Pacific herring, Clupea pallasi, recruitment in the Bering Sea and north-east Pacific Ocean, II: relationships to environmental variables and implications for forecasting

Previous studies have shown that Pacific herring populations in the Bering Sea and north-east Pacific Ocean can be grouped based on similar recruitmen t time series. The scale of these groups suggests large-scale influence on recruitment fluctuations from the environment. Recruitment time series from 14 populations were analysed to determine links to various environmental v ariables and to develop recruitment forecasting models using a Ricker-type environmentally dependent spawner-recruit model. The environmental variable s used for this investigation included monthly time series of the following : southern oscillation index, North Pacific pressure index, sea surface tem peratures, air temperatures, coastal upwelling indices, Bering Sea wind, Be ring Sea ice cover, and Bering Sea bottom temperatures. Exploratory correla tion analysis was used for focusing the time period examined for each envir onmental variable. Candidate models for forecasting herring recruitment wer e selected by the ordinary and recent cross-validation prediction errors. R esults indicated that forecasting models using air and sea surface temperat ure data lagged to the year of spawning generally produced the best forecas ting models. Multiple environmental variables showed marked improvements in prediction over single-environmental-variable model.