Trawls: Ocean Bulldozers
Trawls are large, cone-shaped nets that are towed along the ocean bottom or through the water, sweeping up just about everything in their paths.
Through their actions, they clear-cut the sea floor, which destroys ecosystems that may have taken centuries to form -- corals and rocky reefs, seagrass beds, etc. -- and eliminate hiding places that many marine species depend on for protection from predators. It is estimated that trawlers annually scrape close to six million square miles of ocean floor.
Shrimp trawls are the greatest culprit for catching unintentional catch, or bycatch, in their nets. Bycatch ratios around the world range from 3:1 to 15:1 of discarded dead or dying fish and other marine creatures (kilogram) to landed shrimp (kilogram). In all, shrimp fishing accounts for more than 27 percent of the world's unwanted catch.
Every year in the United States, the shrimp trawl industry discards millions of fish, sharks and endangered and threatened sea turtles. In the United States, estimates suggest that for every pound of shrimp landed, 4.5 pounds of bycatch are discarded in the south Atlantic and 5.25 pounds are discarded in the Gulf of Mexico. In 1997, shrimp trawl nets in the United States were required to place bycatch reduction devices (BRDs) on their trawl nets.
Since BRDs are expected to reduce bycatch by 30 percent, the ratios could be lowered to 2.8:1 in the South Atlantic and 3.5:1 in the Gulf of Mexico. Shrimp trawls are also required to use turtle excluder devices (TEDs) to reduce their catch of sea turtles.
If used properly, TEDs are up to 97 percent effective. Each year as the shrimp fishery season opens off the coast of Texas, hundreds of sea turtles, potentially injured and killed by shrimp trawl nets, wash up on south Texas beaches, suggesting sea turtles need our continued protection.