Recruitment forecast models for walleye pollock Theragra chalcogramma fine-tuned from juvenile survey data, predator abundance and environmental phase shifts

Abstract

Forecasting recruitment of marine fishes from environmental effects acting upon larvae has proven difficult due to multiple, nonlinear, interacting factors influencing larval survival. We used another approach, which circumvents the period of high egg and larval mortality, and instead improves forecasts from juvenile abundance indices. We compared several statistical recruitment forecast models and demonstrate that an increasing abundance of predators on juvenile walleye pollock Theragra chalcogramma, particularly the arrowtooth flounder Atheresthes stomias, which now dominates the groundfish biomass in the Gulf of Alaska, and autocorrelation caused by intercohort interactions strongly affect pollock recruitment during the juvenile phase. Furthermore, the weight of predictor variables changes with threshold criteria, which are linked to phase shifts in the marine environment. Our results indicate that forecasting recruitment of marine fishes can be improved by considering factors that influence survival after the juvenile period, but also needs to account for changes in community structure and phase shifts in the environment, as opposed to only environmental correlates. Inclusion of these factors is consonant with biological knowledge of the species. © Inter-Research 2010.