The promises and pitfalls of including decadal-scale climate forcing of recruitment in groundfish stock assessment

Abstract

Concurrent declines in demersal fish stock abundances and shifts in long-term average environmental conditions have been well documented in the Pacific. Management advice ignoring environmental forcing of recruitment may cause stocks to be over- or under-harvested, so it is important to consider including environmental forcing on recruitment in stock assessment models. Simulation testing is used to determine the statistical power of stock assessments to identify long-term, decadal-scale environmental forcing of recruitment and the ability to estimate management reference points when the duration of the fisheries time series is equal to or less than the period of the environmental cycle. Commonly used assessment methods generally lead to lower total type I (incorrectly rejecting the null hypothesis of no environmental impact) and type II (failing to detect an environmental impact when such a relationship exists) error rates. The promise of integrating environmental data with decadal-scale variability directly into stock assessments via the stock–recruitment relationship is outweighed by the pitfall of high type I error rates that are due to fishing-induced stock declines that coincide with directional environmental change. However, the impact of type I errors can be minimized by choosing an appropriate combination of assessment method and reference point estimators.