Simulation Model of English Sole (Parophrys vetulus) Population Dynamics in Washington and Oregon Coastal Waters

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Abstract
We constructed an empirically based simulation model of population dynamics for English sole (Parophrys vetulus) occupying waters off the Washington and Oregon coast. While the original purpose for developing this model was to provide a tool for analysis of management questions, we also found it useful in evaluating hypotheses about biological processes in the early life history of sole. By comparing the ability of alternative sets of model hypotheses to reflect historical variation in abundance of age 4 recruits, we found some combinations of hypothesized mechanisms to be better than others. Approximately 61% of the interannual variation in recruitment was accounted for by a model which included (1) the effect of ocean temperatures on spawning timing, egg hatching, and fish growth, (2) density-dependent larval mortality, (3) age-dependent mortality of fish younger than age 4 yr, and (4) density-dependent growth of age 1 fish. This model explained more variation in recruitment than previous models of this population and emphasized the importance of timing of spawning on the subsequent abundance of the cohort.