Many of those concerned about the oceans, from conservationists to fishers, have recommended strategies to promote sustainable fisheries. One proposed strategy is to ban the use of large bottom trawling gear that some analysts claim is destroying fisheries. Industry advocates argue, however, that these bans will economically devastate fishing communities without averting the damage that they are designed to prevent.

Bottom trawl nets are like enormous butterfly nets. The “footrope,” the bottom edge at the mouth of the net, is usually made of heavy-gauge chain rigged with weights and rollers or rockhoppers. Rollers are steel or rubber tires or balls that rotate on the footrope as it drags across the ocean floor. Rollers, which can be from four to eighteen inches in diameter, reduce the amount of mud that the net collects. Because bottom trawlers using rollers could...