Scientists report that young scallops off the eastern seaboard have been struggling to grow to maturity for nearly a decade now, constraining one of the nation’s most lucrative fisheries to its lowest biomass in more than 20 years.

In a presentation before the New England Fishery Management Council on Wednesday, the council’s scallop analyst Jonathon Peros projected that the latest regulations adopted by the council will cap next year’s scallop harvest at 25 million pounds — a steep drop from a record harvest of 61 million pounds recorded just four years earlier.

Still, the projections are higher than a historic lull the scallop fishery experienced in the late 1990s, according to data collected by the National Oceanic and Atmospheric Administration. The fishery’s subsequent recovery followed a decision to close and monitor fertile scallop grounds and is now touted by NOAA as a “fishery success story.”

But the forces limiting the growth of young scallops in recent years pose a new mystery to fishermen and scientists alike. Some researchers suspect warming waters and ocean acidification play a role by weakening scallop shells; others blame an influx of predators that are eating larval scallops before their shells have a chance to harden.

Federal and academic scientists supported by the scallop industry are still testing a range of hypotheses, but regulators on Wednesday had to accept a degree of uncertainty in order to keep pace with an ever-changing ocean.

“The 2022 surveys showed some of the cyclical nature of the fishery,” Peros said in an interview after his presentation.

What’s certain, he said, is the latest surveys found young scallops in places where spawning had lagged for nearly a decade. Peros said the council plans to close some of those areas to fishermen for at least two years in an effort to help the scallops grow and spawn again before they are harvested.

“Billions of small animals were detected there,” Peros said, “and that's a real bright spot for this fishery.”

Fortunately, for commercial fishermen, a lean year for scallops can sometimes correspond with a surge in their price. Just last year, American fishermen hauled in one of the lighter Atlantic scallop harvests of the past 20 years. But their scallops fetched record prices, pushing the fishery’s revenues to an all-time high of $671 million, according to a NOAA database tracking seafood landings in state and federal waters.

Most of that revenue flows through New Bedford, the nation’s most lucrative fishing port, where scallop landings account for more than 80 percent of the port’s seafood revenue.

The fishing industry provides about 6,000 jobs in New Bedford, a crucial source of employment in a city of 100,000 people that ranks among the poorest communities in Massachusetts.

Eric Hansen, a fisheries council member who owns two New Bedford-based scallop boats, said he is not alarmed about the long-term health of the port’s most important fishery.

But protecting growing scallop beds will require a financial sacrifice that he said could be difficult for boat owners who are expanding their operations or just breaking into the industry. As for deckhands, mates and captains, it's almost certain there will be less work next year in the scallop fishery.

“Whether it will be painful, that remains to be seen what happens with the price,” Hansen said.

Ben Berke is the South Coast Bureau Reporter for The Public’s Radio. He can be reached at Follow him on Twitter @BenBerke6.