Lest we lose sight, amid the clangor of contending crises, of heady progress in the march toward a better world, let us note right here that technology appears to be closing in on the problem of hairy crab pots.
The Virginia Institute of Marine Science at Gloucester Point has embarked on a project this spring, in fact, to gather the data and help ensure biota-free traps for the blue crab of Chesapeake Bay.
Liberating watermen from the hirsute burden of marine growth, crabbing sources say, could prove to be the greatest economic boost for commercial crabbers since the sacrificial zinc. Maybe even the greatest since 1928, when B.F. Lewis of Harryhoughgan, Va., invented the crab pot itself: a two-foot cube of galvanized wire mesh into whose labyrinthine bowels crabs are lured by a pound of mashed herring.
Where we could go from here boggles the mind.
The problem is as old as the trapped crab. In the sultry months of July and August, especially, the bait-weighted sunken cages on the sandbars of the bay sprout a stringy, slimy, greenish-black, moss-like substance referred to by watermen as "hair."
So fast and thickly does it grow that crabs soon shun the fouled traps with the repugnance of a gourmet toward a mildewed luncheonette.
"Crabs won't go in where they can't see through," says Mike Oesterling, a crab-minded fisheries specialist at VIMS, who says that crabbers in some areas of the bay must pull up, dry out and wire-brush their pots twice a season. "Fouled pots cost money in terms of reduced catches and hours spent cleaning them, plus the wear and tear on the pots themselves."
At $10 to $12 apiece, the pots, which rarely last more than two years, represent an annual expense of $3,000 to $4,000 for the bulk of the bay's 9,000-odd commercial crabbers.
Enter John Pettit of Roseland, N.J., who makes deck and hull paint for the yachting trade, but maintains a scholarly interest in crabs and crabbing. Twelve years ago, he says, he came upon a waterman on Tilghman Island, Md., drying out crab pots "so thickly covered with hair you wouldn't believe it," and asked about the growth.
The problem, he learned, was two-fold. One part was the biology of the "hair," actually the weed-like hydroid or polyp stage of a primitive animal--a hydrazoan--that spends the other half its life as a transparent, free-floating jellyfish about the size of a human fingernail. The second part of the problem lay in the necessarily fragile structure of the crab pot itself, which begins decaying as soon as it hits salt water.
Some years ago, crabbers discovered that wiring a small ingot of pure zinc to each pot retarded much of that decay, doubling the life of pots that previously had rarely lasted one season. The ingot, called a sacrificial zinc or anode in the trade, served as a lightning rod for much of the galvanic action eating into the crab pot's wire mesh.
Watermen found that they could further lengthen the life of their pots by making them with vinyl-coated mesh, which added about
.50 to $2 to the cost of a pot but made it easier to handle. Vinyl pots, however, foul even faster than metal ones, especially in the Chesapeake Bay's brackish tributaries.
Pettit thought that the answer might lie in painting the pots with the sort of antifouling paint used to retard marine growth on boat hulls. That, however, proved both prohibitively expensive and chemically unsuitable: The copper oxide in the paint greatly increased the destructive electrolysis. Even on the vinyl pots, the bare metal ends of the plastic-covered mesh were vulnerable.
So Pettit developed a new paint containing tributyl tin oxide, a chemical almost as toxic to the hydrazoa as copper oxide but cheaper and more compatible with the metal in the traps.
Pettit is president of U.S. Yacht Paints and presumably has other duties, but has made the crabbing-paint corner of his business "a personal project of mine . . . . I haven't even put a salesman on it. I just tell any waterman who hasn't used it I'll paint 10 of his pots free. He can make his own comparisons after that."
Other researchers have been more formal. A study by the Maryland Department of Natural Resources a few years ago found that the paint did reduce fouling significantly. The ongoing VIMS study is designed to find out how much, and to gauge its effect on pot longevity.
The paint, which retails for around $22 a gallon, adds about a dollar to the cost of a pot, but Oesterling says there are indications that it may stretch pot life in some areas of the bay as much as two years.
He says that VIMS purchased 180 crab pots at the start of the season, half of them vinyl and half galvanized metal, painted half of each batch and distributed an equal assortment to three crabbers, one who crabs Hampton Roads, one the York River and one the Potomac River. Oesterling and two researchers will compare fouling resistance and durability, not only between painted and unpainted pots, but between vinyl and metal as well.
Pettit, who donated the paint for the experiment, is content to wait for the results. He says that, although still relatively untried in Virginia, his paint now is sold by 26 dealers in nine states, and he estimates that two-thirds of the crabbers who have tried it now paint their pots regularly, and their buoy lines as well.
The paint, he reports, even keeps slime off the lines.