A six-year survey of Chesapeake Bay blue crabs shows a population decline of more than 60 percent through last winter, and early returns this winter indicate a continued drop for the bay's most popular and valuable seafood.
Maryland and Virginia scientists who cooperated in developing the survey of crab abundance at 1,200 locations say it is the latest and most authoritative warning that the bay population could be in danger of depletion from overfishing.
Some watermen and officials in Maryland question the survey's reliability. But its findings have triggered debate over whether more restrictions on crabbing are needed, less than a year after both states moved to slow down or limit what had been a growing industry.
"We're all very concerned right now," said Romauld Lipcius, a crab researcher at the Virginia Institute of Marine Sciences in Gloucester, Va. "It doesn't appear that the population has quite collapsed, but it is at a very low phase."
Starting in winter 1988-89, scientists at the University of Maryland's Chesapeake Biological Laboratory, with help from the Virginia institute and the Maryland Department of Natural Resources, have made annual surveys of the number of blue crabs slumbering on the bay bottom. Free-swimming during other seasons, crabs tend to settle in the mud during the winter's cold, making it easier to count them.
With the same type of iron dredge used by Virginia watermen during their winter harvest of hibernating crabs, researchers sample the 1,200 sites, chosen at random, and the Chesapeake lab in Solomons compiles an index of crab abundance.
The index represents the number of crabs hauled in by the dredge for every thousand square meters of bottom sampled. The index also is used to estimate the total population.
Scientists hope that the survey, developed with $2.5 million in federal funds, can be used by natural-resources officials to monitor the condition of the Chesapeake's last healthy fishery.
"If we can track numbers, this gives managers the ability to tighten up before [crabs] are overfished," said M. Elizabeth Gillelan, director of the National Oceanic and Atmospheric Administration's Chesapeake Bay office in Annapolis, which financed the survey.
Though still being refined, the survey gives a reliable picture of the crab population and should be heeded, Ms. Gillelan said.
The survey's abundance index fell from 26.23 in winter 1988-89 to 9.97 last winter, a drop of 62 percent. The index translates into a population estimate of 1.75 billion crabs in winter 1988-89 and 664 million last winter -- also a drop of 62 percent.
According to the survey, the crab population hit an even lower point, 440 million, in winter 1991-92. From 1988 to 1993, the most recent year for which final catch figures are available, the combined commercial harvest for Maryland and Virginia averaged 87 million pounds, with a low of 54 million in 1992 and a high of 113 million the next year.
Harvests do not always reflect how many crabs there are, scientists say, because fishing effort may vary. But crabbing has expanded in the bay in recent years, and scientists estimate that from 50 to 92 percent of all harvestable crabs are caught every year.
The survey this winter began in December and continues through February. Preliminary results from sampling in the mid-bay indicate a significant decline in abundance compared with last year.
Lonnie Moore, a Tangier Island waterman who does the mid-bay dredging for the survey, said that on average he has found 40 to 50 percent fewer crabs than a year ago in each haul this winter, and the decline in adult female crabs seems even greater.
"If our preliminary samples from this year are consistent to the end of the sampling period, this will be one of the lowest indexes we've had," said Brian Rothschild, the Chesapeake laboratory researcher who coordinates the overall survey.
Alarmed by the six-year decline in population, some environmentalists are calling for further curbs on commercial crabbing, in addition to the recent limits on gear and hours and efforts to hold down the number of crabbers.
"I don't think there's any question that we're overfishing blue crabs," said William Goldsborough, fisheries scientist for the Chesapeake Bay Foundation. "We have to look seriously at reducing [fishing] effort."
In Virginia, the survey findings come at a time when watermen are suffering through one of their worst winter crab seasons in memory.
Jack Travelstead, fisheries manager for the Virginia Marine Resources Commission, said he has no immediate plans to impose new restrictions on crabbing. But he noted that two bills in the Virginia legislature call for study of more curbs.
In Maryland, fisheries officials and watermen say there is no cause for panic.
The survey is too new to be definitive, they say, and crab stocks fluctuate widely from year to year because of natural factors.
"You can't draw a conclusion that because the resource has declined, it's in any kind of trouble," said W. P. "Pete" Jensen, fisheries director for the state Department of Natural Resources. He said the survey techniques have been altered over the years, making year-to-year comparisons questionable. And he said he has seen no other evidence that the bay's crab population has entered a long-term decline.
"It's too early to make a decision that we're in trouble here," agreed Larry W. Simns, president of the Maryland Watermen's Association. He said fishing presure on crabs already is easing ,, up, because of new Maryland regulations limiting the number of crab pots and the hours for commercial crabbing.
But Virginia's Dr. Lipcius said the findings of the abundance survey dovetail with the results of other scientific surveys done for years in the lower bay.
POPULATION DECLINE
HARVEST PRESSURE ON CRABS IS HIGH....
Watermen in Maryland and Virginia depend on the blue crab as their main source of income because of the decline of oysters in the Chesapeake Bay. This means that a high percentage of the crab population is caught every year.
....BUT BAY'S CRAB STOCKS HAVE FALLEN
Annual winter survey of hibernating crabs shows that the overall population is at a relatively low ebb, meaning that a continued high catch rate could undermine the fishery by removing too much breeding stock.