Feeding habits of wild and escaped farmed Atlantic salmon, Salmo salar L., in the Northeast Atlantic

Jacobsen, Jan Arge

doi:10.1006/jmsc.2001.1084

Cited by 109 publications

(126 citation statements)

References 31 publications

(34 reference statements)

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“…Overall, Atlantic salmon is known to display an opportunistic foraging behaviour during the ocean migration [39,40]. Thus, the temporal changes in the diving behaviour of Atlantic salmon are likely indicating flexible foraging strategies, in which individuals change their behaviour in relation to both ecological factors and seasonal light conditions.…”

Section: Vertical Movementsmentioning

confidence: 99%

Revealing the full ocean migration of individual Atlantic salmon

et al. 2018

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Background: Knowledge of the complete horizontal migration and vertical movements of Atlantic salmon (Salmo salar L.) during the marine phase is important for understanding the link between individual processes and population recruitment. We studied the detailed migration behaviour of six post-spawned adult Atlantic salmon from a North Norwegian river, during the entire ocean migration, by using high-resolution light-based geolocation archival tags. Results:The fish performed long-distance migrations and utilized Arctic areas from the eastern Barents Sea, to areas of Jan Mayen Island, and north to Svalbard. Four of six individuals exhibited a strong fidelity towards Jan Mayen Island, particularly during winter, which may suggest that the ecological conditions in these waters may be important for overwintering. One fish displayed exclusive utilization of the Barents Sea, indicating that growth and survival of some individuals are entirely dependent on these waters. The fish displayed a pelagic behaviour and all individuals spent more than 83% of the time in the uppermost 10 m of the water column. There was a strong seasonal trend in diving intensity, with the number of dives increasing with day length, independent of individuals' spatial distribution. Diving depth was positively correlated with the depth of the mixed layer. Conclusions:The Atlantic salmon displayed large individual variation in horizontal migrations, utilizing different ocean areas north of the Arctic Circle. This means that, despite the overall fidelity towards northern latitudes, individuals from the same population may experience highly different ecological conditions, potentially contributing to within-population variation in growth and survival. The seasonal correlation between diving intensity and day length, and spatial correlation between diving depth and depth of the mixed layer, indicate that the overall depth use of the Atlantic salmon depends on both spatially independent seasonal factors, and dynamic oceanographic conditions that facilitate food aggregations. This is the first study of Atlantic salmon to present detailed information about individuals' continuous horizontal migration and simultaneous vertical movements during the entire ocean migration, thus providing novel information on how habitat use change throughout the ocean residency.

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Section: Vertical Movementsmentioning

confidence: 99%

Revealing the full ocean migration of individual Atlantic salmon

et al. 2018

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“…Experimental fishing in salmon farming regions in Chile revealed that ~60% of the recaptured salmon had empty stomachs, while ~16% fed on pellets (Soto et al 2001). Jacobsen & Hansen (2001) found a considerable proportion of empty stomachs in salmon caught during autumn (47%) and winter (22%) in the Northeast Atlantic, but there were no differences between escaped farmed and wild salmon. The probability that an escaped salmon continues to feed on pellets or switches to natural prey may depend on several factors, such as locality of the escape site and season.…”

Section: Discussionmentioning

confidence: 91%

Feeding preference of recaptured Atlantic salmon Salmo salar following simulated escape from fish pens during autumn

Olsen¹,

Skilbrei²

2010

Aquacult. Environ. Interact.

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Escapes of farmed fish from coastal farms around the world are believed to have genetic and ecological consequences for wild fish populations. Each year there are numerous escapes of adult farmed Atlantic salmon Salmo salar. However, survival until maturity appears to be low. One possible explanation is that many of these salmon have difficulties switching to live prey. To address this possibility, growth rate and dietary preference were recorded in recaptured salmon released in 3 groups from August to October 2008 within a small fjord in south-western Norway (Masfjord). The fish were primed with a commercial diet containing 11% of the 'vegetable oil marker' 18:2n-6 before release. In the 14.5 to 35.1% of fish recaptured, growth rates were generally good (0.21-1.23% d -1 of fish recaptured in main fjord > 2 mo after release), with body weight doubled or more for fish recaptured after 19 wk and thereafter. However, fish recaptured in a small arm of Masfjord (Hopsvåg) had a growth rate close to zero and were in poor condition. While stomachs of recaptured fish were generally empty in the first weeks after release, pellets from fish farms were found in more than 80% of the stomachs after 12 wk and thereafter. Additionally, the level of 18:2n-6 in depot lipids (11% of fatty acids) of the muscle indicated that none of the fish recaptured the following autumn and winter in the vicinity of the release site had switched to wild prey diets. Salmon that escape during autumn are unlikely to compete for prey with wild fish in the vicinity of the release site.

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“…Escaped salmon consume much the same diet as wild salmon in oceanic waters (Hislop & Webb 1992, Jacobsen & Hansen 2001) and could potentially compete for food with wild stocks. Substantial competitive interactions in the ocean, however, appear unlikely to occur, as ocean mortality of salmon appears to be density-independent (Jonsson & Jonsson 2004), although limited information exists to assess if this is also the case for coastal waters (Jonsson & Jonsson 2006).…”

Section: Competition For Foodmentioning

confidence: 99%

Escapes of fishes from Norwegian sea-cage aquaculture: causes, consequences and prevention

Jensen¹,

Dempster²,

Thorstad³

et al. 2010

Aquacult. Environ. Interact.

252

219

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The escape of fish from aquaculture is perceived as a threat to wild fish populations. The escapes problem is largely caused by technical and operational failures of fish farming equipment. In Norway ), despite the total number of salmon held in sea-cages increasing by 44% during this period. No similar decrease in escaped cod has occurred, suggesting that other measures, such as improved netting materials for sea-cages, are required. In addition to escaping as juveniles or adults, cod may reproduce in seacages, and thus fertilised eggs escape to the environment. The ecological effects of 'escape through spawning' are unclear, and methods to inhibit escape by this mechanism are being explored. To prevent escapes of juvenile and adult fish as sea-cage aquaculture industries develop, we recommend that policy-makers implement a 5 component strategy: (1) establish mandatory reporting of all escape incidents; (2) establish a mechanism to analyse and learn from the mandatory reporting; (3) conduct mandatory, rapid, technical assessments to determine the causes of escape incidents involving more than 10 000 fish; (4) introduce a technical standard for sea-cage aquaculture equipment coupled with an independent mechanism to enforce the standard; and (5) conduct mandatory training of fish farm staff in escape-critical operations and techniques.

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Feeding habits of wild and escaped farmed Atlantic salmon, Salmo salar L., in the Northeast Atlantic

Cited by 109 publications

References 31 publications

Revealing the full ocean migration of individual Atlantic salmon

Revealing the full ocean migration of individual Atlantic salmon

Feeding preference of recaptured Atlantic salmon Salmo salar following simulated escape from fish pens during autumn

Escapes of fishes from Norwegian sea-cage aquaculture: causes, consequences and prevention

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