Yes, rockfish eat crabs, but don't worry about it

ON THE BAY

February 06, 1993|By TOM HORTON

Last fall, fishing along the marsh edges in Tangier Sound, we got into a nice school of Crisfielders and hooked a couple. They were sporty devils and made several elegant leaps before we pulled them aboard, sleek as otters and pretty as trout.

In the old days we would have kept fishing and loaded the coolers with such fine specimens. Skinned, and soaked through three changes of water, then baked with plenty of onions to draw the gaminess, a Crisfielder makes passable eating.

But what we once considered so plentiful as to constitute almost a nuisance, we now recognize as a limited resource and a valuable part of the larger Chesapeake ecosystem.

So we were proud to keep just the two. It is heartening to see how conservation is paying off, as there are more Crisfielders around these days then anyone has seen in years.

But imagine our chagrin, cleaning them back at the dock, to find their bellies puffed like swelling toads, just busting with little blue crabs. In light of last year's disastrous crab harvest in these parts, it is pretty clear what we have done.

In our noble resolve to conserve Crisfielders, we have created a monster that, if unchecked, will forage ravenously up every river and marsh gut, capsizing the very ecosystem we were trying to balance.

*

The above is clearly fantasy; whoever would believe a Crisfielder makes passable eating? But a similar and equally implausible scenario is unfortunately becoming the stuff of legend throughout the bay.

Details vary, but the basic story is being retold from Norfolk to Baltimore, wherever watermen gather: Last year a crabber caught a striped bass, or rockfish, and noticed that its belly felt distended and lumpy, as if full of gravel. Cutting it open, he found it contained two dozen tiny hard crabs. (The number reaches 45 crabs in some versions of the tale.)

And the conclusion is always the same: The big comeback in the striped bass, the bay's premiere sport and commercial species of fish, is the reason crab harvests plummeted last summer to the lowest levels in years. The solution follows all too easily: It is time to loosen up conservation measures designed to prevent the overfishing that decimated bass populations in the 1970s and early 1980s.

MA These half-baked assumptions have produced a clarion call for

quick and forceful intervention on behalf of the poor crab. Some newspapers and legislators have taken up the cause, and fisheries managers in both Maryland and Virginia are being bombarded with letters from commercial seafood interests, charter fishermen and others.

Adding even more fuel to the fire, Maryland's top fisheries manager, William P. Jensen, has indicated to watermen and to the press that there might be something to the rockfish-crab connection.

Before we discuss why this view is wrong, and a dangerous approach to managing the Chesapeake Bay, let's look at where the various parties are coming from.

The bay's seafood community faces tougher regulations to limit crabbing. Most experts think last year's dip in the harvest was mostly due to weather; but they also acknowledge that fishing pressure on the blue crab -- from recreational crabbers as well as watermen -- has shot up in recent years to a dangerous level.

The rising pressure is well-documented. But humans seem to look incredibly hard for causes of environmental decline other than our own actions. A mysterious chemical, or too many rockfish, is easier to deal with than accepting limits or modifications on our behavior.

On the rockfish side of the equation, Mr. Jensen's Department of Natural Resources is under fierce pressure from fishermen, particularly charter boaters, to ease the limits for next year. Maryland is also jockeying with other coastal states for an increased slice of the rockfish harvest, under an agreement through which these states and the federal government set quotas.

It is possible that Mr. Jensen can make a responsible argument for in creasing rockfish quotas for the bay, based on some studies now under review by the other states; but it is irresponsible for him to perpetuate the rockfish-crab myth to do it. Here's why:

* Though rockfish do eat crabs -- occasionally, a lot of crabs -- they don't eat them very often. Several studies, some of them recent, show that crabs are a tiny fraction of the diet of a rockfish. The same appears true of weakfish and bluefish, along with rockfish the top predators among bay fish.

* One of the major predators of crabs, apart from humans, is the crab itself. Studies suggest that such cannibalism accounts for 25 to 30 percent of a crab's diet.

* There is absolutely no statistical correlation between years of .. abundant rockfish, as measured by commercial landings, and years of scarce crab harvests, according to a recent analysis by Maryland's DNR.

* Populations of anchovies and menhaden, the species that clearly are the preferred food of rockfish, show no unhealthy downward trends, despite the increase in rockfish in recent years.

This last fact is intriguing; more of the predator doesn't automatically mean less of the prey. Translation: Even if rockfish did feast on crabs, the crab population might not decline.

There simply are too many other variables in the environment. For example, reproduction of a species isn't directly related to how many adults survive to mate. A few survivors can produce a huge crop of young; conversely, a huge number of survivors may produce a modest number of young. In addition, a bumper crop of offspring doesn't automatically translate into lots of adults.

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