Protection for crab breeding cycle must extend beyond state, Chesapeake Bay

OUTDOORS

June 20, 1993|By PETER BAKER

The crabs clung to the shaded side of an outboard piling near the surface of the placid creek at dusk, the jimmy cradling the female in its walking arms and vigorously finning the water with its swimming legs.

The jimmy's choice of cover was as yet poor, but with the female settled contentedly in the cradle, the jimmy would carry them both from the piling into a nearby grass line or perhaps to a recess in a bulkhead, stand guard as the female completed her final molt and then mate.

The same process will be completed millions of times by millions of Atlantic blue crabs through the late spring, summer and early fall in the Chesapeake Bay and suitable areas of its tidal tributaries.

In two years, the females hatched by this year's sooks will themselves dance through courtship, cradle, molt a final time, breed and make the long, final journey to the spawning waters at the mouth of the Chesapeake Bay.

In an effort to ensure that there will be sufficient numbers of blue crabs to complete the life cycle in coming years, Maryland has formulated the Crab Action Plan, a series of restrictions proposed for commercial and recreational crabbers in state waters.

The action plan has stirred debate among watermen and non-commercial crabbers alike. The trouble is, Maryland crabbers will say, that while the restrictions might stabilize the crab catch in this state, it does not -- and perhaps cannot -- address other factors that have a major impact on crab population.

The doublers hanging in the shade of a single piling 80 and more miles from the mouth of the Chesapeake Bay have made a hard journey from the spawning grounds.

As larvae they have drifted to the Continental Shelf, undergone seven or eight molts or shell sheddings to grow to perhaps a hundredth of an inch and become megalops, capable of erratic swimming skills and with strong walking legs.

The megalops, given the right water temperature and salinity, will move into the mouth of the Chesapeake, settle to the bottom, change again into a fully formed blue crab and still be the size of a ball point pen tip.

But water that is too cold or too fresh will delay the metamorphosis from megalops to blue crab and the life cycle may be thrown off schedule, seemingly creating a shortage of crabs.

Take this spring, for example. In March and early April, heavy snowfall and rain sent a slug of cold, fresh water into the Chesapeake Bay. The Susquehanna ran high and cold at the head of the bay. In mid-bay, so did the Potomac. And near the mouth of the Chesapeake, the James River did the same.

What impact will those large pulses of runoff from the bay's 64,000-square mile watershed have? The immediate impact on crabs should be slight, and already this year the crab catch is brisk, prices are down and numbers of juvenile crabs can be seen in their migration up the bay.

But what of next year?

Research by Duke University's Dr. John D. Costlow, recounted in William W. Warner's book, "Beautiful Swimmers", shows that the megalops will suspend for as long as three months its development to the tiny blue crab if conditions are not correct.

When the conditions are in proper balance again, the megalops will resume its development. But a two- or three-month lapse this spring may result in a shortfall in the spring of 1995 -- and perhaps a crab bonanza that fall.

And perhaps here is where the Crab Action Plan might do its best work. If the catch by commercial and noncommercial crabbers is stabilized, then pulses in the crab population might not be overfished.

In all this there is a major factor that must be considered and one that Gov. William Donald Schaefer says he will attempt to address.

The male crab hanging in the shade of the piling will mate and eventually make its way to deeper waters in the upper bay. The sook, with sperm of the male stored for later use, will migrate toward the mouth of the bay, bury in the muddy bottom and produce and fertilize some 2 million eggs next spring.

And the cycle should begin again.

However, in Virginia waters of the Chesapeake, crabbers are permitted to dredge the muddy bottom for crabs through the winter.

In a news release announcing the formation of the Crab Action Plan, Schaefer said, "If we have learned anything from the striped bass crisis in the 1980s, it was the importance of taking early and decisive action.

"Although the Chesapeake Bay's crab population appears healthy now, the fishing pressure has been increasing and we should not wait to see a significant decline before setting a strong management plan into effect."

But with rockfish, Maryland has jurisdiction over the most fertile spawning grounds on the East Coast, and the species has been recovering in its coastal range because the spawning grounds and the brood fish that migrate there have been protected.

Can a Crab Action Plan be effective in Maryland if the blue crab spawning grounds in Virginia are not protected in similar fashion?

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