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We know how to catch ’em, but that’s about it

Ann Barse, PhD., associate professor in the department of biological sciences at Salisbury University, and her assistants exam a white marlin at Harbour Island Marina during the 39th annual White Marlin Open last year. (Lisa Capitelli)

(Aug. 2, 2013) Hundreds of anglers will arrive in Ocean City next week hoping to land a prize-winning fish in the 40th annual White Marlin Open tournament. Last year, almost 1,000 white marlin were released during the weeklong event and anglers seeking marlin, tuna, wahoo, shark and dolphin netted around $2.3 million in prize money.

But little is actually known about the lives of the tournament’s namesake fish.

“For as much as we know about the fishing of these animals, the biology of these animals is pretty vague,” said John Graves, chair of the fisheries department at the Virginia Institute of Marine Science.

White marlin start their lives somewhere near the Sargasso Sea. Though researchers track them, they can swim well over 100 miles in a day, making pinpointing exact breeding grounds as yet unfeasible, Graves said.

Traveling that far takes a lot of fuel, making marlin voracious eaters.

“You’ve seen that hot dog eating contest on Coney Island? These fish would put those guys to shame,” Graves said. He’s pulled more than 20 market-sized squid from the stomach of a 50-pound marlin.

The fish grow quickly — up to four feet in the first year of their lives, Graves said. They likely reach maturity quickly, too, at around two or three years old, but aging marlin has also proved difficult. That’s because scientists use their spine fins to age them based on the number of rings they see, but after about age two, those rings disappear.

Scientists do know that marlin can live around 20 years based on tagging projects, Graves said.

Marlin migrate as far north as the Grand Banks in Newfoundland in the summer and retreat south or into the Atlantic Ocean’s core during colder months. Because they cross international lines, management of the fishery must also be at the international level, Graves said.

White marlin stocks are around 15 percent of the virgin population — 50-80 percent below the number that would maximize their productivity, Graves said.

“We have seen a big decrease in the abundance of these animals,” he said. As far as managing the fishery, “unless countries are doing this in concert, it’s going to have very little impact on the resource.”

That’s partly why a failed petition from the Center for Biological Diversity to get white marlin added to the U.S. list of endangered or threatened species would have been a scant management tool, Graves said.

Another reason is that stocks simply aren’t that low, said Ann Barse, a biology professor as Salisbury University. Barse and her students have taken samples from fish landed at the White Marlin Open on an off for 15 years.

“The numbers now look better than they did before,” Barse said.

A National Marine Fisheries Services law requiring U.S. anglers to use circle hooks in place of standard J hooks has helped marlin stocks, she said. The hooks tend to catch marlin in the corner of their mouths, rather than lodging in deep tissues, where they can cause more damage, Graves explained.

In a study, six out of 20 fish died after being caught with J hooks and released, Graves said. In contrast, his team found that 100 percent of the marlin tracked survived past 10 days when caught with a circle hook and released.

The commercial fishery also plays a role in determining marlin stocks, though. Those fisheries don’t target white marlin, but often catch them alongside tuna and other target species on their long lines.

“It has probably had a pretty big effect on these animals,” Graves said.

The United States has pushed for an international measure requiring marlin caught as bycatch on long lines to be released, which could have a big impact since more than 50 percent of those marlin are still alive when they’re pulled, Graves said.

On a local scale, marline stocks seem to be growing, but weather has played a roll in numbers so far this year, Graves said.

“They haven’t been as abundant in the catches yet this year” because the cool spring pushed the season back, he said, but warm currents could bring more of the fish for the tournament.

Graves expects that it will be a good year for bigeye tuna at the tournament.

“Lots of people fish for white marlin just because it’s very exciting,” Barse said. “It’s the excitement of the crowd and the competition” that draw thousands of anglers to the annual tournament.

“They’re absolutely beautiful, so their biology fascinates people,” she said.

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