerei-villach.at and www.aesche.at)
Professional fishing : No
Fishing monitoring and studies
Institution: Regional authority, Lake research institute of Carinthie
Regular monitoring: Questionnaires to fishermen and fishing statistics
Specific studies: Punctual studies: gill nets sampling, and electrofishing sampling, genetic analyses
State of the fish communities
Functionality: Reduction of the macrophytes area (artificialization of the shoreline, agricultural practices of the catchment area
and eutrophication of the water): perturbation of the reproduction and the growth of some fish species
Stocks: Overall decrease. Roach population seems to be old, with only big fish. Pike have suffered of the decrease of
macrophytes. Whitefish, introduced for the first time in 1900, then masively in 1982, represents now 10%
of the total catches. Salmonids are very rare, because of the high summer temperature of the lake.
Carps are stocked for a fishing interest, but do not reproduce in lake.
Sanitary quality: ---
Pressures on the fish communities
Overexploitation: No
Eutrophication: No, at the opposite in step of reoligotrophication
Deterioration of the physical habitat: Artificialization of the shoreline
Invasive species: Presence of zebra mussel (Dreissena polymorpha): impact supposed on the decrease of the bleak
population ?
Management tools and specific practices
Restoration actions: In 2000, creation of 5ha of a wetland near to the emissary of the lake, allowing a function for the fish
reproduction and the expansion of the floods
Fishing management: ---
Conflicts uses regarding fishing: Some conflicts between fishermen and motorized activities on the lake
SILMAS Partner - contact for further information
Abteilung 8 Kompetenzzenturm Umwelt, Wasser und Naturschultz
Flatschacher Straße 70
A-9020 Klagenfurt, Austria
www.kis.ktn.gv.at
abt15.kis@ktn.gv.at
73

Lake WÖRTHERSEE
Austria
Characteristics
LAKE
catchment area
Surface 19.4 km 2 Surface 162 km 2
Length 16.5 km Average altitude 600 m
Width 1.7 km Maximal altitude 900 m
Altitude 439 m Population 26,832 hts
Average depth 41.9 m
Maximal depth 85.2 m
Main tributaries - Reifnitzbach
Water change time 10.5 years Emissary of the lake
Organization of the fishing activities
Lake owner: Österreichische Bundesforste AG
Fishing right owner: Alliance fishery
Regulation: Regional law
Institution in charge of the fishery: Regional authority
Main species: Whitefish, pike, lake trout (introduced in 1889), burbot, bream, roach, largemouth bass, eel…
Leisure fishing : Yes Organization: 4 leisure fishing association in reciprocity (http://www.kaerntner-fischerei.at)
Professional fishing : Yes Organization: Professional fishing but only as an annex activity
Fishing monitoring and studies
Institution: Regional authority, Lake research institute of Carinthie
Regular monitoring: Questionnaires to fishermen and fishing statistics
Specific studies: Punctual studies: gill nets sampling, and electrofishing sampling, genetic analyses
State of the fish communities
Functionality: Reduction of the macrophytes area (artificialization of the shoreline): perturbation of the reproduction and the
growth of some fish species. Impact of the motorized activities on the fish population
Stocks: Overall decrease
Sanitary quality: ---
Pressures on the fish communities
Overexploitation: Fishing exploitation is probably too high
Eutrophication: No, at the opposite in stage of reoligotrophication
Deterioration of the physical habitat: Yes
Invasive species: Eel, pumpkinseed, largemouth bass, grass carp and silver carp…
Management tools and specific practices
Restoration actions: Project of a regulation of the construction on the shoreline, which could limited the artificialization and
the decrease of habitats for fish
Fishing management: ---
Conflicts uses regarding fishing: Conflicts between fishermen and motorized activities + conflicts between leisure fishermen
and users of gill nets. The local fishing association of Carinthia, the local fishing committee
and the Regional authority have created some specific working groups in order to solve
these conflicts
SILMAS Partner - contact for further information
Abteilung 8 Kompetenzzenturm Umwelt, Wasser und Naturschultz
Flatschacher Straße 70
A-9020 Klagenfurt, Austria
www.kis.ktn.gv.at
abt15.kis@ktn.gv.at

LAke idro
Italia
Characteristics
LAKE
catchment area
Surface 11.4 km 2 Surface 617 km 2
Length 8.3 km Average altitude --- m
Width 1.8 km Maximal altitude 3,462 m
Altitude 370 m Population --- hts
Average depth 60 m
Main tributaries
- Chiese
Maximal depth 122 m
- Caffaro
Water change time 0.7 year Emissary of the lake - Chiese
Organization of the fishing activities
Lake owner: Public
Fishing right owner: ---
Regulation: Yes (legal size, periods, areas, characteristics of the nets…)
Institution in charge of the fishery: Provincia di Brescia
Main species: Rudd, chub, perche, carp, bleak, tanch, pike, lake trout, whitefish…
total of 14 species
Leisure fishing : Yes Organization: Leisure fishing using rods from the shore and from boat, and also nets and
tools for the residents of the municipalities of Idro and Anfo
Professional fishing : Yes Organization: 3 pro. fishermen
Fishing monitoring and studies
Institution: Provincia di Brescia
Regular monitoring: Fishing statistics only for professionals fishermen
Specific studies: Specific studies suggested each 5 years, according to the results of the fishing statistics
State of the fish communities
Functionality: Negative impacts of the water level changes for the species that reproduce near the shoreline ; low oxygen
concentration above the bottom of the lake
Stocks: At the beginning of the 20th, domination of the whitefish, the lake trout and the bleak (50% of the captures for
these 3 species). Today, fish populations dominated by the rudd, the perch and the bleak, mainly due to the water
quality degradation
Sanitary quality: ---
Pressures on the fish communities
Overexploitation: Fishing is a source of pressure, as the deterioration of the quality of the water of the lake has modified
structure and composition of fish population
Eutrophication: Yes, one of the main causes of the modifications of the fish populations
Deterioration of the physical habitat: Hydraulic management of the level of the lake: perturbations of the shore habitats
Invasive species: Few allochtonus species
Management tools and specific practices
Restoration actions: ---
Fishing management: Stocking for lake trout and eel
Conflicts uses regarding fishing: Conflicts between leisure and pro. fishermen. An evaluation of the fishing management
has been realized, with experts, based on technical aspects but also on issues linked to
this activity. The influence of the environment modifications on the durability of the fishing
activity was highlighted
SILMAS Partner - contact for further information
Regione Lombardia - DG Ambiente, Energia e Reti
Piazza Città di Lombardia, 1
Milano - ITALIE
www.regione.lombardia.it
daniele_magni@regione.lombardia.it
75

Lake iseo
Italia
Characteristics
LAKE
catchment area
Surface 61 km 2 Surface 1,785 km 2
Length 20.2 km Average altitude --- m
Width 3 km Maximal altitude 3,554 m
Altitude 186 m Population 191,000 hts
Average depth 125 m
Maximal depth 251 m
Main tributaries - Oglio
Water change time 4.2 years Emissary of the lake - Oglio
Organization of the fishing activities
Lake owner: ---
Fishing right owner: ---
Regulation: Regional regulation
Institution in charge of the fishery: Provincial fishing office
Main species: Whitefish, lake trout, eel, bleak, pike, perch, tanch, lake shad… total of 23 species (including 8 allochtonus)
Leisure fishing : Yes Organization: Very popular, as soon as on the shore as with a boat. Freediving spear fishing is
also allowed from dawn to dusk with spearguns, only in specific area of the lake
Professional fishing : Yes Organization: 29 licences. Increase of the age of the fishermen, few turnover
Fishing monitoring and studies
Institution: Provincial fishing office
Regular monitoring: Fishing statistics only for professional fishermen
Specific studies: Several punctual studies, focused on some species (perch, tanch…)
State of the fish communities
Functionality
and stocks: Fish populations are dominated by pelagic species (whitefish, lake shad). The perch, strongly exploited
byprofessionals fishermen, suffer from a significant reduction in bleak (food source) and a competition with
juveniles of whitefish (introduced in 1986). The reduction of the bleak population has not a known origin
(eutrophication, water level changes, increase of predators?). The arctic char reproduction is limited by the low
level of oxygen near the bottom of the lake ; lake trout reproduction is very low by the difficulty to migrate on
the spawning areas situated on the tributaries (loss of conectivity). The return of macrophytes (genus Chara and
Vallisneria) seems to be very positive for the tanch
Sanitary quality: On the lakes of the Provincia di Bergamo, a study has shown a contamination of the predators by the PCB
(pike, pikeperch), and also other species at different level
Pressures on the fish communities
Overexploitation: Difficult to evaluate; the amount of fish caught by the leisure fishermen is not known
Eutrophication: The lake has suffered from degradation, it’s today in a meso-eutrophic quality
Deterioration of the physical habitat: Dams and degradation of tributaries, degradation of the shoreline, changes in water level
Invasive species: The density of the allochtonus species are increasing since few years. Punctual presence of european
catfish. Birds feeding of fish are increasing since 20 years (cormorant, great crested grebe, grey heron…)
Management tools and specific practices
Restoration actions: In 2008, realization of a project to diversify the shoreline habitats (fascines, submerged trees, pebble
beach,vegetation….). Creation of fish passes on the tributaries
Fishing management: According a 3 years stocking plan, mainly for the lake trout
Conflicts uses regarding fishing: No actual conflicts, but increase of the leisure activities on the lake.
Presence of tools of exchanges between local stakeholders, to prevent conflicts
(regional plan, consortium of the 3 lakes, lake contract)
SILMAS Partner - contact for further information
Regione Lombardia - DG Ambiente, Energia e Reti
Piazza Città di Lombardia, 1
Milano - ITALIE
www.regione.lombardia.it
daniele_magni@regione.lombardia.it

LAke candia
Italia
Characteristics
LAKE
catchment area
Surface 1.4 km 2 Surface 8.1 km 2
Length 2.2 km Average altitude 260 m
Width 0.8 km Maximal altitude 354 m
Altitude 226 m Population 1,302 hts
Average depth 5.9 m
Main tributaries
- Sorgenti
Maximal depth 8 m
- R. della Motta
Water change time 5.7 years Emissary of the lake - C. Traversaro
Organization of the fishing activities
Lake owner: Municipality of Candia Canavese
Fishing right owner: ---
Regulation: Regional regulation + municipal regulation
Institution in charge of the fishery: ---
Main species: Bluegill (Lepomis macrochirus), rudd, black bullhead, crucian carp, carp, tanch, perch, pike
Leisure fishing : Yes Organization: Free fishing for the residents of the municipality of Candia, fishing fee for
nonresidents. Development of the «catch & release» practices
Professional fishing : No Organization: No professional fishermen, but possibility for the residents of the
municipality of Candia to use nets, but only as an annex activity and
according a specific regulation
Fishing monitoring and studies
Institution: Candia natural park authority, National Research Council, Provincia of Turin
Regular monitoring: Daily fishing reports
Specific studies: Monitoring of the pike breeding
State of the fish communities
Functionality: Good
Stocks: ---
Sanitary quality: Good
Pressures on the fish communities
Overexploitation: ---
Eutrophication: Eutrophic condition, but improvement of the quality
Deterioration of the physical habitat: ---
Invasive species: Perch, crusian carp, black bullhead, black-bass
Management tools and specific practices
Restoration actions: No
Fishing management: Stocking of pike. «Council of fishing», gathering the municipality, the Natural Park and the Provincia
of Turin
Conflicts uses regarding fishing: No
SILMAS Partner - contact for further information
ARPA Piemonte
Via della Rocca 49
10123 Torino, Italie
www.arpa.piemonte.it
urp@arpa.piemonte.it
77

lake grande di Avigliana Italia
Characteristics
LAKE
catchment area
Surface 0.9 km 2 Surface 11.5 km 2
Length 1.2 km Average altitude 400 m
Width 0.8 km Maximal altitude 641 m
Altitude 346 m Population 1,107 hts
Average depth 19.5 m
Maximal depth 26 m
Main tributaries - Rio Meana
Water change time 2.3 years Emissary of the lake - Canale Naviglio
Organization of the fishing activities
Lake owner: Italian State
Fishing right owner: Private fishing rights
Regulation: National and Provincial laws (see www.provincia.torino.it)
Institution in charge of the fishery: ---
Main species: Pike, perch, bleak, eel, crucian carp, tanch, rudd…. total of 13 species
Leisure fishing : Yes Organization: Necessity to join the National Fishing Federation
Professional fishing : No
Fishing monitoring and studies
Institution: ---
Regular monitoring: No
Specific studies: No
State of the fish communities
Functionality: ---
Stocks: ---
Sanitary quality: ---
Pressures on the fish communities
Overexploitation: ---
Eutrophication: ---
Deterioration of the physical habitat: ---
Invasive species: ---
Management tools and specific practices
Restoration actions: No
Fishing management: No
Conflicts uses regarding fishing: Yes, between fishermen and sport activities on the lake (kayak, swimmers…)
SILMAS Partner - contact for further information
ARPA Piemonte
Via della Rocca 49
10123 Torino, Italie
www.arpa.piemonte.it
urp@arpa.piemonte.it

lake Caldonazzo
Italia
Characteristics
LAKE
catchment area
Surface 5.3 km 2 Surface 49.3 km 2
Length 4.7 km Average altitude --- m
Width 1.9 km Maximal altitude 2,150 m
Altitude 449 m Population ~ 15,000 hts
Average depth 26.5 m
Maximal depth 49 m
Main tributaries - Rio Mandola
Water change time 3.6 years Emissary of the lake - Brenta
Organization of the fishing activities
Lake owner: Provincia Autonoma di Trento
Fishing right owner: Provincia Autonoma di Trento
Regulation: Provincial regulation
Institution in charge of the fishery: Provincia Autonoma di Trento
Main species: »Tibber» rudd (Scardinius scardafa), perch, pumpkinseed sunfish, black bullhead, tench, chub, carp, lake trout,
whitefish
Leisure fishing : Yes Organization: Local fishing association (Fresina - Alto Brenta). Fishermen number is stable
Professional fishing : No
Fishing monitoring and studies
Institution: Provincia Autonoma di Trento and the Forest and Fauna service
Regular monitoring: Fishing statistics (catches logbook
Specific studies: Each 2-3 years, survey of all the species of fish, in order to update the management fishing plan. Scientific
sampling with gill nets
State of the fish communities
Functionality: Lake trout are farmed in a hatchery for stocking, managed by the local fishing association
Stocks: The whitefish population is increasing, due to the improvement of the water quality. Perch is well represented, but
bleak population seems to decrease
Sanitary quality: The carp was affected by a pestilence in November 2004
Pressures on the fish communities
Overexploitation: ---
Eutrophication: ---
Deterioration of the physical habitat: ---
Invasive species: Some species, like the perch, was introduced in the past, but it is well accepted by fishermen
Management tools and specific practices
Restoration actions: Improvement of water quality thanks to a sewage collector and deep-water oxygenation
Fishing management: Stocking for lake trout (different stages), tanch, bleack, carp
Conflicts uses regarding fishing: No
SILMAS Partner - contact for further information
Agenzia Provinciale per la Protezione dell’Ambiente APPA
Piazza A. Vittoria, 5
38122 Trento, Italie
www.provincia.tn.it
maurizio.siligardi@provincia.tn.it
79

lake ledro
Italia
Characteristics
LAKE
catchment area
Surface 2.2 km 2 Surface 102 km 2
Length 2.8 km Average altitude --- m
Width 0.8 km Maximal altitude 2,254 m
Altitude 655 m Population ~ 3,500 hts
Average depth 35 m
Main tributaries
- Massangla
Maximal depth 48 m
- Springs
Water change time

lake garda
Characteristics
LAKE
Italia
(for the Trento Provincia part)
catchment area
Surface 368 km 2 Surface 2,225 km 2
Length 51.9 km Average altitude --- m
Width 16.7 km Maximal altitude 3,462 m
Altitude 65 m Population 293,210 hts
Average depth 165 m
Main tributaries
- Sarca
Maximal depth 350 m
- Toscolano
Water change time 26.8 years Emissary of the lake - Mincio
Organization of the fishing activities
Lake owner: Provincia Autonoma di Trento
Fishing right owner: Provincia Autonoma di Trento
Regulation: Provincial regulation
Institution in charge of the fishery: Provincia Autonoma di Trento
Main species: Perch, pike, rudd, roach, eel, shad (Alosa fallax), bleak, whitefish…
Leisure fishing : Yes Organization: A licence for the locals, a different one for visitors
Professional fishing : Yes Organization: Delivered by the Provincia di Trento
Fishing monitoring and studies
Institution: Provincia Autonoma di Trento and the local fishing association
Regular monitoring: Fishing statistics (catches logbook)
Specific studies: Each 2-3 years, survey of all the present species, in order to update the management fishing plan.
Scientific sampling with gill nets
State of the fish communities
Functionality: Annual artificial stocking of the lake trout
Stocks: Perch, alose and whitefish populations are well represented. Bleak population is decreasing. To note the presence of
a salmonid endemic species, «Carpione del Garda» (Salmo carpio)
Sanitary quality: ---
Pressures on the fish communities
Overexploitation: ---
Eutrophication: ---
Deterioration of the physical habitat: ---
Invasive species: Perch and whitefish have been introduced in the past
Management tools and specific practices
Restoration actions: No
Fishing management: Annual stocking for the lake trout, from spawners are catched in the Sarca. The fries are grown in a
hatchery and later release in the lake. This stocking started in 1950’ after the construction of dams on
the tributaries in order to produce hydroelectricity, that has greatly reduced or prevented the migration
of spawners
Conflicts uses regarding fishing: No
SILMAS Partner - contact for further information
Agenzia Provinciale per la Protezione dell’Ambiente APPA
Piazza A. Vittoria, 5
38122 Trento, Italie
www.provincia.tn.it
maurizio.siligardi@provincia.tn.it
81

lake levico
Italia
Characteristics
LAKE
catchment area
Surface 1,1 km 2 Surface 21,7 km 2
Length 2,8 km Average altitude --- m
Width 0,9 km Maximal altitude 1940 m
Altitude 440 m Population ~ 1 000 hts
Average depth 11,1 m
- Roggina
Main tributaries - Vignola
Maximal depth 38 m
- Maggiore
Water change time 1,1 year Emissary of the lake - Brenta
Organization of the fishing activities
Lake owner: Provincia Autonoma di Trento
Fishing right owner: Municipality of Levico Terme
Regulation: Provincial regulation
Institution in charge of the fishery: Provincia Autonoma di Trento
Main species: »Tibber» rudd (Scardinius scardafa), perch, whitefish, pumpkinseed sunfish, tench, lake trout, chub, carp,
common, nase…
Leisure fishing : Yes Organization: Local fishing association (Societa Pescatori Dilettanti Levico Terme)
Professional fishing : No
Fishing monitoring and studies
Institution: Provincia Autonoma di Trento and the local fishing association
Regular monitoring: Fishing statistics (catches book)
Specific studies: Each 2-3 years, survey of all the present species, in order to update the Management fishing plan.
Scientific sampling with gill nets
State of the fish communities
Functionality: ---
Stocks: Whitefish population is increasing, perch is well represented. The stock of bleak is decreasing
Sanitary quality: ---
Pressures on the fish communities
Overexploitation: ---
Eutrophication: ---
Deterioration of the physical habitat: ---
Invasive species: Some species, like the perch, were introduced in the past, but are well accepted by fishermen
Management tools and specific practices
Restoration actions: ---
Fishing management: Annual stocking of lake trout, tanch, carp
Conflicts uses regarding fishing: ---
SILMAS Partner - contact for further information
Agenzia Provinciale per la Protezione dell’Ambiente APPA
Piazza A. Vittoria, 5
38122 Trento, Italie
www.provincia.tn.it
maurizio.siligardi@provincia.tn.it

lake tergalo
Italia
Characteristics
LAKE
catchment area
Surface --- km 2 Surface --- km 2
Length --- km Average altitude --- m
Width --- km Maximal altitude --- m
Altitude --- m Population --- hts
Average depth --- m
Maximal depth --- m
Main tributaries ---
Water change time --- year Emissary of the lake ---
Organization of the fishing activities
Lake owner: Provincia Autonoma di Trento
Fishing right owner: Municipality of Trento
Regulation: Provincial regulation
Institution in charge of the fishery: Provincia Autonoma di Trento
Main species: Perch, pike, cyprinids
Leisure fishing : Yes Organization: Local fishing association of Trento
Professional fishing : No
Fishing monitoring and studies
Institution: Provincia Autonoma di Trento and the local fishing association
Regular monitoring: Fishing statistics (catches logbook)
Specific studies: Each 2-3 years, survey of all the present species, in order to update the management fishing plan.
Scientific sampling with gill nets
State of the fish communities
Functionality: ---
Stocks: Perch, pike and crucian carp populations are well represented
Sanitary quality: ---
Pressures on the fish communities
Overexploitation: ---
Eutrophication: ---
Deterioration of the physical habitat: ---
Invasive species: Crucian carp has been introduced in the past, but is well accepted now by fishermen
Management tools and specific practices
Restoration actions: No
Fishing management: Annual stocking of pike, tench, carp
Conflicts uses regarding fishing: No
SILMAS Partner - contact for further information
Agenzia Provinciale per la Protezione dell’Ambiente APPA
Piazza A. Vittoria, 5
38122 Trento, Italie
www.provincia.tn.it
maurizio.siligardi@provincia.tn.it
83

lake bohinj
Slovenia
Characteristics
LAKE
catchment area
Surface 3.3 km 2 Surface 107 km 2
Length 4,1 km Average altitude 1,462 m
Width 1.2 km Maximal altitude 2,586 m
Altitude 526 m Population 158 hts
Average depth 28 m
Maximal depth 45 m
Main tributaries - Savica
Water change time 0.4 year Emissary of the lake - Saca Bohinjka
Organization of the fishing activities
Lake owner: Triglav National Park
Fishing right owner: Slovenian State
Regulation: Local regulation (see http://www.bohinj.si/rd/?c=219)
Institution in charge of the fishery: National fishing Union of Slovenia and Fishing research Institute of Slovenia (since 1961)
Main species: Vairone, perch, arctic char, chub, lake trout, brown trout, rainbow trout, burbot, minnow…
total of 13 species
Leisure fishing : Yes Organization: Local fishing association of Bohinj (member of the National Union).
Fishermen number increase 3% per year, mainly with fly and spinner bait
fishing
Professional fishing : No
Fishing monitoring and studies
Institution: Local fishing association + Fishing research Institute of Slovenia
Regular monitoring: Fishing statistics: number of fishing days and overall quantity caught
Specific studies: Yes (contact the Fishing research Institute of Slovenia)
State of the fish communities
Functionality: Good: functional reproduction for all species, regulated by climate variations
Stocks: Not know precisely. In 2008, arctic char represents 75% of the total catches, and the perch almost 25 %.
Arctic char population seems to increase ; minnow population seems to decrease. Globaly the overall catches
remains pretty much the same for last few years
Sanitary quality: Good quality of the water and the fish
Pressures on the fish communities
Overexploitation: No
Eutrophication: No
Deterioration of the physical habitat: Important floods in 2006 and 2007, responsible of a strong erosion of the shoreline,
and a loss of habitats
Invasive species: Perch and minnow have been introduced in the lake by fishermen, and used as a bait for fishing
Management tools and specific practices
Restoration actions: No
Fishing management: No
Conflicts uses regarding fishing: Not really, but it’s necessary to have a better communication between all users of the lake
SILMAS Partner - contact for further information
National Institute of Biology
Vecna pot 111
1000 Ljubljana, Slovenia
www.nib.si
anton.brancelj@nib.si

Summary of the action 5.3
85

The SILMAS Project: tools for the
sustainable management of alpine lakes
SILMAS (Sustainable Instruments for Lakes
Management in the Alpine Space) is a European
project running from 2009 to 2012 for pooling
experience and know-how in terms of sustainable
management of alpine lakes.
Its goal is to produce concrete, sustainable tools
for better management of alpine lakes and in order
to raise the general public’s awareness of the
sustainable development stakes involved in the
lakes.
What is original about the SILMAS Project is that
it brings together 5 countries (Germany, Austria,
France, Italy, and Slovenia) in a varied partnership
involving local bodies, environmental authorities,
universities and research laboratories, etc.
Sustainable management of leisure
and pro. fishing at the scale of the
partnership
Within the SILMAS project, the action relating to
fisheries activities forms part of the WP5 working
group, which is dedicated to governance and the
management of conflicts which can arise due to
the various uses made of alpine lakes.
So the first objective of this action is to offer a
general overview at the level of the partnership,
of the management of fish resources and fisheries
activities. This information is summarised in the
form of sheets which are available regarding fifteen
or so lakes in the partnership.
Although the organisations and approaches differ
from country to country, region to region, and even
between lakes that lie only a few kilometres apart,
nevertheless, managers can be confronted by
similar issues. This is where pooling experiences
assumes its full importance, and this constitutes
this working group’s second objective.
Enriching feedback that is transferrable
to other lakes
Fisheries co-ordination at the level of a large
international lake is tackled through the case
of Lake Constance (Germany, Austria and
Switzerland). The experience of Lake Annecy
(France) presents the approach adopted within
a context of major exploitation by leisure and
professional fishermen. At Lake Idro (Italy), the
establishment of a Consultative Committee has
facilitated the resolution of various management
issues. The scientific monitoring undertaken at Le
Bourget Lake (France) made it possible to assess
management practices, such as restocking with
lacustrian Salmonidae. Lake Bohinj (Slovenia) is
located at the heart of a national natural park: fishing,
like other uses, is subject to special regulations.
The fish habitats of Lake Iseo (Italy) were restored
by submerging wooden structures. The managers
of Lake Serre-Ponçon (France) study the possibility
of creating artificial spawning grounds in order to
adapt to the lake’s fluctuating water levels. Lastly,
at Lake Ossiach (Austria), a vast lakeside wetlands
zone is being created, which will act as a spawning
ground.