Domestication and growth hormone alter antipredator behaviour and growth patterns in juvenile brown trout, &lt;I&gt;Salmo trutta&lt;/I&gt;

Johnsson, J. I.; Petersson, Erik; Jönsson, Elisabeth; Björnsson, Björn Th.; Järvi, Torbjörn

doi:10.1139/cjfas-53-7-1546

Cited by 25 publications

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“…Alternatively, some studies have suggested that fish that produce more growth hormone (and have a faster growth rate as a consequence) have a more reduced antipredator response because they have a higher need to forage and may be more willing to take risks (e.g. Johnsson and Björnsson 1994;Johnsson et al 1996;Fleming and Einum 1997). Nevertheless, differences in refuge time between farmed and wild fry in the present study could not be explained by differences in growth rate.…”

Section: Discussionmentioning

confidence: 49%

Reduced anti-predator responses in multi-generational hybrids of farmed and wild Atlantic salmon (Salmo salar L.)

2009

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Cultured organisms undergo genetically-based behavioural changes that may reduce their ability to survive in the wild. This has raised concerns that interbreeding between escaped cultured and wild organisms will generate hybrids exhibiting maladaptive behaviours which may ultimately reduce the fitness of the wild counterpart. We compared anti-predator responses in Atlantic salmon (Salmo salar) from two wild North American populations, the major farmed strain used in regional aquaculture, and their wild-farmed hybrids (F 1 , F 2 , and wild backcross). Anti-predator responses of fry (age 0? parr) were measured under common environmental conditions, using a model of a natural predator (belted kingfisher, Ceryle alcyon). Farmed fry exhibited significantly reduced antipredator responses relative to fry from both wild populations. The anti-predator responses of wild-farmed hybrid fry were intermediate to those of the parental populations (pure farmed or wild). The magnitude by which wildfarmed hybrids differed in anti-predator responses from pure wild fish also depended on the wild population. These results suggest that: (1) the observed behavioural differences have a genetic basis; (2) wild-farmed hybrids have, on average, reduced anti-predator responses relative to wild fish; and that (3) the effects of wild-farmed interbreeding on anti-predator responses will differ between wild populations. Our study is consistent with the general hypothesis that continual farmed-wild interbreeding may have detrimental effects on the fitness of wild organisms.

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Section: Discussionmentioning

confidence: 49%

Reduced anti-predator responses in multi-generational hybrids of farmed and wild Atlantic salmon (Salmo salar L.)

2009

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“…We used offspring of sea-ranched anadromous brown trout (Salmo trutta) originating from the River Dalälven (for strain information see Johnsson et al 1996). Trout were artificially fertilized at the Swedish board of Fisheries in Ä lvkarleby on 31 October 2006, when eggs from 11 females were fertilized by milt from 11 males.…”

Section: (A) Experimental Fishmentioning

confidence: 99%

Less is more: density influences the development of behavioural life skills in trout

2010

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Theory suggests that habitat structure and population density profoundly influence the phenotypic development of animals. Here, we predicted that reduced rearing density and increased structural complexity promote food search ability, anti-predator response and the ability to forage on novel prey, all behavioural skills important for surviving in the wild. Brown trout were reared at three densities (conventional hatchery density, a fourth of conventional hatchery density and natural density) in tanks with or without structure. Treatment effects on behaviour were studied on trout fry and parr, whereupon 20 trout from each of the six treatment groups were released in an enclosed natural stream and recaptured after 36 days. Fry reared at natural density were faster to find prey in a maze. Moreover, parr reared at natural density were faster to eat novel prey, and showed more efficient anti-predator behaviour than fish reared at higher densities. Furthermore, parr reared at reduced densities were twice as likely to survive in the stream as trout reared at high density. In contrast, we found no clear treatment effects of structure. These novel results suggest that reduced rearing densities can facilitate the development of behavioural life skills in captive animals, thereby increasing their contribution to natural production.

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Growth hormone‐induced effects on mortality, energy status and growth: a field study on Brown Trout (Salmo trutta)

et al. 1999

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1. Growth hormone (GH) treatment increases the growth rate and competitive ability of salmonids under laboratory conditions. Since fast growth should increase fitness, why is endogenous secretion of GH not higher in wild fish? To address this question, three hypotheses were suggested. H1: high GH levels reduce antipredator responses and may therefore increase mortality from predation. H2: high GH levels reduce long‐term (e.g. over winter) survival by reducing allocation to critical energy reserves. H3: GH is not beneficial for growth under natural conditions. 2. To test these hypotheses, the performance of GH‐treated juvenile Brown Trout (Salmo trutta) and control (placebo) trout was compared in an enclosed stream section subjected to natural predation. Four experiments were conducted during winter, spring, summer and autumn, respectively. 3. Mortality rates were not significantly different between GH‐treated and control trout in any of the four experiments so H1 was not supported. Energy reserves were generally lower in GH‐treated fish, which is consistent with H2, whereas growth rates in mass were higher in GH‐treated fish than in controls so H3 was not supported. This suggests that GH promotes growth at the expense of investment in maintenance. 4. Judging from growth and mortality rates, the fitness of GH‐treated and control trout appeared similar. Thus, escaped GH‐manipulated fish may compete successfully with wild fish. 5. Hatchery‐raised trout with higher initial condition index suffered higher mortality rates than more slender fish. This novel finding may be explained by reduced escape ability related to body morphology, reduced behavioural responses towards predators by high‐condition trout, or predator preferences for high‐condition fish.

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Domestication and growth hormone alter antipredator behaviour and growth patterns in juvenile brown trout, <I>Salmo trutta</I>

Cited by 25 publications

References 0 publications

Reduced anti-predator responses in multi-generational hybrids of farmed and wild Atlantic salmon (Salmo salar L.)

Reduced anti-predator responses in multi-generational hybrids of farmed and wild Atlantic salmon (Salmo salar L.)

Less is more: density influences the development of behavioural life skills in trout

Growth hormone‐induced effects on mortality, energy status and growth: a field study on Brown Trout (Salmo trutta)

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