Challenges of Area Restrictions to Mitigate Interactions with Marine Mammals: A Case Study of the California Drift Gillnet Fishery

The success of area restrictions depends not only on the accuracy of the science underlying the designation of the area, but also external factors that influence compliance with and enforcement of restrictions. Thus protected areas test the willingness of fishermen to modify fishing behavior, often in very productive ocean areas, and the capacity of management to adequately monitor the fishery to make the protected areas successful at reducing marine mammal interactions. For the California drift gillnet fishery the success of the protected area determines whether or not fishing can continue below the Marine Mammal Protection Act’s threshold of “negligible impact” on endangered marine mammals. Following the take of two endangered sperm whales (Physeter macrocephalus) in one gillnet set in 2010, the Fisheries Service issued emergency regulations in September 2013 to require 100% observer coverage in a zone covering nearly all areas in the U.S. EEZ deeper than the 1,100 fathom depth contour and immediate closure if one sperm whale is observed killed or seriously injured. High bycatch rates despite area closures and gear modifications show the limits of mitigation measures and suggest considering wholly different gears that are inherently cleaner (e.g., harpoons) to replace drift gillnets.