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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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Recapture rate of brown trout (Salmo trutta) at each electro-fishing occasion adjusted for assumed survival based on recapture rate during the preceding period.Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density. Based on estimated marginal means ± SE.
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pone-0063287-g004: Recapture rate of brown trout (Salmo trutta) at each electro-fishing occasion adjusted for assumed survival based on recapture rate during the preceding period.Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density. Based on estimated marginal means ± SE.

Mentions: At the first recapture, more starved fish were recaptured than fish from the control group in the experimental section (χ2  = 24.7, P<0.001), and analysis on starved fish only did not show any effects of density on recapture rate (χ2 = 0.4, P = 0.55; Fig. 4). This difference in recapture rate is likely due to differences in movement rather than survival (see below). At the second recapture, after adjusting for recapture rate during the first period, there were no differences among the fish due to treatment (χ2  = 1.4, P = 0.24). Recapture rates after the winter did not differ between starved and control fish (χ2  = 2.2, P = 0.14) but was higher in fish released into natural density subsection compared to high density subsections (χ2  = 4.0, P = 0.046). This finding indicates that long-term costs may be higher due to increased density effects relative to effects of starvation and/or compensatory growth.


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

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

Recapture rate of brown trout (Salmo trutta) at each electro-fishing occasion adjusted for assumed survival based on recapture rate during the preceding period.Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density. Based on estimated marginal means ± SE.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0063287-g004: Recapture rate of brown trout (Salmo trutta) at each electro-fishing occasion adjusted for assumed survival based on recapture rate during the preceding period.Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density. Based on estimated marginal means ± SE.
Mentions: At the first recapture, more starved fish were recaptured than fish from the control group in the experimental section (χ2  = 24.7, P<0.001), and analysis on starved fish only did not show any effects of density on recapture rate (χ2 = 0.4, P = 0.55; Fig. 4). This difference in recapture rate is likely due to differences in movement rather than survival (see below). At the second recapture, after adjusting for recapture rate during the first period, there were no differences among the fish due to treatment (χ2  = 1.4, P = 0.24). Recapture rates after the winter did not differ between starved and control fish (χ2  = 2.2, P = 0.14) but was higher in fish released into natural density subsection compared to high density subsections (χ2  = 4.0, P = 0.046). This finding indicates that long-term costs may be higher due to increased density effects relative to effects of starvation and/or compensatory growth.

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