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Growth reaction norms of domesticated, wild and hybrid Atlantic salmon families in response to differing social and physical environments.

Solberg MF, Zhang Z, Nilsen F, Glover KA - BMC Evol. Biol. (2013)

Bottom Line: The main results of this study, which are based upon the analysis of more than 6000 juvenile salmon, can be summarised as; (i) there was no difference in relative growth between wild and farmed salmon when reared together and separately; (ii) the relative difference in body weight at termination between wild and farmed salmon decreased as mortality increased along the environmental gradient approaching natural conditions.This study demonstrates that potential social interactions between wild and farmed salmon when reared communally are not likely to cause an overestimation of the genetic growth differences between them.Therefore, common-garden experiments represent a valid methodological approach to investigate genetic differences between wild and farmed salmon.

View Article: PubMed Central - HTML - PubMed

Affiliation: Section of Population Genetics and Ecology, Institute of Marine Research, P,O, Box 1870, Nordnes, NO-5817 Bergen, Norway. monica.solberg@imr.no.

ABSTRACT

Background: Directional selection for growth has resulted in the 9-10th generation of domesticated Atlantic salmon Salmo salar L. outgrowing wild salmon by a ratio of approximately 3:1 when reared under standard hatchery conditions. In the wild however, growth of domesticated and wild salmon is more similar, and seems to differ at the most by a ratio of 1.25:1. Comparative studies of quantitative traits in farmed and wild salmon are often performed by the use of common-garden experiments where salmon of all origins are reared together to avoid origin-specific environmental differences. As social interaction may influence growth, the large observed difference in growth between wild and domesticated salmon in the hatchery may not be entirely genetically based, but inflated by inter-strain competition. This study had two primary aims: (i) investigate the effect of social interaction and inter-strain competition in common-garden experiments, by comparing the relative growth of farmed, hybrid and wild salmon when reared together and separately; (ii) investigate the competitive balance between wild and farmed salmon by comparing their norm of reaction for survival and growth along an environmental gradient ranging from standard hatchery conditions to a semi-natural environment with restricted feed.

Results: The main results of this study, which are based upon the analysis of more than 6000 juvenile salmon, can be summarised as; (i) there was no difference in relative growth between wild and farmed salmon when reared together and separately; (ii) the relative difference in body weight at termination between wild and farmed salmon decreased as mortality increased along the environmental gradient approaching natural conditions.

Conclusions: This study demonstrates that potential social interactions between wild and farmed salmon when reared communally are not likely to cause an overestimation of the genetic growth differences between them. Therefore, common-garden experiments represent a valid methodological approach to investigate genetic differences between wild and farmed salmon. As growth of surviving salmon of all origins became more similar as mortality increased along the environmental gradient approaching natural conditions, a hypothesis is presented suggesting that size-selective mortality is a possible factor reducing growth differences between these groups in the wild.

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Growth reaction norms across treatments, experiment II. Mean weight (log10) norm of reaction across all treatments for salmon of farmed, hybrid and wild origin. Replicated tanks are pooled. Error bars show the range of the family means within each experimental group. The elevations of the reaction norms were significantly different between the treatments, as well as between the farmed, hybrid and wild salmon. Wild salmon displayed a significantly flatter negative reaction norm slope between the hatchery control and the restricted hatchery treatments than the hybrid and farmed salmon, which displayed similar and steeper slopes. All groups displayed significantly different reaction norm slopes between the hatchery control and the restricted semi-natural treatment, with farmed salmon displaying the steepest slope, followed by the hybrid salmon. Salmon of all origin displayed similar positive reaction norm slopes between the restricted hatchery treatment and the restricted semi-natural treatment.
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Figure 8: Growth reaction norms across treatments, experiment II. Mean weight (log10) norm of reaction across all treatments for salmon of farmed, hybrid and wild origin. Replicated tanks are pooled. Error bars show the range of the family means within each experimental group. The elevations of the reaction norms were significantly different between the treatments, as well as between the farmed, hybrid and wild salmon. Wild salmon displayed a significantly flatter negative reaction norm slope between the hatchery control and the restricted hatchery treatments than the hybrid and farmed salmon, which displayed similar and steeper slopes. All groups displayed significantly different reaction norm slopes between the hatchery control and the restricted semi-natural treatment, with farmed salmon displaying the steepest slope, followed by the hybrid salmon. Salmon of all origin displayed similar positive reaction norm slopes between the restricted hatchery treatment and the restricted semi-natural treatment.

Mentions: Fish size upon termination of the experiment was significantly higher in the hatchery control treatment than in the restricted hatchery treatment and the restricted semi-natural treatment (Tables 3 and 4; Figure 7). Fish size was significantly higher in the restricted semi-natural treatment than in the restricted hatchery treatment, despite the fact that fewer degree days had elapsed in the restricted semi-natural treatment upon termination (Tables 1, 3 and 4; Figure 7). Thus, the general growth reaction norm slope between the hatchery control treatment and both the restricted hatchery treatment and the restricted semi-natural treatment was negative, while the slope between the restricted hatchery treatment and the semi-natural treatment was positive (Figure 8).


Growth reaction norms of domesticated, wild and hybrid Atlantic salmon families in response to differing social and physical environments.

Solberg MF, Zhang Z, Nilsen F, Glover KA - BMC Evol. Biol. (2013)

Growth reaction norms across treatments, experiment II. Mean weight (log10) norm of reaction across all treatments for salmon of farmed, hybrid and wild origin. Replicated tanks are pooled. Error bars show the range of the family means within each experimental group. The elevations of the reaction norms were significantly different between the treatments, as well as between the farmed, hybrid and wild salmon. Wild salmon displayed a significantly flatter negative reaction norm slope between the hatchery control and the restricted hatchery treatments than the hybrid and farmed salmon, which displayed similar and steeper slopes. All groups displayed significantly different reaction norm slopes between the hatchery control and the restricted semi-natural treatment, with farmed salmon displaying the steepest slope, followed by the hybrid salmon. Salmon of all origin displayed similar positive reaction norm slopes between the restricted hatchery treatment and the restricted semi-natural treatment.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231500&req=5

Figure 8: Growth reaction norms across treatments, experiment II. Mean weight (log10) norm of reaction across all treatments for salmon of farmed, hybrid and wild origin. Replicated tanks are pooled. Error bars show the range of the family means within each experimental group. The elevations of the reaction norms were significantly different between the treatments, as well as between the farmed, hybrid and wild salmon. Wild salmon displayed a significantly flatter negative reaction norm slope between the hatchery control and the restricted hatchery treatments than the hybrid and farmed salmon, which displayed similar and steeper slopes. All groups displayed significantly different reaction norm slopes between the hatchery control and the restricted semi-natural treatment, with farmed salmon displaying the steepest slope, followed by the hybrid salmon. Salmon of all origin displayed similar positive reaction norm slopes between the restricted hatchery treatment and the restricted semi-natural treatment.
Mentions: Fish size upon termination of the experiment was significantly higher in the hatchery control treatment than in the restricted hatchery treatment and the restricted semi-natural treatment (Tables 3 and 4; Figure 7). Fish size was significantly higher in the restricted semi-natural treatment than in the restricted hatchery treatment, despite the fact that fewer degree days had elapsed in the restricted semi-natural treatment upon termination (Tables 1, 3 and 4; Figure 7). Thus, the general growth reaction norm slope between the hatchery control treatment and both the restricted hatchery treatment and the restricted semi-natural treatment was negative, while the slope between the restricted hatchery treatment and the semi-natural treatment was positive (Figure 8).

Bottom Line: The main results of this study, which are based upon the analysis of more than 6000 juvenile salmon, can be summarised as; (i) there was no difference in relative growth between wild and farmed salmon when reared together and separately; (ii) the relative difference in body weight at termination between wild and farmed salmon decreased as mortality increased along the environmental gradient approaching natural conditions.This study demonstrates that potential social interactions between wild and farmed salmon when reared communally are not likely to cause an overestimation of the genetic growth differences between them.Therefore, common-garden experiments represent a valid methodological approach to investigate genetic differences between wild and farmed salmon.

View Article: PubMed Central - HTML - PubMed

Affiliation: Section of Population Genetics and Ecology, Institute of Marine Research, P,O, Box 1870, Nordnes, NO-5817 Bergen, Norway. monica.solberg@imr.no.

ABSTRACT

Background: Directional selection for growth has resulted in the 9-10th generation of domesticated Atlantic salmon Salmo salar L. outgrowing wild salmon by a ratio of approximately 3:1 when reared under standard hatchery conditions. In the wild however, growth of domesticated and wild salmon is more similar, and seems to differ at the most by a ratio of 1.25:1. Comparative studies of quantitative traits in farmed and wild salmon are often performed by the use of common-garden experiments where salmon of all origins are reared together to avoid origin-specific environmental differences. As social interaction may influence growth, the large observed difference in growth between wild and domesticated salmon in the hatchery may not be entirely genetically based, but inflated by inter-strain competition. This study had two primary aims: (i) investigate the effect of social interaction and inter-strain competition in common-garden experiments, by comparing the relative growth of farmed, hybrid and wild salmon when reared together and separately; (ii) investigate the competitive balance between wild and farmed salmon by comparing their norm of reaction for survival and growth along an environmental gradient ranging from standard hatchery conditions to a semi-natural environment with restricted feed.

Results: The main results of this study, which are based upon the analysis of more than 6000 juvenile salmon, can be summarised as; (i) there was no difference in relative growth between wild and farmed salmon when reared together and separately; (ii) the relative difference in body weight at termination between wild and farmed salmon decreased as mortality increased along the environmental gradient approaching natural conditions.

Conclusions: This study demonstrates that potential social interactions between wild and farmed salmon when reared communally are not likely to cause an overestimation of the genetic growth differences between them. Therefore, common-garden experiments represent a valid methodological approach to investigate genetic differences between wild and farmed salmon. As growth of surviving salmon of all origins became more similar as mortality increased along the environmental gradient approaching natural conditions, a hypothesis is presented suggesting that size-selective mortality is a possible factor reducing growth differences between these groups in the wild.

Show MeSH
Related in: MedlinePlus