A Model of Chinook Salmon Population Dynamics Incorporating Size-selective Exploitation and Inheritance of Polygenic Correlated Traits

Concern regarding the potential for selective fisheries to degrade desirable characteristics of exploited fish populations is growing worldwide. Although the occurrence of fishery-induced evolution in a wild population has not been irrefutably documented, considerable theoretical and empirical evidence for that possibility exists. Environmental conditions influence survival and growth in many species and may mask comparatively subtle trends induced by selective exploitation, especially given the evolutionarily short time series of data available from many fisheries. Modeling may be the most efficient investigative tool under such conditions. Motivated by public concern that large-mesh gillnet fisheries may be altering Chinook salmon in western Alaska, we constructed a stochastic model of the population dynamics of Chinook salmon. The model contained several individually based components and incorporated size-selective exploitation, assortative mating, size-dependent female fecundity, density-dependent survival, and the heritability of size and age. Substantial reductions in mean size and age were observed under all scenarios. Concurrently reducing directional selection and increasing spawning abundance was most effective in stimulating population ∗Corresponding author. J. F. Bromaghin, U.S. Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, Alaska 99508; e-mail: [email protected]. Received by the editors on 20th August, 2009. Accepted 1s t August, 2010. Copyright c © 2010 W iley Period ica ls, Inc.