Research Document - 2009/015

An Assessment of the Potential for Recovery of Humpback Whales off the Pacific Coast of Canada

By J.K.B. Ford, A.L. Rambeau, R.M. Abernethy, M.D. Boogaards, L.M. Nichol, and L.D. Spaven

Abstract

Humpback whales off Canada’s Pacific coast are listed as Threatened under the Species-at-Risk Act. A draft Recovery Strategy for this humpback whale population is being prepared by DFO in 2008, but insufficient information has been available to set quantitative recovery goals in that document. Here, we present an assessment of recovery potential of Pacific humpback whales in Canadian waters to provide a basis for on-going recovery planning for this population. For this assessment, we used an archive of photo-identifications of individual humpback whales collected during 1992-2006 to estimate population abundance and trends using capture-recapture techniques. These analyses indicate that the humpback whale population has grown rapidly since the beginning of this time series at an estimated annual rate of 4.1% (95% confidence limits, 3.9-5.1%) due to recruitment and a high survival rate of 97.6% (96.0-99.2%). This population growth rate is consistent with recent estimates for the North Pacific population as a whole. The best estimate of abundance for humpback whales in British Columbia waters is 2145 whales (1970-2331) in 2006.; This is still considerably fewer than the minimum of 4000 animals estimated to have existed off the west coast of Vancouver Island in 1905, before large-scale whaling commenced. Current threats to survival and recovery of this humpback whale population include vessel strikes, entanglement in fishing gear, increasing underwater noise, and prey limitation. None of these threats appears to be affecting the population’s growth rate. A Potential Biological Removal (PBR) of 21 animals/year is calculated for this population for allowable harm assessment purposes.

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