BALTIMORE — Big male crabs fetch the highest prices, but when it comes to ensuring the Chesapeake Bay will continue to produce those No. 1 males, researchers are increasingly paying attention to how many females are harvested.
A new assessment released Tuesday recommends how many female crabs should be in the bay to maintain a sustainable population. Biologists have previously said about 200 million adult crabs were needed to ensure a healthy population. The latest assessment released by the National Oceanic and Atmospheric Administration recommends fisheries managers work toward reaching a target population of 215 million adult female crabs and a total population of 415 million adult crabs. And when it comes to how many should be taken each year, the current recommendation is 46 percent of the population while the new assessment calls for a 34 percent target for female crabs.
Regulators are trying to refine how to manage a crab population that has seesawed in recent years, approaching nearly a billion in the early 1990s, but dropping to about quarter of that a decade later, and as few as 120 million adults, with overfishing blamed. Restrictions imposed beginning in 2008 included shortening the season and ending a winter dredge season in Virginia to protect hibernating pregnant females. Following those moves, the population rebounded to more than 650 million in 2010 before cold this past winter killed nearly a third of adult crabs. The latest winter dredge survey estimated the population at 461 million with 254 million adults and 207 million juvenile crabs.
The latest assessment found that under the new modeling approach the bay’s crabs stocks were not overfished in 2009, but had been from 1998 to 2004. Steps taken in 2008 to cut the female crab harvest by 34 percent likely led to an increase in adult females, boosting the population overall, the report said.
Peyton Robertson, director of the NOAA Chesapeake Bay Office and chairman of the Chesapeake Bay Program’s Sustainable Fisheries Goal Implementation Team, said that after a long period of decline the blue crab population is beginning to rebound.
“This new assessment will serve as a blueprint for the next stage of the rebuilding effort, moving us closer to a healthy, sustainable population,” Mr. Robertson said.
Despite this winter’s drop, fisheries officials said the population was still above restoration target levels and that has led to calls for easing the restrictions.
In Maryland, watermen will be able to catch more female crabs this fall, state officials announced in May, saying fisheries managers determined the increase won’t negatively affect the population. In Virginia, the winter dredge season has been closed for three years and regulators are considering whether to close it for a fourth season.
Mr. Robertson said the number of female crabs being harvested has been dropping.
“That suggests the measures in place are already achieving some benefit. Is that enough? We don’t know, but the trend suggests it’s going the right way,” Mr. Robertson said.
Fisheries managers will be using measures such as the winter dredge survey to see if the drop is enough to meet the new recommendations, he said.
Maryland and Virginia fisheries officials issued a statement after the release of the assessment, saying it showed fishery managers have only come close to achieving the recommended level of female abundance three times over the past 22 years, in 2010, 1993 and 1991.
Jack Travelstead, Virginia’s fisheries chief, described the recommendations as a sea-change in how the fishery will be managed, adding “it doesn’t appear Virginia will be in a position to relax harvest restrictions at this point.”
The Virginia Marine Resources Commission is scheduled to discuss the new stock assessment and vote on whether to close the winter crab dredge fishery for the fourth year in a row, as well as other crab conservation measures, on Aug. 23.
Tom O’Connell, director of the Maryland Department of Natural Resources Fisheries Service, said the new assessment is not expected to result in significant changes in managing the 2012 harvest.