Bluntnose sixgill shark (Hexanchus griseus) COSEWIC assessment and status report: chapter 9
Limiting Factors and Threats
Fishing presents the only known proximate threat to bluntnose sixgill shark populations in Canada. This species is caught regularly by hook and line gear types and to a lesser degree by trawl gear. While the actual catch is not accurately known, two estimates of the catch in hook and line gear, derived from observer data using different methods are 12 tons per year (t/yr) and 38 t/yr for the 2001 to 2004 time period. Captured fish are likely primarily immature animals (see section Interactions with Fisheries). Between 1996 and 2005, catches in the commercial trawl fisheries have averaged about 1.1 t/yr. The degree to which this amount of catch is impacting the population as a whole is unknown. Dunbrack and Zielinski (in press) demonstrated that of 35 sharks observed one third bore scars consistent with fishing gear interaction. None of the seven sharks larger than 280 centimetres bore scars suggesting that larger animals either do not interact or are more able to break free without damage.
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