Column by DFO's Ian Marshall
When most people think of sharks, they think of dangerous predators. However, this perception is, for the most part, incorrect. Most sharks are not dangerous to humans.
This is fortunate for us as many sharks live in the waters off Canada’s Atlantic coast. Actually, there are about 14 different species known to frequent this area – common types include the spiny dogfish, blue shark and porbeagle shark. The porbeagle shark, not considered to be a threat to humans, is one of the most commonly seen sharks in this area. It is estimated that 80 per cent of the North American population of 180,000 porbeagle sharks reside in eastern Canadian waters.
Porbeagle sharks are blue-grey with white underneath and are quite large, growing up to almost three metres long. They prefer to spend most of their time deep down in cooler water, where few other fish are caught. Porbeagle sharks are at the top of the food chain, and consequently, play a crucial role in maintaining the health of their ecosystem. This species is carefully managed under the Fisheries Act and in collaboration with the fishing industry and stakeholders to ensure its protection and recovery.
Over the past decade, a decline in the porbeagle shark population has resulted in focused Fisheries and Oceans Canada (DFO) research on this species and conservation measures to ensure the population is not only sustained, but allowed to recover. Recently, there has been an exciting discovery – a new breeding ground for porbeagle sharks on Georges Bank, which lies in the Gulf of Maine between Nova Scotia and the United States.
Following up on reports from fish harvesters, DFO scientists, in co-operation with the shark fishing industry, conducted an exploratory fishing charter for porbeagle sharks on Georges Bank in 2008. Each shark that was captured was lively and in excellent condition, and was handled gently for examination; a saltwater hose was placed in its mouth to allow it to breathe and a wet cloth was placed over its eyes to reduce its stress. Each shark was satellite tagged and returned to the water to swim away. These special tags track the shark’s movement, swimming depth and the temperature of the water – helping improve our knowledge of porbeagle sharks and their migration patterns.
This charter confirmed that large female porbeagle sharks are gathering on Georges Bank for breeding. Prior to this discovery there was only one known breeding ground for porbeagles in the northwest Atlantic, off the coast of southern Newfoundland and in the southern portion of the Gulf of St. Lawrence. Two breeding grounds means good news for the prospects of recovery of the health of the population, as it is not reliant on just one area for reproduction. This gives renewed hope for maintaining a healthy population for the species.
DFO has played an important role in porbeagle shark research and conservation. In conjunction with the shark fishing industry, DFO scientists and fishery managers are ensuring that the porbeagle shark population doesn’t decline, and recovers to a healthy level.
Should funds become available, DFO in collaboration with the Atlantic Shark Association will conduct the second portion of a 2007 shark survey to confirm population numbers and recovery.
For more information please visit: http://www.marinebiodiversity.ca/shark/english/porbeagle.htm (Ian Marshall is the DFO Area Director for Southwest Nova Scotia. If you would you like to read about other DFO issues that affect you and your community in future columns send en email to CommEnquire@mar.dfo-mpo.gc.ca or call (902) 426-3550.)