Breaking down a barrier for fish

Dam blocked 20 miles of Octoraro Creek for about a century


Steel-jawed machines ripped apart a century-old stone dam on a stream near the Susquehanna River yesterday, which will enable blue-backed herring and hickory shad to swim to their spawning grounds.

The demolition of the Octoraro Creek Dam will help struggling species, including American eel, travel into a 20-mile section of the tributary that has been blocked for about 100 years, said David Sutherland, a biologist with the U.S. Fish and Wildlife Service.

As part of a national effort to remove river blockages that have almost wiped out several varieties of fish, the Maryland Department of Natural Resources has worked with federal agencies to demolish about a dozen dams since 1989, the last in 2000.

"Ecologically, the habitat loss has taken a great toll on fish, and about one-third of fish species are now rare or endangered because of dams, overfishing and water-quality problems," Sutherland said, as the backhoe chugged through the muddy waters to clear a hole in the 100-foot-long dam.

"We are learning the impact of the thousands of dams that have been built across America -- 75,000 total dams blocking 600,000 miles of rivers in America," Sutherland said.

The man-made pond behind the dam emptied, stranding about 50 fish, flipping and squirming in the algae-painted mud of the drying lake.

Sutherland and a team of volunteers squished through the newly exposed muck in boots, grabbing the gasping fish and saving their lives by tossing them into the opened passage.

The dam was built about 100 years ago for a grain mill long since abandoned in this wooded area of Cecil County, near a Boy Scout camp and gun club.

"This dam was an old, abandoned pile of rocks, not serving any purpose but blocking fish passage up the creek from the Susquehanna," said Serena McClain, a representative of American Rivers, an environmental group. A $25,000 federal grant paid for the demolition.

A side benefit of the project is that canoeists will be able to paddle from the Susquehanna River up the creek to Camp Horseshoe, run by the Boy Scouts about five miles from the dam.

Affected species

Many of the fish that will be helped are shad, a fish that was a mainstay of the region's economy before being almost wiped out by overfishing and the construction of dams in the 19th and early 20th centuries.

Hickory shad, a variety small enough to make it up shallow Octoraro Creek, grow to up to 20 inches long. They have jutting lower jaws and an amber hue that is darker than American shad, which are silvery and torpedo-shaped.

Also aided by the project will be the American eel, whose numbers have declined so much that they are being considered for listing as an endangered species.

These eels, which grow to up to 5 feet long, have an "amazing life cycle," Sutherland said. They are born in the Sargasso Sea, an area of the Atlantic Ocean with enormous rafts of floating weeds legendary for snaring ships.

The larva drift in the ocean for up to a year before metamorphosing into transparent "glass" eels, about 2 1/2 inches long. In the fall, these glass eels migrate into the Chesapeake Bay, changing colors to a yellowish hue and swimming up streams like Octoraro Creek.

Remarkably, the eels can leave the water to slither across dams like worms, said Jim Thompson, a fisheries biologist with the DNR.

Thompson said he saw a 14-inch eel yesterday wiggling across the Octoraro Dam's mossy rocks. But many others have been caught or slowed by the dam. Swarms of them have been gathering downstream from the dam, and this makes them vulnerable to predators such as heron and raccoons, which gobble up the delicacies, Thompson said.

The stranded eels have also been netted by poachers, who sell them to brokers in Asia for sushi and breeding in aquaculture, Thompson said.

Removing the dam will enable the eels to pass swiftly up the river, making them less easy prey, he said.

The eels spend most of their lives, which can span three decades, in streams and rivers, feeding on insects and worms.

"In some ways, dams are harder on eels than they are on fish, because they have to spend their whole lives in a shrunken river habitat," Thompson said.

Fish such as shad have the opposite life cycle, spending most of their lives in the ocean, returning to creeks only to breed.

Just before eels die, they stop eating and undergo a profound physical transformation.

Their eyes bulge to twice their normal size. Their fins grow, skulls change shape, digestive systems shrink, and the males shift colors to gray with a bronze sheen on their sides, gilded by glistening slime.

In their new bodies, the eels journey thousands of miles from streams such as the Octoraro back to their birthplace in the Sargasso Sea, where they breed and then die.

Helping the bay

Nancy Butowski, manager for the DNR's fish passage program, said that opening long-clogged riverways such as the Octoraro Creek is an important part of healing the Chesapeake Bay ecosystem.

"We are hoping this will have a big impact," she said, as she watched water rushing through a breach in the dam. "It will probably be years before we see the fish populations rise here, because it takes years for them to mature and return home. But this is an important part of Chesapeake Bay restoration."

Baltimore Sun Articles
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.