in the Northwest Atlantic
Abstract: Predation on Atlantic salmon (Salmo salar) has been recorded in rivers and estuaries, but there is little documentation of predation at sea. Prey landed by gannets (Morus bassanus) over 24 years in a large colony off northeast Newfoundland included small proportions of post-smolt Atlantic...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.531.6579 http://www.fmap.ca/ramweb/papers-total/pred_salmon_gannets.pdf |
| Summary: | Abstract: Predation on Atlantic salmon (Salmo salar) has been recorded in rivers and estuaries, but there is little documentation of predation at sea. Prey landed by gannets (Morus bassanus) over 24 years in a large colony off northeast Newfoundland included small proportions of post-smolt Atlantic salmon. Before 1990, when shifts in oceanographic conditions and pelagic food webs occurred in the Labrador Sea, post-smolts, on average, made up 0.29 % of estimated intake by gannets during August 1977–1989. In contrast, during the 1990s, this estimate increased to 2.53%, peaking at 6.37 % in 1993. Model estimates with wide error margins projected that gannets consumed a mean of 1.6 t and 19.2 t of post-smolts during August 1977–1989 and 1990–2000, respectively, making up 0.22 % and 2.70% of estimated North American post-smolt biomass during these periods. The migratory routes of post-smolt Atlantic salmon pass through the foraging ranges of gannet colonies, but limited sampling at colonies other than Funk has not revealed salmon in gannet diets. Sampling seabird diets is an economic, biological means of investigating the ecology and natural mortality of Atlantic salmon. Spatial and temporal expansion of this sampling would enhance its oceanographic context and reduce uncertainty associated with estimates of predation by seabirds. Résumé: La prédation exercée sur le saumon de l’Atlantique (Samo salar) a été étudiée dans les rivières et les estuaires, mais elle reste mal connue en mer. Les proies capturées par les fous de Bassan (Morus bassanus) d’une grande colonie au large de la côte nord-est de Terre-Neuve au cours d’une période de 24 ans incluent une faible proportion de saumons de l’Atlantique de stade post-saumoneau. Avant 1990, lorsque les changements des conditions océaniques et des réseaux alimentaires pélagiques se sont produits, les post-saumoneaux représentaient en moyenne 0,29 % de la valeur estimée du régime alimentaire des fous durant la période d’août 1977–1989. En revanche, durant |
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