Tracking one of Nova Scotia's top predators

- August 6, 2013

Students and OTN researchers prepare a blue shark to be tracked. (Bruce Bottomley photo)
Students and OTN researchers prepare a blue shark to be tracked. (Bruce Bottomley photo)

If you've ever been off Nova Scotia's coast and spotting a fast-moving shark fin in the water, the first image that leapt to mind might have been the ominous namesake of Jaws — or, perhaps something more like the ridiculous, airborne threats from the recent TV B-movie Sharknado.

But while Great Whites do occasionally show up in our waters, chances are what you saw was probably a blue shark, one of the more common species of shark in our region.

Named for the hue of their skin, and averaging about 2-3 metres in length, blue sharks can be found in temperate and tropical waters surrounding every continent except Antarctica. But though it's one of Nova Scotia's top ocean predators, it's also among the least understood, as little information is available on the behaviours of Canadian blue shark populations.

The Dal-hosted Ocean Tracking Network (OTN) is working to change this. Last week, energy company Encana announced a donation of $50.8K from its Deep Panuke Education & Training and Research & Development for OTN to study blue sharks off the coast of Nova Scotia and to train students in the capture, tagging and tracking of marine animals.

Encana is the owner and operator of the Deep Panuke natural gas project in Nova Scotia’s offshore. The goal of the two-year project is to better understand blue shark population — their feeding habits, their migrations — to limit human impact on their activities.

"Tagging juveniles could help us locate a nursery in the region and figure out if the nursing ground and behaviours are being unintentionally affected by human activity," said Brendal Davis, biologist for the shark tagging component of the grant.

Shark tagging in action

Last Wednesday, a crew of Dalhousie students and OTN researchers hit the seas bright and early in the morning, travelling 17 km off the coast of Sambro Island. They were joined by Dal President Richard Florizone and a crew of media representatives on-hand to observe the tagging of six blue sharks as part of the project.

Using a mixture of fish and squid as chum, the team hooked its first blue shark after about 30 minutes. Hauled onto the boat, the researchers placed the shark on its back, using a hose to keep salt water in the shark's mouth (so it can flow over its gills). The team then made a small incision, placing an acoustic tracker inside the sharks body before quickly stitching up the wound and setting the shark free.

The team repeated the same process — about 10 minutes in total — for five more sharks. The goal is to tag 40 sharks over the project's two years. The sharks will be tracked using a network of acoustic receivers that will be expanded by new receivers placed on Encana's offshore oil and gas infrastructure.  

"If we are to maintain the health of ocean ecosystems, we have got to take care of the top predators," says OTN Executive Director Fred Whorisky. "The unique partnership of this project is enabling research that will help us understand the needs of these animals, and ensure a future for them."

Video: Shark tagging off Nova Scotia's coast


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