Density-dependent mortality is mediated by foraging activity for prey fish in whole-lake experiments

Biro, Peter A., Post, John R. and Parkinson, Eric A. 2003, Density-dependent mortality is mediated by foraging activity for prey fish in whole-lake experiments, Journal of animal ecology, vol. 72, no. 4, pp. 546-555, doi: 10.1046/j.1365-2656.2003.00724.x.

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Title Density-dependent mortality is mediated by foraging activity for prey fish in whole-lake experiments
Author(s) Biro, Peter A.ORCID iD for Biro, Peter A.
Post, John R.
Parkinson, Eric A.
Journal name Journal of animal ecology
Volume number 72
Issue number 4
Start page 546
End page 555
Total pages 10
Publisher Wiley-Blackwell Publishing
Place of publication Oxford, England
Publication date 2003-07
ISSN 0021-8790
Keyword(s) activity
population consequences
Summary 1. Whereas the effects of density-dependent growth and survival on population dynamics are well-known, mechanisms that give rise to density dependence in animal populations are not well understood. We tested the hypothesis that the trade-off between growth and mortality rates is mediated by foraging activity and habitat use. Thus, if depletion of food by prey is density-dependent, and leads to greater foraging activity and risky habitat use, then visibility and encounter rates with predators must also increase.

2. We tested this hypothesis by experimentally manipulating the density of young rainbow trout (Oncorhynchus mykiss) at risk of cannibalism, in a replicated single-factor experiment using eight small lakes, during an entire growing season.

3. We found no evidence for density-dependent depletion of daphnid food in the near-shore refuge where most age-0 trout resided. Nonetheless, the proportion of time spent moving by individual age-0 trout, the proportion of individuals continuously active, and use of deeper habitats was greater in high density populations than in low density populations. Differences in food abundance among lakes had no effect on measures of activity or habitat use.

4. Mortality of age-0 trout over the growing season was higher in high density populations, and in lakes with lower daphnid food abundance. Therefore, population-level mortality of age-0 trout is linked to greater activity and use of risky habitats by individuals at high densities. We suspect that food resources were depleted at small spatial and temporal scales not detected by our plankton sampling in the high density treatment, because food-dependent activity and habitat use by age-0 trout occurs in our lakes when food abundance is experimentally manipulated
Language eng
DOI 10.1046/j.1365-2656.2003.00724.x
Field of Research 060201 Behavioural Ecology
060801 Animal Behaviour
Socio Economic Objective 970106 Expanding Knowledge in the Biological Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2003, British Ecological Society
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