Tope (Galeorhinus galeus) COSEWIC assessment and status report: chapter 9

Limiting Factors and Threats

The intensive fishery for tope between 1937 and 1949 throughout their migratory range in the northeast Pacific would have caused a rapid depletion in the adult biomass resulting in the collapse of the fishery (Walker 1999; Ebert 2003). Since that time tope have not received any commercial or research attention aside from reported landings by state fisheries departments and incidental catch in Canadian fisheries. An ongoing, unreported recreational fishery occurs off California (Ebert 2001). A clear limitation to understanding the status of this species is the lack of information.

The degree to which the stock has recovered or remained depressed since the 1940s is unknown. Walker (1999) argues that although the fishery collapsed during the 1940s, it is unlikely the stock collapsed. He argues that sharks targeted during this brief period were mainly of a relatively large size and because the small juveniles, which would take several years to recruit to the fishery, were only lightly fished it is likely the stocks should have recovered after fishing ceased. However, it is unknown whether unreported recreational fishing and small amounts of commercial fishing since the 1950s have impeded recovery. Since the 1940s there has not been any major incentive to target tope in the northeast Pacific. Other sharks such as the thresher shark (Alopias vulpinus) and shortfin mako (Isurus oxyrinchus) are more valuable in the marketplace and easier to capture than tope (Walker 1999). Canadian catch and mortality is unknown but likely less than 3t/yr. U.S. catch is presently approximately 21 t/yr for a combined estimated northeast Pacific removal of 24 t/yr.

In the seven years between 1938 and 1944 approximately 15,600 t of tope may have been removed from waters along the west coast of North America. This catch can be used as a surrogate for a minimum historic population. Present-day population biomass and recovery level are unknown.

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