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

Biro, PA; Post, JR; Parkinson, EA

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

Biro, PA

Post, JR Parkinson, EA

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Publication Type:: Journal Article
Citation:: J Anim Ecol, 2003, 72 (4), pp. 546 - 555
Issue Date:: 2003-07

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Field	Value	Language
dc.contributor.author	Biro, PA https://orcid.org/0000-0002-3565-240X	en_US
dc.contributor.author	Post, JR	en_US
dc.contributor.author	Parkinson, EA	en_US
dc.date.issued	2003-07	en_US
dc.identifier.citation	J Anim Ecol, 2003, 72 (4), pp. 546 - 555	en_US
dc.identifier.uri	http://hdl.handle.net/10453/8704
dc.description.abstract	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. 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. We found no evidence for density-dependent depletion of daphnid food in the nearshore 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. 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 (Biro, Post & Parkinson, in press).	en_US
dc.language	eng	en_US
dc.relation.ispartof	J Anim Ecol	en_US
dc.relation.isbasedon	10.1046/j.1365-2656.2003.00724.x	en_US
dc.subject.classification	Ecology	en_US
dc.title	Density-dependent mortality is mediated by foraging activity for prey fish in whole-lake experiments.	en_US
dc.type	Journal Article
utslib.citation.volume	4	en_US
utslib.citation.volume	72	en_US
utslib.location.activity	England	en_US
utslib.for	0602 Ecology	en_US
utslib.for	05 Environmental Sciences	en_US
utslib.for	06 Biological Sciences	en_US
utslib.for	07 Agricultural and Veterinary Sciences	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
utslib.copyright.status	closed_access
pubs.issue	4	en_US
pubs.publication-status	Published	en_US
pubs.volume	72	en_US

Abstract:

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. 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. We found no evidence for density-dependent depletion of daphnid food in the nearshore 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. 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 (Biro, Post & Parkinson, in press).

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http://hdl.handle.net/10453/8704