Risk of lethal vessel strikes to humpback and fin whales off the west coast of Vancouver Island, Canada

Bm Wright,Jkb Ford,P O’Hara,Lm Nichol

doi:10.3354/esr00813

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 32:373-390 (2017) - DOI: https://doi.org/10.3354/esr00813 Risk of lethal vessel strikes to humpback and fin whales off the west coast of Vancouver Island, Canada Linda M. Nichol1,*, Brianna M. Wright1, Patrick O’Hara2,3, John K. B. Ford1 1Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia V9T 6N7, Canada 2Institute of Ocean Sciences, Canadian Wildlife Service, Environment Canada, Sidney, British Columbia V8L 4B2, Canada 3Department of Biology, University of Victoria, Victoria, British Columbia V8W 3N5, Canada *Corresponding author: linda.nichol@dfo-mpo.gc.ca ABSTRACT: Vessel strikes are a source of mortality and injury for baleen whales, which can have population-level impacts. Spatial analysis of whale and marine traffic distributions provides a valuable approach for identifying zones with high collision risk. We conducted 34 systematic aerial surveys to estimate humpback Megaptera novaeangliae and fin whale Balaenoptera physalus densities off the west coast of Vancouver Island, Canada, including approaches to major shipping lanes in Juan de Fuca Strait, a gateway to the ports of southern British Columbia and Washington State. To predict whale densities, we fit negative binomial generalized additive models (GAMs) to sightings data, incorporating survey effort as an offset, and depth, slope, and latitude as environmental covariates. Humpbacks were primarily observed on the continental shelf, with highest predicted densities along the shelf edge (~200 m isobath), whereas fin whales were primarily distributed west of the shelf break (>450 m depth). We combined GAM-predicted whale densities with vessel traffic data to estimate the relative risk of ship strikes. Since vessel speed is an important determinant of lethality, we also calculated the relative risk of lethal injuries, given the probability that a collision occurs. Humpbacks were most likely to be struck along the shelf edge, the inshore approaches to Juan de Fuca Strait, and within the strait itself. Fin whales were most likely to be struck in the offshore approaches to Juan de Fuca and inside the western portion of the strait. Our study is the first to assess ship strike risk in this region of high whale density and marine traffic use. KEY WORDS: Vessel strike · Ship speed · Lethal injury · Humpback whale · Fin whale · Generalized additive model · Distance sampling · Spatial distribution · Spatial density model Full text in pdf format PreviousNextCite this article as: Nichol LM, Wright BM, O’Hara P, Ford JKB (2017) Risk of lethal vessel strikes to humpback and fin whales off the west coast of Vancouver Island, Canada. Endang Species Res 32:373-390. https://doi.org/10.3354/esr00813 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 32. Online publication date: May 04, 2017 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2017 Inter-Research.

Highlights

Vessel strikes, or collisions between ships and cetaceans, are a key threat to the recovery of baleen whale populations in many areas of the world, including Canadian Pacific waters (Fisheries and Oceans Canada 2013a,b)
After filtering for weather conditions, effort status, and altitude, 276 of the 322 total baleen whale sightings with distances less than the truncation distance (2650 m) remained. This included a total of 159 humpback whale or ‘like humpback whale’ sightings (329 ind.), and 74 fin whale or ‘like fin whale’ sightings (120 ind.; Fig. 2), which were input into the generalized additive models (GAMs) following the exclusion of a single outlier in the humpback sighting data
Ship strike risk analysis based on spatial models of whale density provided an effective approach for identifying regions of conservation concern, in areas where actual mortality rates are difficult to quantify from carcass evidence or eye-witness reports

Summary

Introduction

Collisions between ships and cetaceans, are a key threat to the recovery of baleen whale populations in many areas of the world, including Canadian Pacific waters (Fisheries and Oceans Canada 2013a,b). Humpback Megaptera novaeangliae and fin whale Balaenoptera physalus populations in British Columbia (BC) are listed as ‘Special concern’ and ‘Threatened’, respectively, under Canada’s Species at Risk Act (COSEWIC 2015). Both populations have been undergoing recovery after severe depletion by commercial whaling, which ended in the Canadian Pacific in 1967 (Ford 2014). Humpback whales were the most commonly reported species involved in vessel collisions, with an individual reported injured or killed approximately every 9 mo They were the most frequently observed species bearing healed or partially healed wounds indicative of vessel collision injuries They were the most frequently observed species bearing healed or partially healed wounds indicative of vessel collision injuries (Fisheries and Oceans Canada unpubl. data)

Methods

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Discussion

Conclusion