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Size- and stage-dependence in cause-specific mortality of migratory brown trout

Nater, Chloé, Vindenes, Yngvild, Aass, Per, Cole, Diana J., Langangen, Øystein, Moe, S. Jannicke, Rustadbakken, Atle, Turek, Daniel, Vøllestad, L. Asbjørn, Ergon, Torbjørn and others. (2020) Size- and stage-dependence in cause-specific mortality of migratory brown trout. Journal of Animal Ecology, . ISSN 0021-8790. E-ISSN 1365-2656. (doi:10.1111/1365-2656.13269) (KAR id:81166)


Evidence‐based management of natural populations under strong human influence frequently requires not only estimates of survival but also knowledge about how much mortality is due to anthropogenic vs. natural causes. This is the case particularly when individuals vary in their vulnerability to different causes of mortality due to traits, life history stages, or locations. Here, we estimated harvest and background (other cause) mortality of landlocked migratory salmonids over half a century. In doing so, we quantified among‐individual variation in vulnerability to cause‐specific mortality resulting from differences in body size and spawning location relative to a hydropower dam. We constructed a multistate mark–recapture model to estimate harvest and background mortality hazard rates as functions of a discrete state (spawning location) and an individual time‐varying covariate (body size). We further accounted for among‐year variation in mortality and migratory behaviour and fit the model to a unique 50‐year time series of mark–recapture–recovery data on brown trout (Salmo trutta ) in Norway. Harvest mortality was highest for intermediate‐sized trout, and outweighed background mortality for most of the observed size range. Background mortality decreased with body size for trout spawning above the dam and increased for those spawning below. All vital rates varied substantially over time, but a trend was evident only in estimates of fishers' reporting rate, which decreased from over 50% to less than 10% throughout the study period. We highlight the importance of body size for cause‐specific mortality and demonstrate how this can be estimated using a novel hazard rate parameterization for mark–recapture models. Our approach allows estimating effects of individual traits and environment on cause‐specific mortality without confounding, and provides an intuitive way to estimate temporal patterns within and correlation among different mortality sources.

Item Type: Article
DOI/Identification number: 10.1111/1365-2656.13269
Uncontrolled keywords: Bayesian statistics, dam, harvesting, hazard rate, mark–recapture, mortality, NIMBLE, trout
Subjects: Q Science > QH Natural history > QH541 Ecology
Divisions: Divisions > Division of Computing, Engineering and Mathematical Sciences > School of Mathematics, Statistics and Actuarial Science
Depositing User: Diana Cole
Date Deposited: 11 May 2020 08:17 UTC
Last Modified: 04 Mar 2024 17:19 UTC
Resource URI: (The current URI for this page, for reference purposes)

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