The number of shad migrating up the Susquehanna River in Maryland has fallen by almost half over the past year, part of a worrisome decline up and down the East Coast, scientists say.
The drop means that counts of American shad at Conowingo Dam have fallen by more than 90 percent over the past seven years. That is a stark reversal from the 1990s, when the construction of fish lifts at dams - and bans on shad fishing - spurred a revival of what has been called "the founding fish" because of its dominance as a food in Colonial times.
Researchers count the shad in April and May as they swim through a fish elevator that allows them to pass over a dam in Harford County to go upstream to spawn.
Because of the decline here and elsewhere, the Atlantic States Marine Fisheries Commission is planning public hearings on whether more restrictions should be imposed on catching American shad, officials said. Fishing for the species is banned in Maryland and Pennsylvania, but not in New Jersey, Delaware, New York, North Carolina and other states.
"We've seen decreases in American shad at fish lifts all along the East Coast, suggesting it's not just at the Conowingo Dam," said Erica Robbins, fisheries management plan coordinator at the commission.
The shad's rise and fall has created a twist to an environmental success story. Populations of rockfish, or striped bass, in the Chesapeake Bay and its tributaries surged after a ban on catching them. But the bass eat shad. And as the bass have multiplied, they seem to be gobbling up the shad, said Dilip Mathur, a fisheries biologist who has run the annual shad count at Conowingo Dam for decades.
"The striped bass are taking a good chunk of the American shad," said Mathur, an environmental consultant for Exelon Corp., which owns the hydroelectric dam. "There wasn't really a large population of striped bass until 10 or 15 years ago, and since then the population has exploded - and now the organisms are trying to reach a balance."
But pollution and excessive fishing also are likely factors, scientists said.
American shad are silvery fish with rows of darks spots along their sides. They grow to about 2 feet and are oily and bony but famously tasty - especially their eggs, or roe.
Until nets stretched across rivers nearly wiped out the species in the 19th and early 20th centuries, shad was among the most popular dishes in the Chesapeake region.
In the spring, shad swarm up rivers and streams all along the Atlantic Coast to spawn. After laying their eggs, the adults return to the ocean and spend the summer feeding on plankton off the coasts of Maine and Canada.
Issue with striped bass
Striped bass grow to three times the size of shad and eat just about anything. Like shad, they were nearly eliminated by overfishing, but a ban on catching them in Maryland and elsewhere in the late 1980s helped their numbers rebound, according to the state Department of Natural Resources.
Dale Weinrich, manager of the finfish program at the agency, said the rising numbers of striped bass, catfish and other predators probably are eating American shad.
But he said that's only part of the picture - and he doubts that's the main reason for the shad's recent drop. He noted that shad and bass coexisted in abundance for thousands of years before people messed up the ecological balance with pollution, dams and overfishing.
A more recent factor in the shad decline might be excessive fishing for them in the Atlantic Ocean, Weinrich suggested.
Despite a ban on targeting shad by fishing boats in many U.S. states, he said he suspects that fishermen off Canada or elsewhere in the Atlantic might be netting too many shad.
"Someone is perhaps targeting the shad for fishing," said Weinrich. Or fishermen pursuing other species might be catching shad in their nets accidentally, he said. "But once you get them in a net, they're dead."
Robbins, of the marine fisheries commission, concurred that striped bass are probably playing a role in the falling shad numbers, along with other factors, including water pollution, development and dams.
Conowingo fish lift
The fish lift at Conowingo Dam was built at a cost of $15 million more than a decade ago, after the U.S. Fish and Wildlife Service sued the dam's owners for blocking the shad's migration upriver. At first, it worked well.
The number of fish lifted over the dam by an elevator-like mechanism rose from 37,516 in 1996 to 193,574 in 2001.
But since then, it has been falling, to 56,000 in 2006, 29,000 last year, and about 16,000 so far this year, according to the federal agency and the dam's operators.
Fishermen along the base of the dam said Friday that they've noted the decline. But they said a less tasty kind of shad - called hickory shad, which are smaller and darker - remain plentiful.
By Maryland law, fishermen can't keep hickory or American shad, but they can catch and release them.
Travis Habecker, 29, a cabinetmaker, cast his line near the Conowingo Dam's roaring, frothing outfalls Friday morning. Not far away, cormorants bobbed in the powerful brownish current.
Standing on a pile of boulders, Habecker got a bite, then reeled in a footlong shad.
The morning sun flashed off its silvery flanks as he wrestled with the fish, removed the hook and tossed it back into the swirling current.
He said he caught and released about 50 American shad (which local fishermen call "white shad") during the migration this spring, compared with about 100 last year.
He thinks it's true that striped bass - "stripers" - are devouring shad because he's seen it happen.
"A lot of times, you're catching a shad and trying to reel it in - and a striper will just come up and eat it before you can even land it," Habecker said. "The bass are so large, they take the shad with them and go. The line goes 'buzz!' and runs out and then snaps. And they're gone."