Abstract

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 investigated North Atlantic right whale prey choices on the continental shelf south of New England. Researchers recently found that these highly endangered whales inhabit the continental shelf south of Rhode Island and Massachusetts year round, and are present and feeding in higher numbers during the late winter and early spring. However, little is known about right whale foraging in this region and the factors driving distribution of their prey. During a short research cruise in April of 2018 we opportunistically investigated potential right whale prey choices in southern New England. After spotting two diving right whales in an area with numerous documented sightings in the previous two weeks, we

Highlights

  • Marine mammals are threatened throughout their range by fisheries bycatch (Read et al 2006, Lewison et al 2014, Burgess et al 2018, Gray & Kennelly 2018) and increasingly by climate change (Learmonth et al 2006, Simmonds & Isaac 2007, Sydeman et al 2015)

  • Marine mammal distribution is primarily driven by prey resources for much of the year, with this reliance varying by species and reproductive life history strategies

  • Stomach samples were collected by the Northeast Fisheries Observer Program (NEFOP), part of the National Oceanic and Atmospheric Administration’s (NOAA) National Marine Fisheries Service

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Summary

Introduction

Marine mammals are threatened throughout their range by fisheries bycatch (Read et al 2006, Lewison et al 2014, Burgess et al 2018, Gray & Kennelly 2018) and increasingly by climate change (Learmonth et al 2006, Simmonds & Isaac 2007, Sydeman et al 2015). Right whales occupied northern feeding grounds rich in their primary prey, Calanus finmarchicus copepods, hereafter referred to as C. finmarchicus, from late winter to early autumn These areas included the Great South Channel, Cape Cod Bay, the Bay of Fundy, and Roseway Basin (Kenney et al 2001, Baumgartner & Mate 2005). Recent studies modelling marine mammal coast-wide distributions in both the Atlantic and the Pacific linked data from marine mammal surveys to environmental covariates, most of which represented either ocean surface or ocean floor characteristics (Forney et al 2012, Roberts et al 2016, Becker et al 2019, ChavezRosales et al 2019) These environmental covariates, while proven useful, act as proxies for water-column characteristics such as prey concentrations that define pelagic habitat but are not directly sampled. Until now, this approach has not been applied to large-scale abundance surveys involving numerous species

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