A CATCH-AT-LENGTH ANALYSIS THAT INCORPORATES A STOCHASTIC-MODEL OF GROWTH

A length-structured population model, which incorporates von Bertalanffy growth, is used to describe changes in population abundance over time. The model is incorporated into a catch-at-length algorithm that uses a non-linear least squares approach to estimate relative abundance, fishing mortality, selectivity, and the von Bertalanffy growth parameters L∞ and k. The algorithm is applied to a simulated data set for Pacific cod Gadus macrocephalus and to catch data on Pseudotolithus typus and Decapterus russellii. Estimated population and exploitation parameters fit the observed catch-at-length. Estimates made with the catch-at-length approach can be improved by using auxiliary information that may be available on abundance, fishing effort, recruitment and growth. -from Authors