Linking Northeast Pacific recruitment synchrony to environmental variability

Abstract

We investigated the hypothesis that synchronous recruitment is due to a shared susceptibility to environmental processes using stock–recruitment residuals for 52 marine fish stocks within three Northeast Pacific large marine ecosystems: the Eastern Bering Sea and Aleutian Islands, Gulf of Alaska, and California Current. There was moderate coherence in exceptionally strong and weak year‐classes and correlations across stocks. Based on evidence of synchrony from these analyses, we used Bayesian hierarchical models to relate recruitment to environmental covariates for groups of stocks that may be similarly influenced by environmental processes based on their life histories. There were consistent relationships among stocks to the covariates, especially within the Gulf of Alaska and California Current. The best Gulf of Alaska model included Northeast Pacific sea surface height as a predictor of recruitment, and was particularly strong for stocks dependent on cross‐shelf transport during the larval phase for recruitment. In the California Current the best‐fit model included San Francisco coastal sea level height as a predictor, with higher recruitment for many stocks corresponding to anomalously high sea level the year before spawning and low sea level the year of spawning. The best Eastern Bering Sea and Aleutian Islands model included several environmental variables as covariates and there was some consistent response across stocks to these variables. Future research may be able to utilize these across‐stock environmental influences, in conjunction with an understanding of ecological processes important across early life history stages, to improve identification of environmental drivers of recruitment.

Somatic growth contributes to population variation in marine fishes

“…Empirical estimates of recruitment (a, c, e) (Stachura et al., ) and growth (b, d, f) variation (Stawitz et al., ) over time, as measured in deviations from mean normalized recruitment and growth for petrale sole, Pacific hake and widow rockfish…”

“…Comparison of recruitment deviations (grey) generated using time series of recruitment variation by a time‐series model to recruitment estimates (Stachura et al., ) (blue) from population models fit to empirical data…”

“…Survival through early life‐history was simulated using the production function producing the best fit (AIC) to the observed MB data and recruitment estimated by Stachura et al. ().…”

Density regulation in Northeast Atlantic fish populations: Density dependence is stronger in recruitment than in somatic growth

“…Besides density‐dependent processes analysed in this study, major drivers of population dynamics are environmental conditions (Borja, Fontan, Sáenz, & Valencia, ; Skagseth, Slotte, Stenevik, & Nash, ; Stachura et al., ), ecological interactions (Huse, Salthaug, & Skogen, ; Skaret, Bachiller, Langøy, & Stenevik, ), additional intraspecific feedbacks (Ricard, Zimmermann, & Heino, ) and fishing (Anderson et al., ). Growth is sensitive to various factors that cause inter‐ and intra‐annual variations, confounding estimation of density dependence.…”

Common trends in recruitment dynamics of north‐east Atlantic fish stocks and their links to environment, ecology and management

“…Identifying synchrony and shared trends among fish stocks could help to determine the key drivers behind ecosystems dynamics and improve the predictability of recruitment (Stachura et al., ). Determining common trends and interactions from data will thus shed some light on the many open questions about recruitment dynamics and contribute to an ecosystem‐based approach to management of fish stocks.…”