Shortfin mako (Isurus oxyrinchus) COSEWIC assessment and status report: chapter 4

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Distribution

Global range

Shortfin makos are distributed circumglobally in all tropical and temperate seas (Figure 4). There are no data indicating that their global range has changed. Compagno (2001) describes shortfin mako range in the northwestern Atlantic as being from the Gulf of Maine to Bermuda.

Canadian range

Atlantic Coast

In Canadian waters the shortfin mako is typically associated with warm waters such as in and around the Gulf Stream. It has been recorded from Georges and Browns Bank, along the continental shelf of Nova Scotia, the Grand Banks and even into the Gulf of St. Lawrence (Templeman 1963). Observer data from Canadian, Faroese, and Japanese vessels indicate that makos are caught both in inshore waters and offshore waters between 39º-50ºN (Figure 5). This species is a highly migratory seasonal visitor (late summer and fall) to Canada’s Atlantic coast. The population in Canadian waters represents the northern extension of the North Atlantic-wide population and likely only represents a small portion of the total population. There are no data to indicate either an expansion or reduction in shortfin mako range within Atlantic Canadian waters.

Pacific Coast

Compagno (2001) describes the range in the central Pacific as being from south of the Aleutian Islands to the Society Islands, and the Hawaiian Islands and in the eastern Pacific from Washington State to central Chile. There has been only one confirmed shortfin mako caught in Canada’s Pacific waters (360 km due west of Cape St. James) (Gillespie and Saunders 1994). Shortfin makos are probably only occasional visitors to Canada’s Pacific waters during periods of higher than normal ocean temperatures. The lack of confirmed records in Pacific Canadian waters indicates that they are either rare in those waters and/or do not overlap with human activities. Databases searched include the International Halibut Commission survey data, PacTrawl, GFBio, all DFO groundfish survey reports, and National Marine Fisheries Service Triennial Survey.

Pelagic longlining is the primary fishing gear responsible for the bycatch of shortfin mako sharks worldwide. Presently in Canada’s Pacific waters, this type of fishing practice does not exist, whereas on Canada’s Atlantic coast this practice is very common. The absence of records from Canada’s Pacific waters may reflect the absence of pelagic longline fishing methods and not the absence of this species. However, there are regular records of other large pelagic sharks (e.g. blue shark) in other gears in Canada’s Pacific, so most likely the shortfin mako is genuinely rare and vagrant.

Because of the single record, this species does not meet COSEWIC’s criteria for eligibility for assessment – it can be considered a vagrant in Canadian waters. Accordingly this status report does not provide further information on shortfin mako in Canada’s Pacific waters.