Blue crabs in the Chesapeake Bay have dropped to a “distressing low” number, experts say, marking several years of repeated declines and raising concern about their long-term health.

The estimated number of crabs was 238 million, the second-lowest point since an annual blue crab dredge survey to measure their population started in the 1990s and coming shortly after 2022’s record low of 226 million crabs, according to experts. The survey found that the decline hit all of crustaceans, regardless of maturity or gender.

“It’s disturbing because we’ve seen in all sectors – adult males, adult females and juvenile crabs – drops in their numbers,” said Allison Colden, Maryland executive director for the Chesapeake Bay Foundation. The biggest concern, she and other experts said, is the drop in juvenile crabs.

“There’s a disconnect,” she said, “in the productivity of the blue crab population and the number of females in the water.”

The causes of their decline are a bit of a mystery to scientists. The blue crab population can vary widely each year, depending on several factors, including changes to their habitat – especially a loss of underwater grasses that are critical for young crabs, an increase in predators such as blue catfish and red drum fish, pollution runoff into the bay and dramatic shifts in wind, current and storm patterns that can especially affect juvenile crabs.

“If it gets too cold too quickly that causes them to die, and we’ve seen a very high rate of crabs dying over the winter,” Colden said.

The survey, conducted from December to March by the Maryland Department of Natural Resources and the Virginia Institute of Marine Science, gives a snapshot-in-time estimate of the number of blue crabs living in the bay.

Experts use a boat to drag a six-foot-wide dredge with a nylon mesh liner slowly along the bottom of the bay, taking samples from 1,500 sites for the analysis. The experts measure the collected crabs and calculate the average number of crabs in an area.

Experts examine the number of female crabs that could spawn in the coming year, which is an indicator of whether there will be a healthy crop of new crabs coming, and analyze the number of young crabs. The data helps experts manage crabs and regulate the number that can be caught and harvested each year.

Female crabs spawn their eggs at the mouth of the Chesapeake Bay, where it meets the Atlantic Ocean. When they hatch, the larvae – barely the size of a pinhead – develop in the ocean and return to the bay on tides, winds and currents, where they settle in underwater grass beds. They then disperse throughout the bay, mature in the rivers and mate. But if the tiny larvae don’t make it back to the bay, they’re lost in the ocean and die.

Changes in water temperatures and storm patterns are also affecting the juvenile crab population.

“If we have changes in weather and more storms – more frequent and more intense – that pushes crabs into the ocean and not into the bay, and we can lose a lot of those juveniles,” said Mandy Bromilow, manager of the blue crab program in fishing and boating services for the Maryland Department of Natural Resources.

She said over the past five years of the survey, there has been a decrease in the number of females and juveniles. This year, there were 108 million adult females – which is below the target population of 196 million. If it consistently remains low, she said, “you could have so few females that they’re going to have trouble sustainably reproducing the population.”

Rom Lipcius, a professor of marine science at the William & Mary Virginia Institute of Marine Science in Gloucester Point, Virginia, said that while the number of females has recovered after being over-harvested in the late 1990s and early 2000s, the number of juveniles remains low.

Another problem for juvenile crabs is one of their biggest predators, the invasive blue catfish, which is known to eat “whatever they can get their hands on,” Bromilow said.

Longtime waterman Chuckie White, who has been in the commercial fishing business for 46 years in Rock Hall on Maryland’s Eastern Shore, said he has noticed juvenile crabs “aren’t getting ample time to make it to legal size because of all the predators.”

His friend Donald Pierce, who has been in the business since 1971, said he has seen good signs in this year’s crab season, which runs roughly from March to November. Pierce said this spring, he put down 200 pots – used for catching crabs – around the Cape Charles area of the bay on Virginia’s Eastern Shore and caught the state’s daily limit – 22 bushels – of female crabs.

Keisha Sedlacek, federal director at the Chesapeake Bay Foundation, said in a statement that her group is also concerned that the “blue crab numbers are crashing just as the Trump administration dismantles programs restoring water quality and underwater habitat like grasses vital for crabs.”

Scientists in Maryland and Virginia are conducting a larger-scale assessment of the blue crab population, which will be completed in 2026. The last assessment was in 2011, and watermen and environmental experts said they’re eager to see the impact of changes in the climate and habitat, and of the increase in blue catfish population.

Lipcius said keeping the blue crab population healthy is critical for the bay’s ecosystem. Crabs eat worms, clams and smaller crabs, and they’re prey for sea turtles, great blue herons and fish.

“They’re a major node in the network and food web of the Chesapeake Bay,” he said, and they generate between $50 million and $80 million in the commercial harvesting business in Maryland and Virginia.

Watermen said they’re concerned but not alarmed.

“You have to give it time to work itself out. We’ve seen changes from time to time in every season,” said Robert T. Brown, a third-generation waterman in the St. Clements Island area of Maryland who has been president of the Maryland Watermen’s Association for more than a decade. “Sometimes these surveys come out and they say it’s going to be bad and it instead turns out to be a pretty good crabbing season.”

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