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

NINA SPECIAL REPORT 34
Atlantic and Canada’s Pacific Coast. While significant
challenges to analysis <strong>of</strong> this data include a high degree <strong>of</strong>
natural variation, missing data, and variation in data quality,
this approach allows for direct estimation <strong>of</strong> impacts on
natural populations.
Temporal genetic stability in Atlantic salmon
populations
Øystein Skaala, Vidar Wennevik and Kevin A Glover
Every year, farmed salmon escape from sea cages and
hatcheries in high numbers. Selection programmes and
domestication have changed <strong>the</strong>ir genetic composition to
perform better in <strong>the</strong> cultured environment, and possibly
worse in natural environments. Therefore, immigration <strong>of</strong>
high numbers <strong>of</strong> escaped farmed salmon in natural salmon
stocks may potentially alter <strong>the</strong> genetic traits and cause
fitness changes in wild salmon. To investigate <strong>the</strong> temporal
stability in a number <strong>of</strong> wild Norwegian salmon stocks,
genetic pr<strong>of</strong>iles were produced from historical scale
samples and more recently collected scale material.
Salmon from Rivers Namsen, Etne, Opo,Vosso, Granvin,
Eio and Håelva were genotyped at <strong>the</strong> following
microsatellite loci: Ssa13.37, Ssa28, SsOSL85, Ssa197,
Ssa20.19, SsaF43, Ssa202, Ssa85, Ssa171, SsOSL417 and
SsOSL438. In Rivers Namsen and Etne no changes were
observed in DNA pr<strong>of</strong>iles between historical and new
samples. In River Vosso genetic stability was observed
between historical baseline and spawners up to 1997,
while a significant change was observed in later year
classes. This change corresponds in time to year classes
spawned after high immigration <strong>of</strong> farmed salmon. A
significant change in genetic pr<strong>of</strong>iles over time was also
observed in River Opo. A reduction in Fst values over
time was observed, indicating reduced level <strong>of</strong> population
differentiation.
Pros and cons <strong>of</strong> using sterile salmon in
aquaculture
Tillmann Benfey
Sterile populations are useful for <strong>the</strong> prevention <strong>of</strong>
spawning <strong>of</strong> escaped farmed fish in <strong>the</strong> wild, <strong>the</strong>
elimination <strong>of</strong> farm production losses associated with early
maturation and/or <strong>the</strong> protection <strong>of</strong> investments made in
developing novel genotypes. Given <strong>the</strong> generally reduced
performance <strong>of</strong> sterile fish in aquaculture to date, <strong>the</strong> true
need for sterile populations should be assessed on a caseby-case
basis prior to <strong>the</strong>ir large-scale use for commercial
production. This paper briefly summarizes <strong>the</strong> options
available for rendering fish reproductively sterile, and <strong>the</strong>n
32
focuses on <strong>the</strong> pros and cons <strong>of</strong> using all-female triploid
populations <strong>of</strong> Atlantic salmon for aquaculture. The mass
production <strong>of</strong> all-female triploid populations is easy and
inexpensive to achieve, although <strong>the</strong>re are some logistical
constraints with respect to broodstock requirements.
Maximizing <strong>the</strong> performance <strong>of</strong> triploid fish requires a
clear understanding <strong>of</strong> <strong>the</strong>ir unique biology as well as a
long-term commitment to selective breeding based on
triploid production characteristics. As yet, nei<strong>the</strong>r <strong>of</strong> <strong>the</strong>se
issues has been adequately addressed through commercial
culture; until this is done, <strong>the</strong> true advantages (and
disadvantages) <strong>of</strong> sterile salmon cannot be known.
Development in cage technology designed to
minimize escapes from salmon farms
Arne Fredheim
Escape <strong>of</strong> fish from fish farms is one <strong>of</strong> <strong>the</strong> major
environmental impacts caused by modern fish farming.
Reduction <strong>of</strong> <strong>the</strong> number <strong>of</strong> escapees has been a major
objective for <strong>the</strong> Norwegian fish farming industry in
recent years. The long-term aim is to reduce <strong>the</strong> extent
<strong>of</strong> escapes to a level where <strong>the</strong>y do not pose a threat to
<strong>the</strong> wild salmon. The focus on reducing escapes has
resulted in <strong>the</strong> development <strong>of</strong> technical requirements for
floating fish farms. Improvement to operations and
handling <strong>of</strong> equipment and fish to prevent accidents has
also been considered important. New fish farms have to
be certified according to technical requirements and to
prove <strong>the</strong>y have <strong>the</strong> necessary strength to withstand
environmental conditions at <strong>the</strong> particular location.
Included in <strong>the</strong> requirements are user manuals developed
by <strong>the</strong> equipment manufacturers for mounting, handling,
operating and maintaining <strong>of</strong> all equipment. To fur<strong>the</strong>r
minimize escapes from fish farms, cage design needs to
focus both on reducing probability and consequences <strong>of</strong>
accidents both with regard to technical failure and
incidents and to reduce <strong>the</strong> possibility and consequence
<strong>of</strong> incorrect use and operation <strong>of</strong> equipment. Based on
such aspects, new net cage designs and improved mooring
systems have been developed.
Conflicts between diadromous fish
restoration programmes (e.g. shad, striped
bass) and conservation <strong>of</strong> populations <strong>of</strong>
Atlantic salmon
Douglas Grout
Anadromous populations <strong>of</strong> striped bass (Morone saxatilis)
are found along <strong>the</strong> Atlantic coast <strong>of</strong> North America from
Maine to North Carolina. Recruitment overfishing