Scientists probe sharp drop in Chesapeake Bay’s blue crab population

A new report on the Chesapeake Bay’s signature blue crab has documented a steep, long-term decline in the crustacean’s population, raising concerns among environmental groups about the future of one of the region’s most important species.

Scientists aren’t sure exactly what’s behind the drop. The total number of blue crabs can fluctuate sharply, with population estimates varying by tens of millions – or even hundreds of millions – within just a few years. But experts said they’re concerned by what they’re seeing.

“It’s clear the bay’s most iconic species is under immense stress,” according to the Chesapeake Bay Foundation, which was not involved in the assessment but whose scientists closely monitor its results.

There are numerous ways to gauge crab “abundance,” the term researchers use to denote the overall population or that of different subgroups, such as juveniles. Michael Wilberg, the assessment’s lead author, cited one overarching finding: In 2011, the bay had about 1.3 billion crabs. By 2023, that dropped to about 825 million, he said.

Habitat loss, especially the reduction of underwater grasses that shelter young crabs, may be playing a role, experts said. Changes in currents, winds and storms, pollution and runoff, and low oxygen “dead zones” caused by algae blooms, may all also contribute, experts said.

“They’re a short-lived species and the biggest thing we’re seeing is a decline in the number of young crabs entering the population,” said Chris Moore, the Chesapeake Bay Foundation’s Virginia executive director. “That long-term trend of fewer young ones is very concerning.”

Healthy blue crabs are vital to the bay’s ecosystem. They eat worms, clams and smaller crabs, and are prey for fish, great blue herons and sea turtles. Blue crabs also generate $50 million to $80 million annually for Maryland’s and Virginia’s commercial crabbing industries, experts said.

The assessment is conducted roughly every 10 to 15 years, depending on funding, with the help of environmental research and marine science centers and fishery agencies in Maryland and Virginia. It evaluates the species’ overall health and sustainability, including predator impacts, habitat, mortality rates, harvest levels, and the number of spawning females, and serves as a guide for fishery managers.

The vast number of crabs in the bay in the early 1990s was driven down by overharvesting, experts said. Tighter limits on crabbing helped stabilize the population, but it has since dropped. While some years have seen increases – 2026 was one of them, according to a long-running annual government survey – totals remain far below historic highs.

“We’re still not where we want to be because we’ve been so low,” Wilberg said.

The 290-page assessment helps give a more in-depth sense of what is happening to blue crabs over a longer period than the annual surveys and other reports done by agencies. Moore called it a “guiding light of how we manage the species.”

“We’re seeing a pretty consistent decline in mature female crabs that looks remarkably similar to what we saw in the 1990s,” said Thomas Miller, professor of fisheries science at the University of Maryland Center for Environmental Science. He’s concerned the numbers will stay low.

The dearth of juvenile crabs, scientists and watermen said, is especially troubling because of the species’ short and unpredictable life cycle. Blue crabs live only about three to four years. Females release their offspring near the mouth of the Chesapeake, where it meets the Atlantic Ocean.

After hatching, larvae – barely the size of a pinhead – drift in the ocean before returning on tides and currents, settling in underwater grass beds in the bay. If they don’t return to the bay, they’re essentially lost at sea.

According to the assessment, the invasive blue catfish, which preys on blue crabs, was responsible for reducing the juvenile crab population by an estimated 8 percent in 2023.

The number of female crabs has also dropped pretty consistently over the last decade, Miller said. He believes one reason is the females have had to compete with blue catfish for clams – and they really need the food. “They carry the energetic cost of bearing the next generation,” he said.

Crab-eating consumers, Miller said, may see a slight increase this year in crab prices at markets and restaurants but they won’t be exorbitant.

Watermen pointed to another possible factor: last year’s cold weather.

“We had a hard winter and we had a number of crabs die because of the cold,” said Robert T. Brown, a third-generation waterman in the St. Clements Island area of Maryland who has served as president of the Maryland Watermen’s Association for 13 years. “That happens. They don’t bury down far enough.”

Because blue crab populations swing dramatically, state fish and wildlife officials tightly regulate how many crabs can be harvested.

Brown said many watermen are frustrated by what they see as overregulation and are worried about the high costs of entering the industry, making it difficult to attract a younger generation.

“People who used to crab aren’t crabbing anymore because they’re in the graveyard,” Brown said. When he began in the mid-1960s, the average age of a waterman was in the early 30s. Now, he said, it’s in the upper 60s.

“You better have $150,000 in your pocket to get started in this business and not expect to get your money back for two or three years,” Brown said. “There’s no vacation with pay, no 401(k) plans and you start at 3:30 or 4 o’clock in the morning.”

This year’s season, which runs roughly from April through November, “hasn’t been great,” Brown said.

But he hopes for better.

“If you look in a crystal ball and try to predict it’s going to be a great year, it ends up being poor,” he said. But when “they’re saying it’s going to be one of the worst seasons we ever had, then it seems like we have crabs fall out of the sky.”

Dana Hedgpeth is a Native American journalist who has been at The Post for 25 years. She is an enrolled member of the Haliwa-Saponi Tribe of North Carolina. At The Post, she has covered topics including Native Americans and their history, Pentagon spending, the U.S. defense industry, and the local rail and bus systems, governments and courts.