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

NINA SPECIAL REPORT 34
being framed in terms <strong>of</strong> probability <strong>of</strong> achieving preagreed
management objectives. With many salmon stocks
around <strong>the</strong> North Atlantic presently outside
precautionary limits, and in some cases threatened or
endangered, managers are beginning to place emphasis on
seeking catch advice in terms <strong>of</strong> rebuilding objectives for
particular stocks or groups <strong>of</strong> stocks.
Cultured Atlantic salmon in nature: review
<strong>of</strong> ecology and interactions with wild fish
Bror Jonsson and Nina Jonsson
Hatchery-raised Atlantic salmon released in nature
compete with wild fish for food, space and breeding
partners. Their competitive ability differs from that <strong>of</strong> wild
fish owing to morphological, physiological, ecological and
behavioural changes which occur in hatcheries.The change
is partly phenotypic, partly genetic. The faster growth rate
<strong>of</strong> hatchery juveniles influences age and size at smolting
and maturity, reproductive output and longevity. Fastgrowing
parr tend to smolt younger, produce more but
smaller eggs, and attain maturity and die younger. Juvenile
learning influences a number <strong>of</strong> behavioural traits, and
differences in early experience appear to affect feeding
and spawning success, migratory behaviour and homing
ability. The genetic change is chiefly due to natural
selection in hatcheries with differential mortality among
genotypes, and brood stock selection based on
production traits such as large adult body mass and fast
growth rate. Due to higher aggression, experimental
evidence has revealed that hatchery parr <strong>of</strong>ten dominate
wild parr, but hatchery parr can be subordinate if smaller,
when <strong>the</strong>y co-occur in fast-flowing water and when wild
smolts have prior residence. During spawning, <strong>the</strong> fitness
<strong>of</strong> wild salmon is higher than that <strong>of</strong> hatchery-reared
conspecifics. Hatchery males do poorly in intra-sexual
competition, courting and spawning, and hatchery females
have higher egg retention, construct fewer nests, and are
less efficient in covering <strong>of</strong> <strong>the</strong> eggs in <strong>the</strong> bottom
substratum. In rivers, early survival <strong>of</strong> hatchery <strong>of</strong>fspring is
reduced compared with <strong>the</strong>ir wild counterparts.
Experimentally, it has been found that <strong>the</strong> life-time
reproductive success <strong>of</strong> farmed fish is only 1/6 <strong>of</strong> that <strong>of</strong>
similar-sized wild salmon. As a result <strong>of</strong> ecological
interactions, hatchery fish may partly displace, increase <strong>the</strong>
mortality and decrease <strong>the</strong> growth rate, adult size,
reproductive output, biomass and production <strong>of</strong> wild
conspecifics through density-dependent mechanisms.
Genetic and Ecological Interactions and
Their Management
Genetic and ecological interactions between
wild and cultured diadromous fish
Kjetil Hindar, Ian A Fleming, Phillip McGinnity and Ola Diserud
Cultured salmonids are released in large numbers, ei<strong>the</strong>r
intentionally or accidentally, and make up significant
proportions <strong>of</strong> salmonid populations in fresh and salt
water. This causes considerable concern, because
interactions between cultured fish and wild fish can
reduce <strong>the</strong> fitness and productivity <strong>of</strong> wild populations.
The interactions must be understood both within <strong>the</strong>
species’ range and outside it, as salmon aquaculture is a
worldwide enterprise. This paper reviews genetic and
ecological interactions between wild and cultured
diadromous fish, focusing on <strong>the</strong> effects <strong>of</strong> farm Atlantic
salmon (Salmo salar) on wild salmon. Farm salmon have
been under artificial selection for growth and o<strong>the</strong>r
economically important traits for 30 years, and are
genetically different from <strong>the</strong>ir origin at <strong>the</strong> molecular and
quantitative genetic level. Escaped farm salmon spawn in
<strong>the</strong> wild with limited success. Their <strong>of</strong>fspring outgrow
those <strong>of</strong> wild origin, but appear to suffer higher mortality.
Crosses between farm and wild salmon show
intermediate performance. Whole-river experiments in
Ireland and Norway show that <strong>the</strong> lifetime success <strong>of</strong> farm
salmon was reduced relative to wild salmon. The overall
productivity also appeared depressed. Based on <strong>the</strong>se
findings, we make model predictions about <strong>the</strong> future <strong>of</strong>
wild salmonid populations.
Interactions between salmon farming and
marine coastal ecosystems in <strong>the</strong> south-east
Pacific
Alejandro H Buschmann, Verónica A Riquelme, María C
Hernández-González, Daniel Varela, Jaime Jiménez, Luis A
Henríquez, Pedro A Vergara, Ricardo Guiñez and Luis Filún
Salmon aquaculture exportation in Chile reached 311,000
tons in 2004, making it <strong>the</strong> second-largest producer <strong>of</strong>
farmed salmon in <strong>the</strong> world behind Norway. Because <strong>of</strong>
this, <strong>the</strong> industry is now considered as consolidated but
with fur<strong>the</strong>r potential expansion. In order to keep on
growing, <strong>the</strong> salmon industry must expand its activities
fur<strong>the</strong>r south and thus reach pristine areas with little
human activity so far, resulting in increasing calls for
conservation actions. Never<strong>the</strong>less, <strong>the</strong> environmental
effects <strong>of</strong> salmon cultivation in sou<strong>the</strong>rn Chile remain
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