Evaluating the efficacy of environmental legislation: A case study from the US marine mammal Take Reduction Planning process

There have been limited efforts to evaluate the efficacy of environmental management programs, in part because environmental legislation often lacks objective, quantifiable criteria to use in such assessments. Here we evaluate the ecological outcomes of an important element of one well-known environmental statute, the US Marine Mammal Protection Act (MMPA), using take reduction planning as a case study. Take reduction planning is mandated by the MMPA as a means to reduce mortality of marine mammals in US fisheries to below statutory thresholds. We used data from formal Stock Assessment Reports to assess and rank the success of five Take Reduction Plans (Harbor Porpoise, Bottlenose Dolphin, Atlantic Large Whale, Pelagic Longline, and Pacific Offshore Cetacean) in mitigating the bycatch of 15 marine mammal stocks. In general, Take Reduction Plans have had an uneven record of meeting their statutory requirements. Successful plans were characterized by straightforward regulations and high rates of compliance. Unsuccessful plans covered marine mammal–fisheries interactions in the northeastern US, had low compliance with complex regulations and sometimes focused on very small stocks. This study emphasizes the importance of requiring legally mandated, quantitative metrics and long-term monitoring programs to evaluate the efficacy of a well-known element of an established environmental management program.