Diet of harbor porpoises (Phocoena phocoena) on the continental shelf off southern New England

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Little is known about the diet of harbor porpoises (Phocoena phocoena) in southern New England Where bycatch Was a highly contentious issue since the late 1990s until recently. To fill this data gap, stomach contents Were examined from 46 harbor porpoises taken as bycatch over 24 years (1994–2017) between January and May. Prey species Were identified to the lowest possible taxon through hard part analysis, primarily of otoliths and squid beaks. Size and species of harbor porpoise prey overlapped little With those of gillnet catch. Average prey size Was larger for adult harbor porpoises (≥140 cm total length), females, and those taken during the first half of our study (1994–2006) than for smaller porpoises, males, and those caught during the second half (2007–2017). Average total biomass consumed per stomach Was 2.3 kg, an estimate that represents approximately 12–24 h of feeding. Clupeids, true hakes (Urophycis spp.), squids (Decapodiformes), and silver hake (Merluccius bilinearis) constituted 85.5% of all estimated biomass. Cusk-eels (Ophidiidae) and small flatfish species (Pleuronectiformes) Were frequently consumed (found in 29.8% and 27.7% of all stomach samples), but each taxon made up less than 1% of estimated biomass because of their small size. These results could help advance ecosystem-based management by better defining the diet of harbor porpoises in the context of potential climate changes.

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Fishery Bulletin