Behavioural and heart rate responses to predation risk in wild and domesticated Atlantic salmon

Abstract

Artificial culture may relax the selective pressures from predators, thereby altering behavioural and heart rate responses to predation risk. Culture may also impose new selection that adapts fish to confinement. Predictions from these hypotheses were tested by comparing seventh-generation farm Atlantic salmon (Salmo salar) with wild Atlantic salmon from the principal founder population of the farm strain. Wild age 1+ salmon had higher standard heart rates and showed a more pronounced flight and heart rate response to a simulated predator attack than did farmed salmon. However, wild fish were closer to the model predator at attack, which may have accentuated these differences. Both strains habituated to the threat, showing less response to the second attack than to the first. In contrast with age 1+ fish, wild age 2+ salmon had lower standard heart rates than farmed fish. Moreover, in age 2+ salmon, domestication effects were less clear and the response to predation threat considerably weaker, suggesting that environmental effects of culture override genetic effects as time in captivity increases. Domestication selection may thus alter reaction norms of farmed animals over environmental gradients and time. This should be considered when attempting to predict the consequences of release or escape of domesticated animals in the wild.Résumé : L'élevage en milieu artificiel diminue les pressions des prédateurs et change ainsi les réactions comportementales et physiologiques (rythme cardiaque) aux risques de prédation. L'élevage peut aussi imposer un nouveau type de sélection qui favorise l'adaptation des poissons à la restriction d'espace. La comparaison de Saumons de l'Atlantique (Salmo salar) élevés depuis 7 générations en pisciculture et de saumons sauvages provenant de la population souche principale de la pisciculture a permis de vérifier certaines prédictions générées à partir de ces hypothèses. Les saumons sauvages d'âge 1+ ont des rythmes cardiaques standard plus élevés et exhibent des réactions plus fortes de fuite et de modification du rythme cardiaque à l'attaque simulée d'un prédateur que les saumons de pisciculture. Cependant, les poissons sauvages étaient plus près du modèle de prédateur lors de l'attaque, ce qui peut avoir accentué ces différences. Les deux groupes développent une habituation aux attaques et réagissent moins fortement à une seconde attaque qu'à la première. Contrairement aux poissons d'âge 1+, les saumons sauvages d'âge 2+ ont des rythmes cardiaques standard plus bas que les saumons de pisciculture. De plus, chez les saumon d'âge 2+, les effets de la domestication sont moins apparents et les réactions à la menace de prédation sont considérablement diminuées, ce qui laisse croire que les effets environnementaux de l'élevage masquent les effets génétiques à mesure que la durée de la captivité augmente. La sélection opérée par la domestication peut ainsi modifier les normes des réactions des animaux élevés en milieu artificiel sur une gamme de gradients environnementaux et temporels. Ce s...

Can variation in standard metabolic rate explain context‐dependent performance of farmed Atlantic salmon offspring?

“…Both the reduced success of farmed salmon and their descendants in nature, and the negative effect of their presence for production of wild salmon, are likely related to genomic and phenotypic alterations that have occurred during the domestication process (Bolstad et al, 2017;Liu et al, 2017). Among the phenotypic alterations reported are increased growth rates (Gjedrem, 2000;Harvey et al, 2016;Solberg, Skaala, Nilsen, & Glover, 2013a) and changes in behavior, such as decreased response to predators, and increased aggression and social dominance (Einum & Fleming, 1997;Houde, Fraser, & Hutchings, 2010a;Johnsson, Höjesjö, & Fleming, 2001).…”

Effects of environmental fluctuations on fish metabolism: Atlantic salmon Salmo salar as a case study

“…For example, cover can potentially reduce the energetic costs incurred by station‐holding species in streams and rivers (Rimmer et al , ). Exposure to predators has been shown to increase opercular beat rate (Metcalfe et al , ) and heart rate (Höjesjö et al , ; Johnsson et al , ). Consequently, cover may allow the fish to reduce the metabolic rate by decreasing its exposure to predators.…”

The behavioral response of prey fish to predators: the role of predator size

“…Similar phenomena have been frequently documented in previous studies. For example, predator attacks induced a 50% decrease in swimming activity in Atlantic salmon ( Salmo salar ) (Johnsson, Höjesjö & Fleming, 2001; Archard & Braithwaite, 2011), and the swimming activity decreased by 38% when three-spined stickleback were exposed to chemical and visual cues of their predators (Lehtiniemi, 2005). The underlying mechanism for decreased activities in black carp when exposed to snakehead might be the result of elevated anti-predation state, including increased vigilance and a decreased possibility of detection by predators.…”

“…Moving coho salmon ( Oncorhynchus kisutch) individuals were also easier to catch for their natural predators than individuals that stayed motionless (Martel & Dill, 1995). The A reduction in activity has been frequently demonstrated in aquatic animals, including fish species, as one of the main anti-predator strategies (Brown & Smith, 1998; Johnsson, Höjesjö & Fleming, 2001; Albecker & Vance-Chalcraft, 2015; Harding & Scheibling, 2015). Such adjustments in behavior in addition to maintaining a safe distance from predators might be crucial in the survival of prey in prey-predator interactions (Martel & Dill, 1995).…”