Research Technical Report

Fish Community Shifts Driven by Marine Heatwaves Aren’t Mitigated by MPAs

Freedman, R.M., J. Brown, C. Caldow, and J. Caselle (November 2020)

Oral presentation at the Western Society of Naturalists Annual Meeting, November 5-8, 2020, Virtual Meeting

ABSTRACT

Efficiently quantifying ecological shifts from acute climate events is challenging, leading to a disconnect between real-time community composition and management action. Our study classified thermal affinities of kelp forest fish species using biogeographic data and expert opinion to create a simplified method to track differential responses to climatic events. We used this newly developed classification scheme to track the response of multiple fish community metrics to a marine heatwave that occurred off the US West Coast. Density and recruitment of ‘warm species’ were significantly higher during the marine heatwave (2014-2017) compared with years prior (2002- 2013). ‘Cold species' did not experience significant parallel declines. Marine Protected Areas (MPAs) did not appear to buffer these community shifts as responses were similar both inside and outside MPAs. Non-fished species were more responsive to environmental drivers compared to targeted species which means managers looking to preserve ecosystem structure in response to acute climate disturbance should utilize additional conservation strategies.