Jon Atwood, PhD
Department of Environmental Studies
Mortality from incidental entanglement (bycatch) in fishing gear has been shown to negatively affect seabird populations in many regions around the world. However, comparatively little is known about bycatch in the productive commercial fisheries off the New England coast. This thesis reviews 10 years (1994-2003) of seabird bycatch data collected in this region by fisheries observers with the National Marine Fisheries Service (NMFS). I estimate total annual mortality and evaluate the potential impacts of this mortality and evaluate the potential impacts of the mortality on the most affected species. Eighteen species of seabirds were observed caught in fishing gear from five fisheries: sink gillnet, palegic longline, bottom trawl, midwater trawl, and scallop dredge fisheries. The most detailed and consistent observer coverage was for the sink gillnet and pelagic longline fisheries, and my analyses indicate that bycatch rates were highest in these fisheries. I found significant differences in bycatch rates over the study period. I estimated a total of 2225 seabirds were killed each year in the 1994-1999 time period, while 750 were killed each year in the 2000-2003 time period. This decrease may be due to fewer numbers of birds foraging in the region during the later period, when total ocean productivity decreased as a result of the negative phase of the North Atlantic Oscillation ocean circulation system. The seabird species most frequently caught were shearwaters (mainly Greater Shearwaters) and gulls (mainly Great Black-backed Gulls). My analyses indicate that mortality in New England commercial fisheries of these species was low compared to total population size and mortality in other regions. However, the cumulative impact of mortality in fisheries throughout the range of these species remains to be evaluated.