Report of the International Whaling Commission (1997)


This report provides harbor porpoise bycatch estimates for 1994 and 1995. The analysis required adjusting for changes in data collection methods that went into effect in June 1994, in which the existing dockside interview system was replaced by a self-reporting logbook system. During the subsequent transition, landings could not be matched directly to statistical area and thus harbor porpoise bycatch during the second half of 1994 and all of 1995 was estimated using a port stratification as compared to a statistical area stratification as was used in previous years. Total harbor porpoise bycatch estimates for the US New England multispecies sink gillnet fishery for 1994 and 1995 were 2,100 (CV= 19%, 95% CI= 1,400-2,900) and 1,400 (CV= 27%, 95% CI= 900-2,500), respectively. To test whether the port stratification analysis method produced results comparable to the previous statistical area method, previous years data (1992 and 1993) were substituted into the port stratification method. The two stratification schemes produced comparable results when applied to the same datasets. To reduce harbor porpoise bycatch, starting in 1994, the New England Fisheries Management Council implemented area and season closures. These closures may have reduced the bycatch in 1995, but the harbor porpoise bycatch levels still remain high, and further reductions are required to reduce the bycatch below Potential Biological Removal as mandated by the US Marine Mammal Protection Act.