Cetacean occurrence in the Gulf of Alaska from long-term passive acoustic monitoring

Ally Rice,Amanda J Debich,Ana Širović,Jennifer S Trickey,John A Hildebrand,Rachel S Gottlieb,Sean M Wiggins,Simone Baumann-Pickering

doi:10.1007/s00227-021-03884-1

Abstract

The Gulf of Alaska is an important habitat for a diverse array of marine mammals, many of which were severely depleted by historical whaling. To study current cetacean distributions in this region, passive acoustic monitoring was used to detect species-specific call types between 2011 and 2015 at five locations spanning the continental shelf, slope, and offshore seamounts. Spatial and temporal detection patterns were examined for nine species to compare differences in behavior and habitat use. Mysticetes showed seasonal increases in calling that indicated possible behavioral shifts between feeding and breeding in blue (Balaenoptera musculus), fin (B. physalus), and humpback (Megaptera novaeangliae) whales, and matched known migration timing of gray whales (Eschrichtius robustus). Interannual changes in blue and fin whale calling may relate to the marine heat wave that began in 2013 and lasted through the end of the monitoring period. Odontocete detections revealed unique spatial distributions, with killer whales (Orcinus orca) most common on the continental shelf and sperm whales (Physeter macrocephalus) most common on the continental slope, where detections occurred year-round. Beaked whales showed both spatial and temporal separation: Baird’s beaked whale (Berardius bairdii) detections were highest at Quinn Seamount in the spring, Cuvier’s (Ziphius cavirostris) at Pratt Seamount in winter, and Stejneger’s (Mesoplodon stejnegeri) on the continental slope in the fall. The year-round presence of many species highlights the ecological importance of the Gulf of Alaska and the spatiotemporal information reported here should inform future conservation efforts.

Highlights

The Gulf of Alaska (GoA) is a North Pacific region composed of a variety of habitats, all of which are important to a diverse array of marine mammal species
Blue whales (Balaenoptera musculus) are currently considered endangered under the Endangered Species Act (ESA) and have only occasionally been sighted in the GoA in recent years (Zerbini et al 2006; Calambokidis et al 2009; Rone et al 2017), but passive acoustic monitoring efforts indicate that blue whales from both the Northeast Pacific (NEP) and Central/Western Pacific (CWP) populations inhabit this region for at least a portion of the year (Stafford et al 2001, 2007; Stafford 2003; Zerbini et al 2006; Rone et al 2017)
Blue whale CenPac and D calls, fin whale 40-Hz calls, and gray whale M3 calls were more prevalent in the spring and summer and blue whale B calls, fin whale 20-Hz calls, and humpback whale calls were more prevalent during the fall and winter (Fig. 4)

Summary

Introduction

The Gulf of Alaska (GoA) is a North Pacific region composed of a variety of habitats (a shallow continental shelf region, a steep shelf break, deep offshore waters, and deepwater seamounts), all of which are important to a diverse array of marine mammal species. This region is considered a highly productive marine ecosystem due to its subarctic. Blue whales (Balaenoptera musculus) are currently considered endangered under the Endangered Species Act (ESA) and have only occasionally been sighted in the GoA in recent years (Zerbini et al 2006; Calambokidis et al 2009; Rone et al 2017), but passive acoustic monitoring efforts indicate that blue whales from both the Northeast Pacific (NEP) and Central/Western Pacific (CWP) populations inhabit this region for at least a portion of the year (Stafford et al 2001, 2007; Stafford 2003; Zerbini et al 2006; Rone et al 2017)

Objectives

Methods

Results

Discussion

Conclusion