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.
