Crabs: To worry or not to worry? The ultimate survivor? Amid concerns about overfishing, a recent study found an uptrend in the numbers of small crabs and annual harvests significantly below the danger point.

On the Bay

March 08, 1996|By Tom Horton | Tom Horton,SUN STAFF

IT IS REASONABLE to ask whether the modest new fishing restrictions announced this week by the state are enough to protect the bay's crabs.

But an opposite question might seem as reasonable:

Do we need to worry even modestly about the crab? Might it be the ultimate survivor, nearly invulnerable to overfishing?

The suggestion seems ironic, considering that even watermen increasingly are buying the conventional wisdom about crabs: that increased pressure in recent decades has pushed them close enough to the breaking point that limits are in order.

But consider recent findings of the most comprehensive attempt to date to assess the health of the bay's crabs: ......TC There is no evidence of any downtrend. The numbers of small crabs show a solid uptrend.

Not only is the crab not being fished beyond the point of biological health, but annual harvests are significantly below any danger point.

Put another way, the study estimates that current harvests leave on average about a third of the adult spawning stock of crabs alive to reproduce the next year.

Leaving a fifth would be quite enough, the study's investigators say, based on all that is known about the management of crustacean fisheries around the world. Even leaving a 10th, they feel, probably would be sufficient.

The crab "stock assessment" was made by the Chesapeake Bay office of the National Oceanic and Atmospheric Administration (NOAA), using the expertise of nine experienced fisheries scientists from several states, including the bay region.

Even the scientists doubted their results at first. The sentiments of one were typical: "I have done these assessments for more than a decade on nearly every commercial fish species along the East Coast, and this is the first time one has ever come out on the side" that there has been no overfishing.

Which does not prove they were right; but neither can you dismiss such a group as apologists for fishing or political interests.

I think the stock assessment is a valuable effort and perfectly credible within the limits of our knowledge of the bay's crabs.

But, as the stock assessment leaders themselves point out, it would be folly to use it to throw caution to the winds.

"Nothing we have said means we should roll back efforts to manage crabs," says Bess Gillelan, head of NOAA's Chesapeake Bay office.

What is all right for the health of the species is not automatically beneficial to those who catch them, she says.

An example -- and a part of the assessment that often brings skepticism -- is its apparent rejection of overwhelming anecdotal evidence that watermen today use many more crab pots to catch the same number of crabs they always did.

Most people, including scientists, have assumed that this means the number of crabs in the bay is shrinking, even as more gear and effort and technology prop up harvests.

But the NOAA team's evaluation said there is no evidence of a shrinking pie -- just a stable pie that is being sliced up ever smaller, among more and more crab pots.

The latter interpretation means crabs are OK. But in neither scenario are watermen OK; rather, they are straining harder every year just to keep up.

There are other reasons to keep the assessment in context.

The assessment is not new research, but rather an evaluation based heavily on earlier data of fluctuations in crab abundance.

Reliable data go back only a short time, from as little as five years to a couple of decades. What might the picture look like in the context of, say, a century?

To use an extreme example, consider that a huge storm in June 1972 dumped more sediment into the bay in a few days than it usually gets in half a century. Previously, you might have had many decades of data and not really known much about sediment and the bay.

Also, even the most scientific of stock assessments, biologists will tell you, rely on a measure of wisdom and judgment.

An example: In determining whether crabs are overfished, it is critical to know their normal life span -- the shorter it is, the less you have to worry. But no one living has studied crabs in a natural situation, where an absence of fishing pressure lets them live more than a couple of years.

The stock assessment, after much agonizing and chasing down stories of crabs up to an unlikely 8 years old, chose four years as the normal life span (even six years wouldn't have led to a conclusion of overfishing, they maintain).

And there are crab experts, including Romuald Lipcius of the Virginia Institute of Marine Science, who feel that the stock assessment overstates the health of the species.

Dr. Lipcius thinks a better historical look at crabs would show they were not as unusually abundant as the assessment assumes during the 1980s.

Thus, he argues, the drop in population that everyone agrees has occurred during the 1990s would not be, as the assessment says, still well within the bounds of normal but rather would be reaching a worrisome ebb.

From year to year, crabs boom and crabs go bust, and boom again. They have humbled the most cunning watermen, the smartest scientists -- even (blush) the sagest of bay writers -- and they will again.

Yet, the science does get better, and at an increasing pace these days; and watermen and regulators in Maryland and Virginia seem closer than ever to reaching a fair and conservative accommodation.

Pub Date: 3/08/96

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