Environmental indicators to reduce loggerhead turtle bycatch offshore of Southern California

Miss Heather Welch1

1University of California Santa Cruz / NOAA, Monterey, United States

Extreme climatic events are expected to become more frequent under current conditions of increasing global temperatures and climate variability. A key challenge of fisheries management is understanding and planning for the effect of anomalous oceanic conditions on the distributions of protected species and their interactions with fishing gear. Environmental indicators can serve as early warning signals that allow for proactive management responses before significant bycatch occurs. Marine heatwaves in the Pacific have caused shifts in the distributions of endangered loggerhead turtles (Caretta caretta), increasing overlap with California’s Drift Gillnet fishery and thereby the risk of turtle bycatch events. To reduce bycatch, a fishery closure offshore of Southern California is enacted when an El Niño event has been declared. However, this regulation was based on qualitative assessment of a limited bycatch dataset. Providing a quantitative indicator could help to refine future decisions. Our objectives were to: 1) develop a suite of thermal indicators, and 2) hindcast closure scenarios based on these indicators to evaluate efficacy in terms of opportunity costs to fishers and turtle interaction avoidance. The best indicator was a SST anomaly derived indicator with closures enacted above a threshold of 0.77 °C. This result can improve upon the current closure guidelines by providing a quantified and spatially-explicit indicator. Our analysis seeks to demonstrate the feasibility of the explicit incorporation of an environmental metric into fisheries regulation, thereby aiding a movement towards fisheries management strategies that are responsive to climate variability and change.


Heather Welch’s research focuses on understanding and planning for the spatial and temporal dynamics of large-scale marine processes, including climate variability and change.

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