Virus strikes lake trout in Warren hatchery
Written by Pittsburgh Post-Gazette   
Wednesday, 28 September 2005 12:12
Almost 1 million trout and eggs will be lost from the Allegheny National Fish Hatchery in Warren after fish there tested positive for an untreatable, contagious virus.

About 620,000 of the infected fish are lake trout, destined for stocking Lake Erie and Lake Ontario next spring in a continuing effort to restore the lakes' trout population.

The rest of the infected fish are rainbow and brook trout being raised for the Pennsylvania Fish and Boat Commission to stock state waterways near the Allegheny National Forest.

A recent tissue sample from the hatchery revealed Infectious Pancreatic Necrosis, or IPN. Though it poses no threat to humans who consume infected fish, IPN does have up to a 90 percent mortality rate in young fish. Those that don't die from it become lifetime carriers and can infect other fish and their own eggs.

"It leads to massive mortality when they're in the fry stage," said Tracy Copeland, the hatchery manager. Fish are in the fry stage at 30 to 60 days old, and about 1 to 2 inches in size.

Most of the lake trout at the hatchery are fingerlings, about 4 to 5 inches long, that hatched in January. They were due to be released next spring.

Now, experts with the U.S. Fish and Wildlife Service, which runs the hatchery, must find a way to depopulate it.

"We're working on the best way to get rid of these fish," Copeland said.

Because of the infectious nature of the virus, they cannot be released into the Great Lakes basin.

One suggestion is to release them into other, already IPN-positive waters, which include many waterways throughout Pennsylvania.

Tom Cochran, southern regional hatchery manager for the state Fish and Boat Commission, said he was unsure if Pennsylvania would be able to take any of the infected fish.

"It's not a decision you can make in the spur of the moment," he said.

Seven of Pennsylvania's eight hatcheries are positive for IPN, Cochran said. But that doesn't mean the state can take those fish from the national facility. Much of the decision will be based on capacity, and whether there is any shortage of lake trout in Pennsylvania, Cochran said.

In addition to the lake trout that will be lost at the hatchery, the facility also will lose its 2,500 brood stock that are responsible for the hundreds of thousands of eggs hatched there each year, as well as 230,000 lake trout eggs.

IPN is a fairly common virus across the world in the trout and salmon families, said John Coll, project leader at the Fish and Wildlife Service's Lamar Fish Health Center in Clinton County.

"In some cases, it's there naturally, and the fish have co-evolved with it," Coll said.

It can be transmitted to fish in a number of ways. At the hatchery, which is at the base of the Kinzua Dam along the Allegheny River, the suspicion is that it was transmitted through the feces of mallards and seagulls, Coll said. Though they are covered by awnings, the 40 raceways for the fish are open on the sides, and easily accessible.

Copeland hopes to have the depopulation plan in place by the end of October and then have the facility decontaminated within 30 to 60 days after that. Disinfecting the hatchery is relatively simple, Coll said, by emptying the ponds, and then soaking them with a chlorine solution for a day.

Before repopulating the facility, Copeland said, they will put full covers over the raceways to avoid future contamination.

She couldn't give a monetary estimate on the loss of the fish but did say the total operating budget for the facility, including salaries, is about $400,000.

"We're not talking millions of dollars spent to raise these fish," she said.

The hatchery in Warren -- one of 69 operated by the federal Fish and Wildlife Service across the country -- is the only one in the United States that stocks lake trout for Lakes Erie and Ontario.

"There will be some loss felt in the Great Lakes due to not being able to catch fish," Copeland said.

But some who run charters on Erie and Ontario say they're not terribly worried about the hatchery's losses.

Clyde Keck, who operates Fantasy Charters out of Fair Haven, N.Y., said in about 80 trips this year, his customers caught maybe 10 lake trout. Typically, while fishing Lake Ontario, they look for brown trout in the spring and salmon during the rest of the season.

Lake trout tend to be oily and less tasty, and they are found on the lake bottom, making them harder to catch. The fish grow to about 15 to 20 inches in length and weigh an average of 10 pounds.

Though Copeland says she does know fishermen who go out and specifically target lake trout, that's not why the hatchery dedicates so much effort to that particular fish.

"The primary goal of this station is to restore the species for Lake Ontario and Lake Erie," she said.

The lake trout was just about wiped out in the 1940s and early 1950s, primarily from the sea lamprey, a primitive fish that latches onto its prey and sucks the fluids out of it, killing it, Copeland said.

The role of the hatchery, which opened in 1974, is to help lake trout become a self-sustaining and self-reproducing fish in the two lower Great Lakes.

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