Cultured Atlantic salmon in nature: a review of their ecology and interaction with wild fish

Abstract

N. 2006. Cultured Atlantic salmon in nature: a review of their ecology and interaction with wild fish. e ICES Journal of Marine Science, 63: 1162e1181.When cultured Atlantic salmon are released into nature, they compete with wild fish for food, space, and breeding partners. As a result of morphological, physiological, ecological, and behavioural changes that occur in hatcheries, their comp etitive ability often differs from that of wild fish. These changes are partly phenotypic and partly genetic. Cultured juveniles' faster growth rate influences age and size at smolting and maturity, reproductive output, and longevity. Fast-growing parr tend to smolt younger, produce more but smaller eggs, attain maturity earlier, and die younger. Juvenile learning influences a number of behavioural traits, and differences in early experience appear to affect feeding and spawning success, migratory behaviour, and homing ability. Genetic change in hatcheries is chiefly the result of natural selection, with differential mortality among genotypes and broodstock selection based on production traits such as high adult body mass and fast growth rate. Experimental evidence has revealed that cultured parr's greater aggression often allows them to dominate wild parr, although smaller cultured parr can be subordinated if they co-occur in fast-flowing water and if wild smolts have established prior residence. During spawning, the fitness of wild salmon is superior to that of cultured conspecifics. Cultured males are inferior to wild males in intra-sexual competition, courting, and spawning; cultured females have greater egg retention, construct fewer nests, and are less efficient at covering their eggs in the substratum than their wild counterparts. In rivers, the early survival of cultured offspring is lower than that of their wild counterparts. The lifetime reproductive success of farmed fish has been estimated at 17% that of similar-sized wild salmon. As a result of ecological interaction and through density-dependent mechanisms, cultured fish may displace wild conspecifics to some extent, increase their mortality, and decrease their growth rate, adult size, reproductive output, biomass, and production.

Native and exotic fishes in a Patagonian reservoir with rainbow trout cage culture: spatial and trophic resource use

“…This pattern could be favored by enhanced prey availability near the farms, as has been suggested for Canadian lakes (Podemski and Blanchfield, 2006). The comparison of body shape to assess nutritional status between farmed escapees and their free-living conspecifics is known to be affected by shape differences resulting from particular rearing environment and genetics (Swain et al, 1991;Jonsson and Jonsson, 2006;Consuegra et al, 2011). In this regard, our results showed a deeper body shape (higher body condition, SMI) for ERT compared to WRT.…”

Restoration of native Atlantic salmon runs in northern Spain: do costs outweigh benefits?

“…This approach does nothing to correct the basic problem of Spanish salmon rivers (impassable dams) and introduces hatchery-reared salmon into wild areas in the rivers to which they are poorly suited and may exert a negative impact on native populations (e.g. McGinnity et al, 2003;Moran et al, 2005;Ayllon et al, 2006;Jonsson and Jonsson, 2006). In fact, our results show that in % foreign genomes (1996) 5% 6.68% Ayllon et al (2006) the River Nalon-Narcea there was no significant association between stocking and catch despite high stocking efforts.…”

Collaboration between Atlantic and Pacific salmon biologists to enhance recovery of endangered salmon in North America

“…Hatchery-origin fish have also been shown to have negative fitness impacts on wild populations (e.g., Jonsson and Jonsson 2006;Araki et al 2008). Therefore, in a conservation context, managers spend extensive resources to evaluate benefits and risks of using hatchery-origin fish to aid in recovery of endangered natural populations (Waples 1999;Baskett and Waples 2013).…”