Incremental fishing gear modifications fail to significantly reduce large whale serious injury rates

Abstract

A major and immediate goal of the US Marine Mammal Protection Act is the reduc- tion of marine mammal mortality incidental with commercial fishing operations. Under articles of the Act, the Atlantic Large Whale Take Reduction Plan (ALWTRP) was developed and imple- mented to reduce entanglement mortality of North Atlantic right whales Eubalaena glacialis, Gulf of Maine humpback whales Megaptera novaeangliae, and western North Atlantic fin whales Bal- aenoptera physalus by requiring modifications to commercial fishing gear (i.e. pots and sink gill- nets). Although they undercount the number of entanglements, counts of detected incidents of entanglements and entanglement-related mortality are the primary index to entanglement mor- tality. We analyzed the annual counts of large whale entanglements including serious injuries and mortalities attributed to entanglements to evaluate the effectiveness of the ALWTRP from 1999 to 2009. The annual number of mortality events (including serious injuries) related to fishing gear entanglements averaged 2.5 for right whales, 6.5 for humpbacks, 0.6 for fin whales, and 2.4 for minke whales B. acutorostrata. Annual entanglement rates increased during the study period, but evidence for increased rates of entanglement-related mortality was equivocal. No significant changes occurred in waiting time (the number of days between entanglement events) in response to any management measures implemented to reduce large whale mortalities between 1998 and 2009, implying that these measures were generally ineffective in abating whale deaths from entanglements in fishing gear.