Survey finds Bay crab population strong, with record number of females
Scientists credit conservative management, expect good harvest, but some voice caution over dearth of juveniles
Boosted in part by a record number of female blue crabs, the Bay’s crab population remained strong through the winter — something scientists say bodes well both for the crustaceans and those who catch and love to eat them.
Overall, the annual winter dredge survey conducted by Maryland and Virginia estimated that the Bay held 455 million crabs, a decrease from last year’s tally of 553 million. Most of the drop was attributed to a falloff in juvenile crab numbers, which are both more variable and harder to survey.
But survey results released Wednesday showed that the number of female crabs — which have been the focus of conservation efforts for nearly a decade — reached 254 million, a 31 percent increase over last year, and their highest level in the survey’s 28-year history.
As a result, fishery managers expect solid harvests this spring and into early summer, buoyed by the large number of adult crabs from last year. But they warn that the low number of juveniles “recruiting” into the overall population may require some harvest restrictions when the young crabs start reaching market size later this year.
“I’m pretty confident the stock is solid,” said Rom Lipcius, of the Virginia Institute of Marine Science, who helps oversee the annual survey. “But we need to be careful. We can’t just open up the fishery and stuff, especially with what appears to be lower recruitment.”
The survey, conducted in the winter when crabs are normally dormant on the bottom, is a closely watched indicator of the status of the Bay’s most valuable fishery. State fishery managers typically tweak catch levels, both up and down, based on the results compiled by VIMS and the Maryland Department of Natural Resources.
For instance, the states imposed catch restrictions to reduce the Baywide harvest 10 percent in 2014, when the survey revealed the number of females had sharply dropped. But managers have also eased restrictions when the crabs are found to be more plentiful, as they did last year.
While there have been ups and downs from year to year, survey data show that blue crab abundance has trended upward overall since 2008, when scientists warned the population was dangerously close to collapse. Maryland and Virginia acted together then to impose harvest limits on female crabs, allowing more to survive and reproduce.
Though the total number of crabs was down in this year’s survey, it was still the third highest since 2008.
Harvests have rebounded as well. An estimated 60 million crabs were caught Baywide last year, up from 50 million in 2015, and the record-low of 35 million a year earlier.
“I feel optimistic in the grand scheme of things,” said John M.R. Bull, commissioner of the Virginia Marine Resources Commission. “The trend line is that the stock has improved, and the harvest has improved at the same time.”
This year was the second time since 2008 when the number of female crabs exceeded the Bay target of 215 million recommended by scientists. It was only the third time in the history of the winter dredge survey that it had exceeded that mark.
"The good news is we’ve got a bunch of momma crabs out there," said Robert T. Brown, president of the Maryland Watermen's Association. "Hopefully, they hatch out good."
Watermen in some areas have been reporting catching a lot of female crabs, Brown said, to the point that some are shifting their gear to try to find more males.
One concern voiced by scientists and fishery managers was the relative dearth of young crabs in the survey. The 125 million baby crabs estimated this winter was the lowest since 2013, and the second lowest since 2007.
Scientists cautioned that the juvenile numbers have the highest level of uncertainty in the survey because the small crabs sometimes move into shallow water where they are hard to find.
Other factors can contribute to wide swings in juvenile numbers, Lipcius said. Juveniles spend the first several weeks of their lives drifting in the ocean after they are spawned, and weather conditions greatly affect the number that return to the Bay. Those that return can suffer heavy predation from fish, and even cannibalism when they are eaten by large numbers of adult crabs.
“One low year of small crabs is not by itself a danger sign,” said Tom Miller, a fisheries scientist and director of the University of Maryland Center for Environmental Science’s Chesapeake Biological Laboratory. But, Miller cautioned, a low number of juveniles would be a concern if it continues for another year.
Fishery managers in both states said they may consider action to protect those juveniles, perhaps by curbing catches later this fall and next spring when they reach market size. That would increase the chances that more of them would survive to reproduce and support future harvests.
“We need to be prepared for the challenges ahead of us as it relates to the juveniles,” said Mike Luisi, assistant director of fisheries and boating services with the Maryland DNR. “We want to make sure that we’re not overharvesting on that lower abundance.”
Matt Ogburn, a fisheries scientist who works with blue crabs at the Smithsonian Environmental Research Center in Edgewater, MD, said the fact that crab numbers have generally risen in recent years, along with harvests, offers “a good example of how fairly conservative management actions can actually lead to increases in the fishery.”
“As short-lived as they are, blue crab populations can decline very quickly if you’re not careful,” Ogburn said. “But they can also come back quickly if you are conservative about the management. And I think the last decade has proven that out.”
Nonetheless, those decisions can be difficult. A longtime crab manager with the Maryland DNR, Brenda Davis, was fired earlier this year after a group of Eastern Shore watermen complained about her unwillingness to ease crab harvest rules. The firing prompted outrage, and a legislative hearing in Annapolis.
“It’s almost more difficult, scientifically, to manage a rebounding fishery,” Miller said, “because it’s a question of how much is enough…if we change the regulations, how much is that going to impact the harvest?”
The winter dredge survey has been conducted annually since 1990 by scientists in Maryland and Virginia, who tally crabs dredged from the bottom at 1,500 sites across the Bay from December through March — when they are buried in mud and stationary. Historically, the survey has provided an accurate snapshot of crab abundance, and is the primary tool for assessing the health of the crab stock.
- Category: Fisheries
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