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

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.