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Stage-specific biomass overcompensation by juveniles in response to increased adult mortality in a wild fish population

By Jan Ohlberger, Oystein Langangen, Eric Edeline, David Claessen, Ian J. Winfield, Nils Chr. Stenseth and L. Asbjorn Vollestad


Recently developed theoretical models of stage-structured consumer–resource\ud systems have shown that stage-specific biomass overcompensation can arise in response to\ud increased mortality rates. We parameterized a stage-structured population model to simulate\ud the effects of increased adult mortality caused by a pathogen outbreak in the perch (Perca\ud fluviatilis) population of Windermere (UK) in 1976. The model predicts biomass\ud overcompensation by juveniles in response to increased adult mortality due to a shift in\ud food-dependent growth and reproduction rates. Considering cannibalism between life stages\ud in the model reinforces this compensatory response due to the release from predation on\ud juveniles at high mortality rates. These model predictions are matched by our analysis of a 60-\ud year time series of scientific monitoring of Windermere perch, which shows that the pathogen\ud outbreak induced a strong decrease in adult biomass and a corresponding increase in juvenile\ud biomass. Age-specific adult fecundity and size at age were higher after than before the disease\ud outbreak, suggesting that the pathogen-induced mortality released adult perch from\ud competition, thereby increasing somatic and reproductive growth. Higher juvenile survival\ud after the pathogen outbreak due to a release from cannibalism likely contributed to the\ud observed biomass overcompensation. Our findings have general implications for predicting\ud population- and community-level responses to increased size-selective mortality caused by\ud exploitation or disease outbreaks

Topics: Ecology and Environment
Year: 2011
DOI identifier: 10.1890/11-0410.1
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