Limits...
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.

Show MeSH
Movements of brown trout (Salmo trutta) during each of the three periods.Box-and-whisker plot showing median (vertical line inside box), 25 and 75 percentiles (edge of box), 10 and 90 percentiles (whiskers) and individual data points beyond (filled circle). Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3643939&req=5

pone-0063287-g005: Movements of brown trout (Salmo trutta) during each of the three periods.Box-and-whisker plot showing median (vertical line inside box), 25 and 75 percentiles (edge of box), 10 and 90 percentiles (whiskers) and individual data points beyond (filled circle). Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density.

Mentions: The number of fish in the control group that moved more than 20 m, were higher than the number of starved fish that moved more than 20 m during the first period (χ2  = 9.4, P = 0.002; Fig. 5), which may help explain the lower recapture rates in fish from the control group after this period of only one month (Fig. 4). Among the starved fish, individuals at the high density were more likely to move compared to those at the natural density (χ2  = 6.7, P = 0.009). During the second period, there was no effect of the starvation treatment (χ2  = 0.73, P = 0.39), but overall more fish moved at the high density compared to the low density (χ2  = 6.6, P = 0.010). During the last period, all fish from the control group at the high density had moved more than 20 m so this data could not be analyzed using the full model. Analysis of the starved fish did not indicate any effect of density on movement (χ2  = 0.31, P = 0.58).


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

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

Movements of brown trout (Salmo trutta) during each of the three periods.Box-and-whisker plot showing median (vertical line inside box), 25 and 75 percentiles (edge of box), 10 and 90 percentiles (whiskers) and individual data points beyond (filled circle). Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0063287-g005: Movements of brown trout (Salmo trutta) during each of the three periods.Box-and-whisker plot showing median (vertical line inside box), 25 and 75 percentiles (edge of box), 10 and 90 percentiles (whiskers) and individual data points beyond (filled circle). Fish were starved (starved) or not (control) in the laboratory followed by release to nature at a natural (natural) or experimentally increased (high) density.
Mentions: The number of fish in the control group that moved more than 20 m, were higher than the number of starved fish that moved more than 20 m during the first period (χ2  = 9.4, P = 0.002; Fig. 5), which may help explain the lower recapture rates in fish from the control group after this period of only one month (Fig. 4). Among the starved fish, individuals at the high density were more likely to move compared to those at the natural density (χ2  = 6.7, P = 0.009). During the second period, there was no effect of the starvation treatment (χ2  = 0.73, P = 0.39), but overall more fish moved at the high density compared to the low density (χ2  = 6.6, P = 0.010). During the last period, all fish from the control group at the high density had moved more than 20 m so this data could not be analyzed using the full model. Analysis of the starved fish did not indicate any effect of density on movement (χ2  = 0.31, P = 0.58).

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