(Orcinus Orca) Off the West Coast of Canada
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C S A S S C C S Canadian Science Advisory Secretariat Secrétariat canadien de consultation scientifique Research Document 2012/155 Document de recherche 2012/155 Pacific Region Région du Pacifique Information in Support of the Renseignements à l'appui de la Identification of Critical Habitat for désignation de l'habitat essentiel des Transient Killer Whales (Orcinus orca) épaulards migrateurs (Orcinus orca) au off the West Coast of Canada large de la côte Ouest canadienne John K.B. Ford Eva H. Stredulinsky Jared R. Towers Graeme M. Ellis Fisheries and Oceans Canada, Pacific Biological Station 3190 Hammond Bay Road, Nanaimo, BC V9T 6N7 Canada This series documents the scientific basis for the La présente série documente les fondements evaluation of aquatic resources and ecosystems in scientifiques des évaluations des ressources et Canada. As such, it addresses the issues of the des écosystèmes aquatiques du Canada. Elle day in the time frames required and the traite des problèmes courants selon les documents it contains are not intended as échéanciers dictés. Les documents qu’elle definitive statements on the subjects addressed contient ne doivent pas être considérés comme but rather as progress reports on ongoing des énoncés définitifs sur les sujets traités, mais investigations. plutôt comme des rapports d’étape sur les études en cours. Research documents are produced in the official Les documents de recherche sont publiés dans language in which they are provided to the la langue officielle utilisée dans le manuscrit Secretariat. envoyé au Secrétariat. This document is available on the Internet at: Ce document est disponible sur l’Internet à: http://www.dfo-mpo.gc.ca/csas-sccs/ ISSN 1919-5044 © Her Majesty the Queen in Right of Canada, 2013 © Sa Majesté la Reine du Chef du Canada, 2013 TABLE OF CONTENTS ABSTRACT ............................................................................................................................................................. III RÉSUMÉ ................................................................................................................................................................ IV INTRODUCTION ..................................................................................................................................................... 1 BACKGROUND: LIFE HISTORY, SOCIAL STRUCTURE AND ECOLOGY OF KILLER WHALES ........................................... 1 METHODS .............................................................................................................................................................. 3 PHOTO-IDENTIFICATION STUDIES ............................................................................................................................. 3 PREDATION ANALYSES .............................................................................................................................................. 4 SPATIAL ANALYSES .................................................................................................................................................... 4 MOVEMENT/RESIGHT ANALYSES .............................................................................................................................. 4 RESULTS AND DISCUSSION..................................................................................................................................... 5 DATASET USED FOR HABITAT ASSESSMENT.............................................................................................................. 5 ABUNDANCE AND DISTRIBUTION ............................................................................................................................. 6 LARGE-SCALE MOVEMENTS AND SITE FIDELITY ........................................................................................................ 8 DISTRIBUTION AND LARGE-SCALE MOVEMENTS RELATED TO PREDATION ............................................................. 9 SMALL-SCALE PATTERNS OF HABITAT USE .............................................................................................................. 11 CRITICAL HABITAT: BIOPHYSICAL FUNCTIONS, FEATURES AND THEIR ATTRIBUTES .............................................. 12 IDENTIFICATION OF HABITAT NECESSARY TO MEET RECOVERY OBJECTIVES ......................................................... 13 ACTIVITIES LIKELY TO RESULT IN THE DESTRUCTION OF CRITICAL HABITAT........................................................... 14 Reduction in Prey Abundance or Availability ...................................................................................................... 14 Oil Spills ............................................................................................................................................................... 14 Industrial Developments in Confined Passages ................................................................................................... 15 Environmental Contaminants ............................................................................................................................. 15 Acoustic Disturbance from Human Activities ...................................................................................................... 16 Physical Disturbance ........................................................................................................................................... 16 ACKNOWLEDGEMENTS ........................................................................................................................................ 17 LITERATURE CITED ............................................................................................................................................... 17 TABLES ................................................................................................................................................................. 22 FIGURES ............................................................................................................................................................... 25 ii Correct citation for this publication: Ford, J.K.B, E.H. Stredulinsky, J.R. Towers and G.M. Ellis. 2013. Information in Support of the Identification of Critical Habitat for Transient Killer Whales (Orcinus orca) off the West Coast of Canada. DFO Can. Sci. Advis. Sec. Res. Doc. 2012/155. iv + 46 p. ABSTRACT Mammal-eating transient killer whales off Canada’s Pacific coast are listed as Threatened under the Species-at-Risk Act. A Recovery Strategy for transient killer whales was prepared by DFO in 2007, but insufficient information was available to identify critical habitat in that document. Here we present an assessment of the habitat use and requirements of West Coast Transient (WCT) killer whales in order to provide the basis for the identification of critical habitat for this population. For this assessment, we used an archive of photo-identifications of individual WCT whales collected during 3582 encounters between 1958 and 2011. Based on frequency of occurrence and distribution, we defined two putative subpopulations, a well-known inner coast subpopulation and an outer coast subpopulation that remains poorly known. The inner coast population was composed of 304 individuals identified during 2988 encounters between 1990 and 2011, and this dataset was used to analyse movement and habitat use patterns. The outer coast subpopulation comprised 217 individuals that were rarely encountered. These whales were found in deeper water, further from land, and closer to the continental shelf break than inner coast whales. WCT killer whales are highly mobile and range over the entire BC coast throughout the year. They forage for marine mammal prey in all marine habitats, primarily in close proximity to coastlines. We describe the biophysical functions, features, and attributes of this habitat, most of which involve feeding and adequate abundance and distribution of prey. Based on existing information, we suggest that a habitat area that includes Pacific coast marine waters up to 3 nautical miles (5.56 km) from shore is of sufficient extent to provide for the population and distribution objectives described in this population’s Recovery Strategy, at least for the inner coast subpopulation. This area encompasses the locations of over 90% of all individual identifications and predation events documented with the inner coast WCT subpopulation since 1990. It also includes 64% of identifications of the outer coast subpopulation. This area comprises 40,358 square km, or about 8.9% of Canadian waters off the west coast. Examples of activities likely to destroy critical habitat are described. iii RÉSUMÉ Les épaulards migrateurs qui se nourrissent de mammifères au large de la côte canadienne du Pacifique figurent sur la liste des espèces menacées en vertu de la Loi sur les espèces en péril. Un programme de rétablissement pour les épaulards migrateurs a été préparé par Pêches et Océans Canada en 2007, mais le Ministère ne disposait pas de renseignements suffisants pour désigner l'habitat essentiel dans ce document. Nous présentons ici une évaluation de l'utilisation et des exigences liées à l'habitat des épaulards migrateurs de la côte Ouest afin de poser les jalons de la désignation de l'habitat essentiel pour cette population. Pour cette évaluation, nous avons utilisé des archives de photo-identifications d'épaulards migrateurs individuels recueillies au cours de 3 582 rencontres entre 1958 et 2011. D'après la fréquence