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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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Related in: MedlinePlus

Change in condition factor (a) and condition factor (b) for 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) are based on back-transformed estimated marginal means ± SE.
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pone-0063287-g003: Change in condition factor (a) and condition factor (b) for 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) are based on back-transformed estimated marginal means ± SE.

Mentions: For the first period (random factor removed with P = 0.35), starved fish increased more in condition than did control fish (F1,199  = 56.2, P<0.001), but density had no effect on condition in the starved fish (F1, 127  = 0.7, P = 0.42; Fig. 3). The effect on condition appears to arise from a relatively faster weight increase and slower length growth in starved fish compared to the control group (Fig. 2a and b). During the second period, starved fish lost less in condition than the fish in the control group (random factor removed with P = 0.26; F1,95  = 7.7, P = 0.007) probably because they started this period with a lower condition. Detailed analysis on starved fish revealed no effects of density on condition factor during the second period (F1,63  = 0.16, P = 0.69). There were no significant effects of starvation on change in condition during the last period (F1,42  = 2.27, P = 0.14). Final condition factor was the same among the groups (average 1.01 g±0.08 SD; F3,79  = 0.3, P = 0.83) matching the findings of no differences in weight and length.


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

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

Change in condition factor (a) and condition factor (b) for 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) 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-g003: Change in condition factor (a) and condition factor (b) for 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) are based on back-transformed estimated marginal means ± SE.
Mentions: For the first period (random factor removed with P = 0.35), starved fish increased more in condition than did control fish (F1,199  = 56.2, P<0.001), but density had no effect on condition in the starved fish (F1, 127  = 0.7, P = 0.42; Fig. 3). The effect on condition appears to arise from a relatively faster weight increase and slower length growth in starved fish compared to the control group (Fig. 2a and b). During the second period, starved fish lost less in condition than the fish in the control group (random factor removed with P = 0.26; F1,95  = 7.7, P = 0.007) probably because they started this period with a lower condition. Detailed analysis on starved fish revealed no effects of density on condition factor during the second period (F1,63  = 0.16, P = 0.69). There were no significant effects of starvation on change in condition during the last period (F1,42  = 2.27, P = 0.14). Final condition factor was the same among the groups (average 1.01 g±0.08 SD; F3,79  = 0.3, P = 0.83) matching the findings of no differences in weight and length.

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
Related in: MedlinePlus