Tuna quick to swim away after catch and release, scientists find

Early results of a new study show catch and release has little impact on tuna.

Gary Melvin, a research scientistwith Fisheries and Oceans Canada, and a team of researchers are catching, tagging, releasing and tracking the mortality and movements ofbluefin tuna throughout the Gulf of St. Lawrence.

Last week, the research team wastagging tuna off ofTignish, P.E.I.

We're hoping to see if there is what we call post-release mortality. At the moment we aren't seeing any evidence of that.- Gary Melvin

"It's always the big question when you hook a fish and they fight, what happens? And it's common thought that they recover and swim away," Melvin said.

But, added Melvin, there is also a concern that exhausted fish sink to the bottom and die.

The early results of his study are that the fish are quick to swim away.

"A lot of the mortality, you would suspect, would occur when they're first released. They're just exhausted and they go and sink to the bottom," he said.

"We have tagged seven fish to date and not one of them went to the bottom."

From the research boat Melvin can track the fish up to 2.5 kilometres away, and the tuna swim away so quickly he can only track them for 10 to 15 minutes.

Dalhousie reports tracked fish

Once out of range of the boat, the tuna is not necessarily lost forever.

Microphone arrays around the Gulf of St. Lawrence, down the eastern seaboard, and even in Europe, are installed to catch the sound of the acoustic tag as the fish pass.

"When the fish goes by one of these acoustic arrays they will be detected," Melvin said.

"When the fish leave the Gulf of St. Lawrence and go out through the Cabot Strait, we should know."

Melvin is hopeful the majority of his tags will be detected again. He is hoping to track the tuna down the coast as they go through the different arrays.

"We're hoping to see if there is what we call post-release mortality. At the moment we aren't seeing any evidence of that," he said.

This week the team plans to tag off of North Lake, P.E.I., and then work out of Antigonish, N.S., the following week.

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