Pollock Conservation Cooperative Research Center

2003 Awarded Research Projects

PCCRC project summary (1.9 MB PDF)

Environmental predictors of walleye pollock recruitment in the Eastern Bering Sea

Award: $42,837

Estimated completion: October 31, 2004

Abstract

To develop a series of statistical models linking walleye pollock recruitment in the Eastern Bering Sea to climatic and oceanographic conditions at regional and larger spatial scales, predictor variables were carefully selected based on four general hypotheses that have been advanced to explain variations in pollock recruitment. In the first hypothesis, Wyllie-Echeverria and Wooster (1998) relate survival of larval and/or juvenile pollock to the severity of winter ice conditions and to the size and temperature of the resulting pool of cold bottom water, i.e., cold pool, on the shelf. The second and third hypotheses incorporate aspects ofthe recently proposed oscillating control hypothesis of Hunt et al. (2002). They relate pollock survival to the presence or absence of an ice-related spring bloom (Hypothesis 2) and to summer stratification and temperatures on the middle shelf region (Hypothesis 3). The fourth hypothesis examines the advection/predation hypothesis ofWespestad et al. (2000), which relates pollock recruitment to the degree of spatial separation between juvenile and cannibalistic adults. The degree of separation, in tum, is believed to be related to the passive drift of larvae into favourable or unfavourable areas. To examine the evidence for and against each of the proposed hypotheses, thus far we have obtained relevant predictor variables based on the literature and from available data sets and constructed a limited set of statistical models of recruitment.

Our overall objective is to model relationships between the recruitment or survival of larval and juvenile walleye pollock (ages 0-2), stock size, and relevant environmental variables using linear and non-linear models. These models will be used to assess the performance of each predictor variable and to assess the strength of evidence for a given hypothesis. The best models for each hypothesis will be combined into one or several models for predicting walleye pollock recruitment in the Eastern Bering Sea. The performance of the final predictive model(s) will be evaluated in a retrospective analysis and their use in stock assessment will be examined.

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