Passive acoustic monitoring off Vancouver Island reveals extensive use by at-risk Resident killer whale (Orcinus orca) populations

A Riera,JF Pilkington,NR Chapman,JKB Ford,EH Stredulinsky

doi:10.3354/esr00966

Abstract

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 39:221-234 (2019) - DOI: https://doi.org/10.3354/esr00966 Passive acoustic monitoring off Vancouver Island reveals extensive use by at-risk Resident killer whale (Orcinus orca) populations Amalis Riera1,*, James F. Pilkington2, John K. B. Ford2, Eva H. Stredulinsky2, N. Ross Chapman1 1University of Victoria, School of Earth and Ocean Sciences, Bob Wright Centre A405, 3800 Finnerty Rd, Victoria, British Columbia V8P5C2, Canada 2Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia V9T 6N7, Canada *Corresponding author: ariera@uvic.ca ABSTRACT: Two sympatric populations of fish-eating Resident killer whales inhabit the coastal waters of British Columbia, Canada: Southern and Northern Resident killer whales. These populations are listed under Canada’s Species at Risk Act (SARA) as ‘endangered’ and ‘threatened’, respectively. Relatively little is known about their habitat use outside of the sheltered waters along the east coast of Vancouver Island, especially during the winter. SARA requires the identification of critical habitat for these populations. High densities of Chinook salmon—their primary prey—are found around Swiftsure Bank, an area identified as potential critical habitat for Southern Residents. However, it is a difficult area to survey for whales using conventional small-boat approaches. Here, we used 2 yr of data collected from an autonomous acoustic recorder deployed at Swiftsure Bank from 2009-2011 to assess the year-round habitat use of this area by Resident killer whales. Overall, Resident killer whales were detected on 244 of 680 monitored days (36%). Southern Residents were heard in all months, with activity peaking during the summer. Northern Residents were also heard throughout the year, but were mostly detected in the spring and fall, which indicates the 2 populations may differ in their strategies for using this common foraging area. High levels of use by both of these populations highlights the importance of Swiftsure Bank to both, supporting the expansion of Resident killer whale critical habitat to include this site. KEY WORDS: Killer whales · Resident · Critical habitat · Passive acoustic monitoring Full text in pdf format PreviousNextCite this article as: Riera A, Pilkington JF, Ford JKB, Stredulinsky EH, Chapman NR (2019) Passive acoustic monitoring off Vancouver Island reveals extensive use by at-risk Resident killer whale (Orcinus orca) populations. Endang Species Res 39:221-234. https://doi.org/10.3354/esr00966 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 39. Online publication date: July 11, 2019 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2019 Inter-Research.

Highlights

Determining patterns in cetacean habitat use is challenging
We investigated the frequency of use and seasonal occurrence of Resident killer whales at Swiftsure Bank off the coast of BC, using long-term passive acoustic monitoring (PAM)
From 1 August 2009−31 July 2011, Resident killer whales were detected on a total of 244 d at Swiftsure Bank (Figs. 2 & 3): Southern Residents on 163 d (24% of recorded days), and Northern Residents on 95 d (14% of recorded days)

Summary

Introduction

Often occurring over expansive ranges in which their movements are generally difficult to predict (Mate et al 1997, Wells et al 1999, Isojunno et al 2012) This challenge is amplified for rarely observed or cryptic species (Rayment et al 2011). Data on habitat use, such as seasonal distribution and movement patterns, can be used to address fundamental questions that are important for conservation management of at-risk populations (Williams & Thomas 2009, Embling et al 2010, Santora & Brown 2010, Becker et al 2012). These fundamental questions include identification of critical habitat (Schorr et al 2009, Williams et al 2009, Baird et al 2012), estimation of seasonal variability in diet (Anderwald et al 2012), evaluation of the influence of environmental factors (Marubini et al 2009, Dalla Rosa et al 2012), assessment of anthropogenic threats (Mate et al 1997), and identification of association patterns, such as habitat sharing and interactions between sympatric populations (Parra 2006, Baird et al 2010).

Methods

Results

Conclusion