Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 979
Title: Interactions between climate and population density in the episodic recruitment of bocaccio, Sebastes paucispinis, a Pacific rockfish
Author: Richard W. Zabel, P. S. Levin, N. Tolimieri, Nathan Mantua
Publication Year: 2012
Journal: Fisheries Oceanography
Volume: 20
Issue: 4
Pages: 294-304

Climate strongly influences the population dynamics of many species, but intrinsic and extrinsic factors such as density-dependence and anthropogenic impacts can confound the effects of climate.  Further, the temporal scale of climate response is determined by the unique characteristics of a species’ life history, and determining the most appropriate climate indicator at the proper scale is a challenge faced by population ecologists.  We focused on how climate influences juvenile survival of bocaccio (Sebastes paucispinis), a threatened Pacific rockfish, because its abundance has declined >90% in the last 25 years, ostensibly as the result of overfishing.  Bocaccio recruitment is episodic, with strong recruitment events apparently related to climate conditions.  We developed a sequence of models that related log of juvenile survival to the predictor variables population density and climate, as measured by the Northern Oscillation Index.  A model that contained only population density as a predictor variable explained only 1.4% of the variance, while a model that included only climate indices explained 52%.  Including density additively with climate did not improve model fit.  However, a model that included an interaction between density and climate explained more than 68% of the variance.  In addition, models that represented climate as monthly indices fit the juvenile survival data much better than those that averaged climate over 2- or 3- month periods.  Our results suggest that climate affects bocaccio recruitment as a series of pulses corresponding to particular life-history events, with population density mediating the magnitude of the climate effect during the settlement stage.

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Notes: 10.1111/j.1365-2419.2011.00584.x