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Recovery Strategy for the Basking Shark (Cetorhinus maximus) in Canadian Pacific Waters [Final Version]

Executive Summary

The Pacific population of Basking Shark (Cetorhinus maximus) was assessed as ‘endangered’ in 2007 by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). In February 2010 the population was listed as ‘endangered’ under Canada’s Species at Risk Act (SARA), affording it legal protection. 

The Basking Shark is the world’s second largest fish, reaching a maximum recorded length of 12.2 metres. They are filter-feeders, feeding primarily on zooplankton. Basking Sharks are found circumglobally in temperate coastal shelf waters. In Canadian Pacific waters, they are considered to be part of a North American population which migrates into British Columbia waters in spring and summer and winters off California (McFarlane et al. 2009). Current abundance in Canadian Pacific waters is unknown, but it is estimated that some proportion up to the full range-wide population (321-535 individuals) utilizes Canadian Pacific waters on a seasonal, annual, and decadal scale (McFarlane et al. 2009). Historically, large aggregations of Basking Sharks were seasonally common and widely distributed in Canadian Pacific waters (COSEWIC 2007). At present, Basking Sharks appear infrequently in Canadian Pacific waters with only 13 confirmed sightings since 1996.

The key factors limiting the recovery and survival of Basking Sharks are their long-life (~50 years), slow growth and maturation, and low fecundity which lead to overall low productivity. Even in the absence of human-induced mortality, Basking Shark populations grow very slowly. The Pacific population of Basking Shark is threatened by various anthropogenic sources. Four classes of current threats have been identified in this Recovery Strategy, which are entanglement, collision with vessels, harassment from marine based activities, and prey availability. The decline of the Pacific population of Basking Shark is primarily due to human-caused mortality which occurred between 40 and 70 years ago. Broad strategies and approaches to address the limitations and threats are presented in this recovery strategy.

The following population and distribution objectives will guide recovery efforts for Basking Sharks within Canadian Pacific waters:

  1. Maintain the current abundance of Basking Sharks.
  2. Attain positive population growth of Basking Sharks within 15-20 years.
  3. Attain increase in Basking Shark aggregations (two or more sharks).
  4. Maintain distribution of Basking Sharks within the northern extent of their historical distribution range.

Adequate information does not exist to identify critical habitat at this time. Habitat requirements have not been investigated for Basking Sharks in Canadian Pacific waters, and no specific locations have been identified for reproduction, pupping or rearing. Thus, a schedule of studies has been included in this document, which outlines the research required to gather information that will contribute to the future identification of critical habitat. It is important to note that it may take decades to address the issue of identifying critical habitat, given the long lived nature of the species, a lack of documented recent sightings in Canada, and the associated long-term scope of this recovery strategy. An action plan will be completed within five years of final posting of the Recovery Strategy.