Sharks play an essential rol in the health of our oceans

Information, Research

Cool Canadian Porbeagles!

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Porbeagle, picture by Doug Perrine

Direct commercial fishing for the porbeagle shark (Lamna nasus) led to stock collapses in the eastern North Atlantic in the 1950s, and the western North Atlantic in the 1960s. The porbeagle continues to be caught throughout its range, both intentionally and as bycatch, with varying degrees of monitoring and management. The porbeagle shark is Critically Endangered in the Northeast Atlantic and Mediterranean where fisheries are unmanaged. The Mediterranean population has virtually disappeared. It is Endangered in the Northwest Atlantic — female spawning stock has decreased to 12% and 16% of previous levels. In the Southern Ocean it is classed as Near Threatened –depletion of spawning stock indicates biomass is 18% of previous levels. The North Atlantic population has been seriously depleted (~90%) by commercial fisheries for the shark’s high value meat (source:  sharks.org).

Startling migration pattern

The Bedford Institute of Oceanography (Steve Campana et al.) carried out porbeagle research that was not only focused on age and growth, but also on migration movements. It showed some startling results: all of the mature females migrated south to the Sargasso Sea (between Bermuda and Cuba) to give birth to their pups. The migration required the sharks to traverse the Gulf Stream, whose water temperatures are too warm for the cold-water porbeagle. Therefore, the porbeagles literally dove underneath the Gulf Stream to depths of 1360 metres to avoid the warm water. While in the Sargasso Sea, the porbeagles maintained an average depth of almost half a kilometre, which probably explains why they have remained undetected over the years. This research has been published (Campana et al. 2010).    porbeagle-14-eng

Continued research in the Bay of Fundy

 

The research on the sharks in the Bay of Fundy,  a bay between the Canadian provinces New Brunswick and Nova Scotia, will be continued in 2015. The project is lead by Dr. Steve Turnbull (University of New Brunswick – Saint John), Sharks Unlimited – Alma, New Brunswick and St. Andrews Sport Fishing Co. – St. Andrews, New Brunswick, and focuses on Aspects of the Biology of the Porbeagle Shark  in the Bay of Fundy, Canada. Thresher sharks that are caught will also be tagged. . All sharks released are tagged with an ID tag and some with archival satellite popup tags. Results to date indicate a high post-release survival rate for sharks, possible different movement patterns for males and females within the Bay, and a high portion of caught sharks are large females (more info: http://standrewssportfishing.com/2015/01/18/sport-fishing-shark-fishing-bay-fundy-2015/).

 

Porbeagle about to be tagged, picture St. Andrews Sport Fishing Co.

Porbeagle about to be tagged, picture St. Andrews Sport Fishing Co.

 

The International Union for Conservation of Nature (IUCN) has assessed the porbeagle as Vulnerable worldwide, and as either Endangered or Critically Endangered in different parts of its northern range. In the Netherlands, porbeagle fishing and landing is prohibited. The porbeagle is listed on Appendix III of the Convention on International Trade in Endangered Species.

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