ECOVIEWS
DO TURTLE EXCLUDER DEVICES PROTECT SEA TURTLES ?
Not long ago, an estimated 55,000 sea turtles were killed annually by U.S. shrimp trawlers. However, barring an upswing in other sources of mortality, researchers from North Carolina State University and South Carolina's Department of Natural Resources offer an optimistic outlook for their recovery. L. B. Crowder, S. R. Hopkins-Murphy, and J. A. Royle published their statistical analysis of fourteen years of records in the scientific journal Copeia .
In 1980 the National Marine Fisheries Service established a network to determine the numbers of dead sea turtles washed ashore, especially due to shrimp trawling in the South. The number of nesting turtles on beaches are a secondary measure of whether sea turtles are declining or increasing in an area.
The investigators tallied results of patrols along South Carolina beaches to establish trends in the numbers of loggerhead sea turtle carcasses stranded from 1980 to 1993. Their focus was on whether the use of turtle excluder devices (TEDs) by shrimp trawlers reduced the number of turtles killed. TEDs are grid attachments within trawl nets that retain shrimp but allow most turtles to escape. Without TEDs, shrimpers kill turtles, albeit incidentally and unintentionally, by drowning them in their nets.
Federal laws passed in 1989 require U.S. shrimp trawlers to use TEDs, although court challenges were made. Also, critics claimed that no quantitative scientific evidence was available to support contentions that TEDs saved turtles.
During the first eight years of the study on loggerheads, no TEDs were in use. During the last four they were on all shrimp trawlers in South Carolina. Based on the decrease in numbers of dead loggerhead sea turtles over the years, TEDs had reduced mortality by approximately 44 percent.
Before the use of TEDs, when shrimp season opened in South Carolina and Texas, the number of beached turtles quadrupled. When shrimping stopped, stranded carcasses decreased in number. Nesting populations in South Carolina, where shrimp trawling is high, were declining, but have stabilized since TED use began. In the parts of Florida where shrimp fishing is absent, nesting was stable or on the increase.
A key point about the published study is that political rhetoric is removed from the environmental issue of whether traditional shrimp trawling has an impact on sea turtles. The problem became apparent in the 1980s when an environmentally sensitive Congress ordered an independent review of the conservation status of sea turtles. The committee of scientists was to determine if commercial fishing and shrimping caused mortality of sea turtles. They considered environmental impact only, not sociological or economic issues.
The 1990 book "Decline of the Sea Turtles: Causes and Prevention" declared shrimp trawling to be the most significant cause of death to sea turtles along U.S. coastlines. With the loss of eggs and hatchlings under control, the loss of older age classes was judged to be the primary problem in the decline of sea turtles. The suggested remedy was to require the use of TEDs.
Five species of sea turtles occur in U.S. coastal waters in the Atlantic and Gulf of Mexico. All are protected under the Endangered Species Act, which remains intact despite special interest attempts to demolish it. The U.S. shrimping industry operates from Cape Hatteras in North Carolina to the Texas-Mexico border in the Gulf, with the exception of central to southern Florida on the Atlantic side, where less shrimp trawling is done. Forceful conservation measures must continue if sea turtle populations are to persist.
Many shrimpers, especially in the Gulf states, consider TEDs an inconvenience that reduces the shrimp catch. Proponents argue that TEDs do not reduce the catch appreciably and that shrimpers are resistant to the idea because they do not want to be told how to run their business. Whatever the effects on the economics of catching shrimp, the published study demonstrates that TEDs do indeed reduce sea turtle mortality.
Unfortunately, the Young-Pombo bill being proposed in Congress would eliminate the requirement that TEDs be used. If Congress passes the bill, they will eliminate a lot of sea turtles, and a lot of environmental progress.
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