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Density-dependent compensatory growth in brown trout (Salmo trutta) in nature.

Sundström LF, Kaspersson R, Näslund J, Johnsson JI - PLoS ONE (2013)

Bottom Line: We found no differences in growth, within the first month after release (May-June), between the starved fish and the control group (i.e. no evidence of compensation).Over the winter (October-April), there were no effects of either starvation or density on weight and length growth.Our results suggest that compensatory growth in nature can be density-dependent.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden. fred.sundstrom@gmail.com

ABSTRACT
Density-dependence is a major ecological mechanism that is known to limit individual growth. To examine if compensatory growth (unusually rapid growth following a period of imposed slow growth) in nature is density-dependent, one-year-old brown trout (Salmo trutta L.) were first starved in the laboratory, and then released back into their natural stream, either at natural or at experimentally increased population density. The experimental trout were captured three times over a one-year period. We found no differences in growth, within the first month after release (May-June), between the starved fish and the control group (i.e. no evidence of compensation). During the summer however (July-September), the starved fish grew more than the control group (i.e. compensation), and the starved fish released into the stream at a higher density, grew less than those released at a natural density, both in terms of weight and length (i.e. density-dependent compensation). Over the winter (October-April), there were no effects of either starvation or density on weight and length growth. After the winter, starved fish released at either density had caught up with control fish in body size, but recapture rates (proxy for survival) did not indicate any costs of compensation. Our results suggest that compensatory growth in nature can be density-dependent. Thus, this is the first study to demonstrate the presence of ecological restrictions on the compensatory growth response in free-ranging animals.

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Absolute growth in weight (a) and length (b), and growth trajectories in weight (c) and length (d) in brown trout (Salmo trutta) during each of the three periods.Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density. Values in (a) and (b) are based on back-transformed estimated marginal means ± SE.
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pone-0063287-g002: Absolute growth in weight (a) and length (b), and growth trajectories in weight (c) and length (d) in brown trout (Salmo trutta) during each of the three periods.Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density. Values in (a) and (b) are based on back-transformed estimated marginal means ± SE.

Mentions: There was no significant difference in weight growth between starved and control fish during the first period (May-June; random factor retained with P = 0.13, treatment: F1,15.4  = 0.94, P = 0.35). However, a clear compensatory growth response is observed for the second period (Jul-Sep) when starved fish grew more in weight than did control fish (random factor removed with P = 0.35, F1,95  = 11.8, P<0.001). Analysis of density effects, by including the starved fish only, showed that those fish at a natural density gained on average 17% more in weight than those fish at a higher density (F1,63  = 4.2, P = 0.045), indicating the presence of density-dependent compensatory growth during this period (Fig. 2a). There were no significant differences in weight growth between starved and control fish during the last period (Oct-Apr; F1,42  = 0.01, P = 0.91) which was clearly associated with an increased variation in growth among individuals (Fig. 2a). Final weight of the four groups were similar (overall average 20.5 g±5.9 SD; one-way ANOVA F3,79  = 0.2, P = 0.91) suggesting that a complete catch-up in weight had been achieved by the starved fish at both the high and natural density.


Density-dependent compensatory growth in brown trout (Salmo trutta) in nature.

Sundström LF, Kaspersson R, Näslund J, Johnsson JI - PLoS ONE (2013)

Absolute growth in weight (a) and length (b), and growth trajectories in weight (c) and length (d) in brown trout (Salmo trutta) during each of the three periods.Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density. Values in (a) and (b) are based on back-transformed estimated marginal means ± SE.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3643939&req=5

pone-0063287-g002: Absolute growth in weight (a) and length (b), and growth trajectories in weight (c) and length (d) in brown trout (Salmo trutta) during each of the three periods.Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density. Values in (a) and (b) are based on back-transformed estimated marginal means ± SE.
Mentions: There was no significant difference in weight growth between starved and control fish during the first period (May-June; random factor retained with P = 0.13, treatment: F1,15.4  = 0.94, P = 0.35). However, a clear compensatory growth response is observed for the second period (Jul-Sep) when starved fish grew more in weight than did control fish (random factor removed with P = 0.35, F1,95  = 11.8, P<0.001). Analysis of density effects, by including the starved fish only, showed that those fish at a natural density gained on average 17% more in weight than those fish at a higher density (F1,63  = 4.2, P = 0.045), indicating the presence of density-dependent compensatory growth during this period (Fig. 2a). There were no significant differences in weight growth between starved and control fish during the last period (Oct-Apr; F1,42  = 0.01, P = 0.91) which was clearly associated with an increased variation in growth among individuals (Fig. 2a). Final weight of the four groups were similar (overall average 20.5 g±5.9 SD; one-way ANOVA F3,79  = 0.2, P = 0.91) suggesting that a complete catch-up in weight had been achieved by the starved fish at both the high and natural density.

Bottom Line: We found no differences in growth, within the first month after release (May-June), between the starved fish and the control group (i.e. no evidence of compensation).Over the winter (October-April), there were no effects of either starvation or density on weight and length growth.Our results suggest that compensatory growth in nature can be density-dependent.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden. fred.sundstrom@gmail.com

ABSTRACT
Density-dependence is a major ecological mechanism that is known to limit individual growth. To examine if compensatory growth (unusually rapid growth following a period of imposed slow growth) in nature is density-dependent, one-year-old brown trout (Salmo trutta L.) were first starved in the laboratory, and then released back into their natural stream, either at natural or at experimentally increased population density. The experimental trout were captured three times over a one-year period. We found no differences in growth, within the first month after release (May-June), between the starved fish and the control group (i.e. no evidence of compensation). During the summer however (July-September), the starved fish grew more than the control group (i.e. compensation), and the starved fish released into the stream at a higher density, grew less than those released at a natural density, both in terms of weight and length (i.e. density-dependent compensation). Over the winter (October-April), there were no effects of either starvation or density on weight and length growth. After the winter, starved fish released at either density had caught up with control fish in body size, but recapture rates (proxy for survival) did not indicate any costs of compensation. Our results suggest that compensatory growth in nature can be density-dependent. Thus, this is the first study to demonstrate the presence of ecological restrictions on the compensatory growth response in free-ranging animals.

Show MeSH