Disentangling conditional effects of multiple regime shifts on Atlantic cod productivity.

• Published in: PLOS ONE
• Main Authors: Tommi Perälä, Esben M Olsen, Jeffrey A Hutchings
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science (PLoS) 2020
• Subjects: Medicine; R; Science; Q; atlantic cod; North Atlantic; North Atlantic oscillation
• Online Access: https://doi.org/10.1371/journal.pone.0237414; https://doaj.org/article/3e7a865dc4244117a32fbd77e084e831

Regime shifts are increasingly prevalent in the ecological literature. However, definitions vary and detection methods are still developing. Here, we employ a novel statistical algorithm based on the Bayesian online change-point detection framework to simultaneously identify shifts in the mean and (or) variance of time series data. We detected multiple regime shifts in long-term (59-154 years) patterns of coastal Norwegian Atlantic cod (>70% decline) and putative drivers of cod productivity: North Atlantic Oscillation (NAO); sea-surface temperature; zooplankton abundance; fishing mortality (F). The consequences of an environmental or climate-related regime shift on cod productivity are accentuated when regime shifts coincide, fishing mortality is high, and populations are small. The analyses suggest that increasing F increasingly sensitized cod in the mid 1970s and late 1990s to regime shifts in NAO, zooplankton abundance, and water temperature. Our work underscores the necessity of accounting for human-induced mortality in regime shift analyses of marine ecosystems.