Relating Marine Mammal Distribution to Prey Abundance

Marine mammal foraging and diet in southern New England is not well known and has therefore been largely ignored as a component of habitat, distribution, and bycatch. Incorporating prey components into marine mammal management is key to improving management of these species, especially as fisheries management progresses towards ecosystem-based management, climate change results in shifting distributions of marine mammals, and we are faced with new management challenges stemming from offshore wind development. This dissertation aims to address data gaps for species highly impacted by human activities, specifically the North Atlantic right whale (Eubalaena glacialis) and the harbor porpoise (Phocoena phocoena), and a suite of species along the continental shelf break that may be subject to future offshore energy development. The first chapter assesses harbor porpoise diet in southern New England, an area of recently increased bycatch where no diet information was previously available. The results of this study could be incorporated into ecosystem-based management, assess likely shifts in habitat due to climate changes, and inform future bycatch management regulations. For this study we examined stomach contents from 46 bycaught harbor porpoises collected over 24 years (1994-2017) between January and May on the continental shelf south of New England. Clupeids, true hakes (Urophycis), cephalopods, and silver hake (Merluccius bilinearis) constituted 85.5% of all estimated biomass, while cusk eels (Ophidiidea) and small flatfish (Pleuronectiformes) were frequently consumed (found in 29.8% and 27.7% of all stomach samples), but each made up less than 1% of estimated biomass due to their small size. Porpoises were found to preferentially select their prey by size and species, overlapping little with gillnet catch, and average prey size was larger for larger porpoise, females, and during the first half of our study (1994-2006 compared to 2007-2017). The second chapter invest