- The Washington Times - Thursday, August 3, 2006

MILLINGTON, Md. — American eels are crafty fish, able to slither up rocks and around branches in just a tiny bit of water.

But it turns out they’re not the strongest swimmers — and dams throughout the Chesapeake Bay watershed may be blocking their natural migration patterns and contributing to a sharp population decline.

Maryland biologists are hoping to boost the fortunes of the American eel, which is found across the Atlantic Coast but is most abundant in the Chesapeake and its tributaries.

Even in the Chesapeake, though, eels aren’t doing so great. Scientists think they’re being stymied in part by dams, which stop eels from coming upstream as juveniles from the ocean and spending most of their lives in freshwater tributaries.

The effect of dams on fish has long been acknowledged, and 16 of Maryland’s 1,000 dams have been modified to allow fish to pass through so they can spawn.

Problem is, biologists in recent years have concluded that what works for fish such as shad or herring doesn’t work for eels.

Eels prefer slower-moving water, migrating at night along the sides of rivers, and because they’re only about 4 inches long when they head upstream, few of them can power their way through traditional fish passages.

“They can’t swim in really heavy currents. They’re looking for slow water,” said Steve Minkkinen, a biologist with the U.S. Fish & Wildlife Service Maryland Fishery Resource Office.

Mr. Minkkinen and four other state biologists built a passageway just for eels Tuesday on a 10-foot-high dam at Unicorn Lake in Queen Anne’s County.

The eelway is the first built in Maryland, though they’re common in New England.

It’s a pretty low-tech device. Mr. Minkkinen took a length of black plastic pipe often placed under roads. Plastic netting was glued to the bottom — eels need something to crawl on for traction, not the metal sides of a fish passage — and a trickle of water was pumped down it, enough to keep the netting wet but not so much that the juvenile eels would be swept away.

The tube was screwed together and placed on top of an existing fish chute with a faster water flow, with the top dumping into the lake.

Eelways cost about $2,000 for small dams — much less than some fish passages — and biologists hope they’ll open more habitat to American eels.

The eel population decline is dire.

Though about 50 Maryland watermen still make a living off eels, catching 300,000 pounds last year for sale to restaurants abroad, the population is thought to be far below historical levels.

Mr. Minkkinen said that before the Conowingo Dam was built in 1928, watermen in New York’s Finger Lakes region harvested a million pounds of eels a year. Now the entire eel population north of the dam has vanished, he said.

“Coastwide, eelers have declined because the population has declined,” said Keith Whiteford, a biologist for Maryland’s Department of Natural Resources.

It’s not known exactly how far down the America eel population is.

However, the national eel harvest was less than a million pounds last year; in the mid-1970s, catches were about 3.5 million pounds.

The U.S. Fish & Wildlife Service is considering naming the American eel an endangered species, though a final determination isn’t due until later this summer.

Dams aren’t likely the sole cause of the decline, said Steve Gephardt, an eel specialist at the Connecticut Department of Environmental Protection.

Mr. Gephardt advises the Atlantic States Marine Fisheries Commission on the American eel and said the era of widespread dam-building is over, so something else must be playing a role in the recent decline of eels.

But building eelways on dams is still a good idea, Mr. Gephardt said.

“We know over time that dams have decreased the number of eels,” he said. “They can wiggle around a lot of stuff, they can do a lot of tricks, but, in fact, they don’t swim that well. So you have to think like an eel, and the fishways we were building weren’t doing that.”

The fisheries commission estimated that 84 percent of upstream habitat has become unreachable for eels.

It probably will take years for the eelways to help. The fish don’t reach sexual maturity for eight to 24 years, and they spawn only once, according to the commission, so detriments in the population can take decades to become apparent.

Mr. Minkkinen hopes low-tech assistance such as a plastic pipe and a slow trickle of water can help turn around the population of a species most people don’t like because of its snakelike appearance.

He pointed out that eels are important food sources for other fish and birds of prey, plus they play a role in mussel reproduction because mussel larvae attach to eels.

In rivers that no longer have eels, the mussels are gone, too.

“It’s a species that hasn’t been considered much, unfortunately,” he said. “But they’re important ecologically. Right now eels can’t get into a lot of their habitat, so let’s open up as much habitat to them as possible.”

LOAD COMMENTS ()

 

Click to Read More

Click to Hide