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New challenge for Chesapeake Bay watermen: A shortage of crab sperm

Low blue crab counts have led to new restrictions on harvesting male and female crustaceans that go into effect July 1 in Maryland and Virginia

A blue crab comes up with oysters in a Chesapeake Bay cage in 2019. (Katherine Frey/The Washington Post)
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The Chesapeake Bay’s watermen have endured one crisis after another over the decades: persistent pollution, falling seafood populations, oyster-decimating diseases, shuttered processing plants, scarce pickers and rising prices for everything from gasoline to equipment. Now add a new crisis to the list: a shortage of crab sperm.

On Friday, new limits on how many blue crabs can be harvested from the bay will go into effect after an annual count revealed far fewer of the crustaceans than expected.

Blue crab population in Chesapeake Bay hits record low

The annual Baywide Blue Crab Winter Dredge Survey noted a serious decline in male crabs, leading to a new restriction on harvesting them. Scientists hypothesize that the falling number of male crabs has created a sperm shortage for spawning females, which could be one of the things contributing to the decreasing crab population.

Not good.

Under the new rules, daily commercial harvests will be cut by 15 to 25 percent, hurting watermen who depend on crabs for their livelihoods and threatening the supply available for summer crab feasts and locally sourced crab cakes on restaurant menus. Already, the retail price of blue crab is about $399 for a bushel of small crabs and $499 for large ones. The season will also end two weeks early, on Nov. 30.

“It’s not the watermen that are doing it,” said Bubby Powley, 72, a fourth-generation waterman who has been fishing off Hoopers Island in Dorchester County for decades. “We’re not getting rich by no means. The price of everything is going up, and our limits are going down. That’s where we are at. It’s not good for us.”

Most concerning, scientists say, are the long-term implications of the dwindling crab population in the United States’ biggest estuary. For 32 years, researchers have dredged 1,500 sites around the Chesapeake Bay annually to get an estimate of the number of crabs that overwinter there and a tally of how many were plucked during the previous harvest season. Since 2019, the total crab population in the bay has decreased by 60 percent.

In mid-May, the two state agencies that run the survey — the Maryland Department of Natural Resources and the Virginia Institute of Marine Science — made an announcement with more dire news. Only 227 million crabs had been counted, the lowest number on record since the survey began in 1990.

The survey revealed a plunge in the number of female crabs, from 158 million in 2021 to 97 million this year. It also found a three-year continuation of a below-average number of juvenile crabs, estimated at 101 million.

“There were two big red flags,” said Allison Colden, Maryland senior fisheries scientist for the Chesapeake Bay Foundation. “The lowest abundance on record since the survey began and also that we have lower numbers now than when Maryland and Virginia requested and were granted a federal fisheries disaster declaration in 2008. It’s hard to believe that the population was higher then than it is now.”

Then there was the decline in male crabs. With the count at only about 28 million, watermen will be limited to 15 bushels of males a day in August and September. In normal years, no more than 34 percent of the estimated male crab population is allowed to be harvested — a threshold so tough to surpass that only the harvest of females is usually monitored, ensuring that they continue to spawn.

Under the new restrictions, the harvest of females will continue to be limited — between nine and 17 bushels in July and August and 17 and 32 bushels in September and October.

Each female is capable of producing 3 million eggs in a brood, with up to three broods in a year, typically in mid- to late summer. They mate only once, releasing chemicals — akin to pheromones — into the water to attract a male. As the female sheds her shell, matures and hardens a new shell, the male protects her. In the process, she banks a cache of sperm that will last a lifetime.


But scientists point to two studies that indicate a shortage of sperm in the crab population, possibly leading to lower numbers of juvenile crabs.

“The male numbers being very low — and consistently low — that’s where some of our research comes in,” said Matt Ogburn, who works at the Smithsonian Environmental Research Center in Anne Arundel County. “If there are relatively few males proportional to the number of females that are maturing and mating, those males mate more frequently, as frequently as every few days.”

The problem with that, Ogburn explained, is that male crabs need about a week to rebuild their sperm stores. If they mate sooner than that, they’re not providing females with as much sperm as they normally would. A supply that should last years might last only one season.

“It’s estimated that females not getting enough sperm might be leading to a 5 to 10 percent reduction in the total number of fertilized eggs,” Ogburn said. “For the females that survive to a second summer, the amount of larvae they can produce is reduced.”

There’s a lot of other things that could be happening, too, researchers said, including:

  • Poor water quality with low-oxygen dead zones.
  • Loss of underwater grass beds that are critical nursing habitats for juveniles.
  • Predation by invasive species like blue catfish.
  • Pollution.

The new restrictions are stressing an industry of watermen already beleaguered by strict visa requirements that have limited seasonal migrant workers at the region’s crab houses and soaring prices on many supplies, including gasoline and paint.

“Unfortunately, everyone’s costs have risen significantly,” said Jack Brooks, owner of J.M. Clayton Seafood in Cambridge, Md. “We are working quite a bit thinner than we would like to. But I guess the restrictions are a necessary evil.”

When Powley was 32, he said, it cost about $8 to $9 to build a crab pot. Now, it’s $60 per pot.

“We just can’t stand it,” he said.

He’s not alone in those fears, though a good oyster season has helped offset them.

“We are very concerned about the male crabs, we are,” said Robert T. Brown, president of the Maryland Watermen’s Association. “This is our livelihood. If it goes bad, it goes bad on us. We are willing to make some concessions and try to keep the stocks up and everything.”

Brown sighed.

“We hope that next year will be better.”