Other Environmental Themes

The Tragedy of Bycatch

About a quarter of all the creatures caught in fishing gear throughout the world are the fishing industry's equivalent of "collateral damage." They're tossed out and left to die because the fishermen had different quarry in mind. These "non-targeted" species—fish, turtles, marine mammals, or seabirds—are discarded as refuse, or "bycatch," because they're too small, have little commercial value, or take up too much space on fishing boats. The shrimp industry, where bycatch often comprises 80 to 90 percent of the total haul, is one of the worst offenders. The non selectivity of commercial fishing is not just inefficient: Millions of tons of animals are needlessly killed each year.

Fortunately, technology can help reduce the carnage. In the Gulf of Maine acoustic alarms, or "pingers," are required on gillnets (wide-mesh nets that spare small fish but snare larger ones) to prevent the entrapment of whales, dolphins, and porpoises that are deterred by the unpleasant sound. Since 1992, shrimp fishermen in the Gulf of Maine have used another device, the Nordmore grate, to protect stocks of cod, haddock, and flounder. The grate consists of vertical bars—spaced far enough apart to let shrimp pass into the trawl net, while directing larger fish to an escape hatch above.

As mandated by federal law, the nets of U.S. shrimp trawlers in the Gulf of Mexico and south Atlantic are equipped with trap doors called Turtle Excluder Devices (TEDs). These inexpensive devices are credited with saving the world's smallest and most endangered sea turtle, the Kemp's ridley, from extinction. The number of Kemp's ridley nests found on the Padre Island National Seashore in Texas more than tripled between 1991 (one year after TED use became compulsory) and 1998.

There's one problem that neither TEDs, nor comparable technologies, can address, notes Ocean Conservancy biologist Marydele Donnelly. With multiple boats combing through crowded waters, a given turtle might be captured and released several times a day. This causes physiological stress in the form of "repeated and forced submergence," that may prove fatal. The only solution to that problem pertains, of course, to the over fishing problem as a whole: reduced fishing in particularly sensitive areas during particularly sensitive times.