Scientists aren’t sure what’s behind the slump, and many say it worries them because crabs are such an important part of the Bay region’s seafood industry and food culture.
“It’s rough surf,” said Tom Miller, who’s been studying the blue crab, Callinectes sapidus, for nearly three decades. He’s director of the Chesapeake Biological Laboratory at Solomons, MD, part of the University of Maryland Center for Environmental Science.
The Chesapeake’s crab population tends to yo-yo naturally every year or two. This year, though, marks the third below-average tally from the annual winter dredge survey, in which Maryland and Virginia check for crabs waiting out the winter in bottom sediments in 1,500 spots around the Bay and in its rivers.
What’s even more troubling is that the survey’s estimate of juvenile crabs has also hit an all-time low, or nearly so, for two years running. With so few young available to produce the next generation in a species that only survives a couple of years, a quick rebound looks iffy.
Crabs have been in deep trouble before, falling in 1998 into a decade of below-average abundance and subpar harvests.
By 2008, Miller and other scientists thought they’d turned the corner by getting fishery managers to impose harvest limits intended to conserve female crabs so more could spawn. They set an overfishing threshold for females — “sooks,” as crabbers call them — and a target number believed sufficient to rebuild the population and boost harvests.
At the time, it was the best available science, Miller said, “no doubt in my mind about that.”
Now, he’s not so sure.
It appears the fault can’t be laid on crabbers this time. While overfishing female crabs was a problem in the past, the catch has stayed within bounds since 2008. The adult female crab population has been 76% higher on average than it was in the decade before female-oriented harvest limits were set, Miller said.
Yet “recruitment” — the number of young crabs that make it from egg to adult — has not improved. Nor has the harvest grown in the way scientists and managers expected it would. In 2021, the Baywide commercial catch was 36.3 million pounds, well below the long-term average of 60 million pounds.
Miller said one statistic is especially troubling: The average number of young crabs reaching maturity for every spawning-age female has declined by 40% since female-oriented harvest limits were imposed.
“The blue crab stock is less productive than it was previously,” he told the Potomac River Fisheries Commission in June.
Something appears to have changed. Or maybe the experts have missed something. In hindsight, Miller said he’s concerned that they may have aimed too low in deciding how many females are needed to sustain the population.
“I think at one level we have to bear responsibility,” Miller said. With female crab abundance suggesting the stock was sustainable, scientific and management attention focused more in recent years on restoring the Bay’s oyster population. “To an extent,” he added, “we’ve taken our eye off the ball.”
Well, live and learn.
The Wombat has Late Night With Rule 5 Sunday: Olga Alberti out on time.