Report of the 2005 ICES/NASCO Symposium on Interactions ...

NINA SPECIAL REPORT 34
combined with water quality problems led to a substantial
decline in resource abundance during <strong>the</strong> 1970s and
1980s. Cooperative interstate fishery management <strong>of</strong>
striped bass began in 1981 when an interstate fishery
management plan was developed by an organization <strong>of</strong>
Atlantic coastal states, <strong>the</strong> Atlantic States Marine Fisheries
Commission (ASMFC). Effective fishery management
under <strong>the</strong> ASMFC, combined with several key pieces <strong>of</strong>
federal legislation that streng<strong>the</strong>ned ASMFC management
and provided funding for important research and
monitoring, contributed to a 10-fold increase in
abundance <strong>of</strong> <strong>the</strong> striped bass stocks by <strong>the</strong> late 1990s.
The dramatic increase in striped bass abundance has
resulted in increased predation on <strong>the</strong> populations <strong>of</strong> a
variety <strong>of</strong> species including American shad, river herring,
and menhaden. Predation <strong>of</strong> striped bass on Atlantic
salmon smolts in North America has been documented
but no quantification <strong>of</strong> striped bass impacts on stocks <strong>of</strong>
Atlantic salmon has been conducted to date.
A review <strong>of</strong> <strong>the</strong> Pacific salmon hatchery
programmes on Hokkaido Island, Japan
Kentaro Morita,Toshihiko Saito,Yasuyuki Miyakoshi, Masa-aki
Fukuwaka,Toru Nagasawa and Masahide Kaeriyama
Hatchery programmes involving <strong>the</strong> mass release <strong>of</strong>
artificially propagated fishes have been implemented
worldwide to supplement wild populations and to
increase harvests. The island <strong>of</strong> Hokkaido in Japan is one
<strong>of</strong> <strong>the</strong> most active regions for Pacific salmon hatchery
programmes, with ca. 1.2 billion juveniles released annually
along a coastline <strong>of</strong> ca. 3000 km. In <strong>the</strong> last quarter <strong>of</strong> <strong>the</strong>
20th century, coastal catches <strong>of</strong> chum and pink salmon
increased dramatically, whereas those <strong>of</strong> masu salmon did
not. In addition to <strong>the</strong> development <strong>of</strong> hatchery
technologies, several possible hypo<strong>the</strong>ses may explain
<strong>the</strong>se catch trends, including climate change, closing <strong>of</strong>
high-seas fisheries, rehabilitation <strong>of</strong> water quality, habitat
loss caused by damming and channeling, and increased
pressure from recreational fisheries. Even when <strong>the</strong>se
o<strong>the</strong>r confounding factors have been accounted for, it is
still difficult to evaluate whe<strong>the</strong>r all hatchery programmes
have actually resulted in net population increases. To use
hatchery programmes more effectively, we need to
evaluate river- and species-specific net benefits from
hatchery programmes, and compare hatchery
programmes with o<strong>the</strong>r management tools, such as fishery
controls and habitat rehabilitation. Ra<strong>the</strong>r than resisting
change, future hatchery programmes should incorporate
active adaptive learning approaches to minimize <strong>the</strong> risks
associated with artificial propagation, and to promote
sustainable salmon stocks.
Loss <strong>of</strong> regional population structure
following stock enhancement in Atlantic
salmon
Fernando Ayllon, Jose L Martinez and Eva Garcia-Vazquez
Many wild Atlantic salmon populations were enhanced
with domesticated stocks in <strong>the</strong> past century. To evaluate
<strong>the</strong> degree and <strong>the</strong> direction <strong>of</strong> <strong>the</strong> genetic changes
produced in wild south European populations by
domesticated stocks, variation at microsatellite loci was
examined in historical and present scale collections <strong>of</strong>
seven Spanish and French populations. Significant genetic
differentiation between neighboring rivers, typical <strong>of</strong>
Atlantic salmon, existed before stock enhancement but
was lost in only a decade <strong>of</strong> stocking. Introgression <strong>of</strong>
domesticated genomes into local gene pools was
detected in <strong>the</strong> studied populations. These results show
that losing genetic diversity is a real threat for wild
populations subjected to enhancement practices.
Estimates <strong>of</strong> straying salmon Salmo salar
into rivers on <strong>the</strong> Swedish Kattegat west
coast from coastal releases in <strong>the</strong> Baltic Sea
Stig Pedersen, Gorm Rasmussen, Einar E Nielsen, Lars
Karlsson and Per Nyberg
During <strong>the</strong> years 1995-99 reared salmon from two Baltic
strains were released at <strong>the</strong> islands Bornholm and Møn in
<strong>the</strong> Baltic Sea. A total <strong>of</strong> (a) 600,000 reared salmon were
released from net pens (using <strong>the</strong> ‘delayed release’
technique, keeping <strong>the</strong> salmon in net-pens for approx.
three months after smoltification) and (b) 208,000 reared
salmon were released directly from <strong>the</strong> hatchery. Of
<strong>the</strong>se, 15,958 were tagged with Carlin tags. In <strong>the</strong> year
2000, 65,300 coded wire tagged salmon were released as
delayed release salmon close to Bornholm. Recaptures
from <strong>the</strong> Carlin tagged releases varied between 2.8 and
26.4% (average 13.1%). Recaptures in <strong>the</strong> Baltic Sea
dominated (average 98%), while a minor part <strong>of</strong> <strong>the</strong>
salmon were recaptured outside <strong>the</strong> Baltic Sea, ei<strong>the</strong>r in
<strong>the</strong> sea (1%) or in fresh water (1%). Straying rates from
<strong>the</strong>se releases into six rivers on <strong>the</strong> Swedish west coast
were estimated using information from various sources
(captures in traps, information from <strong>the</strong> sports- and brood
stock fisheries, genetic analysis). The proportion <strong>of</strong>
straying salmon was estimated to vary from 1.5 - 2% in
River Ätran to between 10 and 40% in <strong>the</strong> River Nissan,
with large variation between years. Due to <strong>the</strong> possible
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