Development of conservation strategies to mitigate the bycatch of harbor porpoises in the Gulf of Maine

Abstract

In this paper I review the development of conservation strategies to address the bycatch of harbor porpoises Phocoena phocoena in Gulf of Maine gillnet fisheries from 1982, when bycatches were first detected, until a Take Reduction Plan was implemented in 1999. After consideration of several mitigation options, the plan included a combination of time-area closures and the use of acoustic alarms. Implementation of these measures reduced the annual bycatch of porpoises from a high of 2900 in 1990 to 323 in 1999, the first year in which bycatches fell below the potential biological removal (PBR) level. The success of these measures can be attributed to several factors, including a clear conservation goal, the PBR level, mandated by the US Marine Mammal Protection Act. The importance of PBR is underscored by contrasting experiences in the USA, where the goal was achieved, and those in Canada, where no comparable goal existed and no conservation measures were implemented. The availability of detailed scientific information on bycatch levels and abundance was critical to persuading all stakeholders of the need to act. Successful negotiation within the Take Reduction Team was facilitated by a long prior history of informal collaboration and dialogue. Finally, the monitoring program provided important feedback on the efficacy of measures in reducing bycatch, effectively closing the loop on the management process. This case study is instructive in several regards with respect to the elements necessary to address bycatch issues involving small cetaceans and gillnet fisheries.