Rise and fall of blue crabs still mystery

ON THE OUTDOORS

March 03, 1996|By Peter Baker | Peter Baker,SUN STAFF

The start of good crabbing in Maryland waters of the Chesapeake Bay and its tidal tributaries still is three or more months away, but the regulations that will define how and when recreational crabbers may crab are being determined now in the state legislature.

Recent studies estimate there may be as many as 500,000 crabbers who are defined as recreational -- ranging from those who fish more than 300 feet of trotline or more than 10 traps or rings to those who once in a while tie baits to strings and spend an afternoon netting dinner.

In all, those crabbers might make as many as 2.5 million trips per year to crab, and estimates of their annual catch range from 11 million pounds to 40 million pounds. The latter figure would rival the annual commercial catch in the state.

The figures for recreational catch are inexact when compared to the records for commercial harvests, because fisheries managers have been unable to judge accurately fishing effort, or how many people crab how often and catch how many.

One proposal before the legislature this year is the implementation of a $5 license for those recreational crabbers who fish more than 300 feet of trotline or more than 10 traps or rings. Recreational crabbers who use less gear would not be licensed.

The question is whether licensing any recreational crabber is necessary, and if so, why?

Legislators on the Chesapeake Bay Commission say the license fee would help define the number of crabbers and raise $500,000 per year for crab research, which should help find the reasons for the fluctuations of blue crab populations in the tidewater.

Last week, representatives of the National Oceanic and Atmospheric Administration's Chesapeake Bay Office briefed the House Environmental Matters Committee on the status of crabs bay-wide. They said that despite 50 years of statistics and study, no one is certain why populations rise and fall.

"Every crabber knows that the biggest part of crabbing is how the catch changes," said Dr. Eugene Cronin, who has researched crabs since 1940. "Everything we know about crabs shows change, variations . . . that is why it is so hard to get a firm handle on what is happening and why it happens."

What is known is that crabs mate in the middle bay, and the females migrate south carrying the sperm, hibernate for the winter and spawn after the weather warms, primarily in Virginia waters at the mouth of the bay.

Once the female crabs have spawned, water currents help carry the young toward sheltered waters, where they hide, feed and pass through the stages of becoming hard crabs.

"The sweep of the tide is the biggest factor in whether there are small or large numbers of crabs," Cronin said. "But we are not certain that is the only primary factor."

Last year, Maryland's Department of Natural Resources moved to curtail the catch of female crabs, hoping to allow greater numbers of fertilized female crabs to complete their southerly migration. Virginia also has limited its take of female crabs.

Cronin said that more female crabs left alive should mean more crabs in the future, but catching a yet-to-be-defined portion of females should be allowed.

Dr. Anne Lang, also of NOAA's Chesapeake Bay Office, said bay-wide studies show that the total abundance of crabs dropped 30 percent from 1990 to 1995, and the number of crabs older than 1 year dropped 40 percent over the same period.

But, she said, abundance remains higher than the long-term averages, as it has been for the past 15 years.

In modeling sustainable fisheries limits, Dr. Lang said, managers first must know when too much is being taken from a resource. Bay-wide, she said, there is no evidence of overfishing in relation to the long-term average, and it is possible that crab numbers could return to the high averages of the 1980s without further restricting recreational and commercial harvests.

"But one of the concerns is that the effort has been increasing continually," Dr. Lang said. "If that increase is allowed to continue to climb. . . we cannot guarantee the future."

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