Integrating the standardization of catch-per-unit-of-effort into stock assessment models: testing a population dynamics model and using multiple data types

Standardization of catch-per-unit-of-effort (CPUE) data can be integrated into stock assessment methods. We apply this method to the stock of trevally (Pseudocaranx dentex) off the west coast of New Zealand to address: (1) whether the stock assessment model explains all of the annual variation in the CPUE data, and (2) the impact on the assessment results of how the catch-at-age data are weighted. If not all of annual variation in CPUE is explained by the stock assessment model, the assessment may be statistically inadequate. The inadequacy may be in the representation of the population dynamics, in the relationship between CPUE and abundance, or due to additional variation in CPUE left unexplained by the independent variables. Catch-at-age data often have too much influence on the estimated abundance trajectory, so the sample size used in the catch-at-age likelihood function is often reduced when applying age-structured stock assessment methods. The integrated approach automatically places more weight on the CPUE data compared to the catch-at-age data, and may therefore provide an alternative to arbitrarily downweighting catch-at-age data.