Thursday, September 23, 2010

Ooooooooh, Barracuda

Vancouver Sun: Secrets of barracudas revealed in thesis

Ottawa's Amanda O'Toole swam with barracudas to help determine where and how they live, Tom Spears reports.

Everyone in the Caribbean knows the barracuda, a big, tough predator that watches curiously from a short distance away when humans snorkel or dive around coral reefs.

Yet the big fish is a mystery. Does it swim long distances or stay at home? Where does it spawn? If you catch and release one, does it survive?

Carleton University student Amanda O'Toole of Ottawa found almost no one had studied the barracuda except for one guy from Miami in the 1960s. That's unusual for a top predator in any ecosystem. People study lions, tigers, grizzlies. Why not barracudas?

So off she went to study the fish for her master's thesis in biology.

It fit nicely with O'Toole's interests:

Enjoys working outdoors. Check.

Likes conservation. Check.

Likes to travel to the Bahamas in winter. Definitely.

"They're a very common fish," she says. That's one reason to study them; often scientists only get around to studying animals once they're endangered, leaving questions about what a healthy population looks like.

To conserve a species, you have to know where and how it lives, says O'Toole's adviser, Carleton professor Steven Cooke.

"When we started working on them, we were blown away" by the knowledge gap, he says.

O'Toole swam with her barracuda, feeling no fear. Attacks on humans are rare and usually seem to occur when the diver is carrying something that looks like a fish, she believes.

"They're fun to photograph. They're just really cool fish."

The barracuda is important both to the ecosystem and for sport fishing. Often they're caught by accident by someone looking for mahi mahi or other sport fish, but some people also try to catch barracuda.

That led to one question: Does a barracuda that's released recover? Mostly yes, she found. "They're quite robust" but they still have to be treated gently to avoid injury.

"These areas are quite predator-heavy, so there are lots of sharks or other barracuda around, ready to chomp a vulnerable fish as you release it."

She also studied a common toxin that some fish absorb called ciguatera, which can poison humans. The question was whether fish in one area carry more toxin than fish from a few kilometres away.

Yes, the local residents say.

No, her results showed, because the barracuda loves to travel.

"We put tags inside of barracuda. We have all these little listening stations set up on the ocean floor" near the island of Eleuthera, and these devices recorded where the fish moved.

Some stayed in one spot, but others moved around freely. "Our little telemetry array spans about 14 kilometres square, and sometimes these fish will zip straight across it in a day."

One even swam from her area to another fish-monitoring base 100 kilometres away, and back.

Some mysteries remain, though. The fish disappear for months in the summer, presumably leaving the continental shelf for the deep regions lying nearby. They may be spawning.

O'Toole has just finished her master's and moved to Vancouver, where she'll work for a consulting firm that studies the effects of development on fish.

She's happy to be working with fish, "but I'll miss my barracuda."

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