The sea turtle population has suffered tremendously as a result of bycatch losses, with six of the seven marine turtle species currently under threat.
Projeto Tamar Brazil
THE GIST:
- Millions of endangered sea turtles have been captured or killed by fisheries.
- At least four ocean regions require urgent sea turtle conservation.
- Consumers need to be aware that some seafood choices are more sea turtle-friendly than others.
Millions of endangered sea turtles have been accidentally captured or killed over the past two decades by longline, gillnet and trawl fisheries worldwide, according to a new report.
The report, published in the journal Conservation Letters, is the first global assessment of sea turtle bycatch for these three major types of fishing. Bycatch occurs when fishing equipment, such as giant nets or longlines with thousands of baited hooks, snag animals other than what they are intended to catch.
Turtles, which are air-breathing reptiles, often perish by drowning or by swallowing sharp hooks that can become lodged in the soft tissue of the turtles' throats and stomachs.
"For sea turtles, fisheries bycatch is the most serious, acute threat to the persistence of their populations," lead author Bryan Wallace told Discovery News, adding that shrimp trawling is one of the most damaging practices.
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"Anywhere from 5 to 20 pounds of bycatch -- turtles, fish, mammals, invertebrates, coral -- is removed from the ocean to catch enough for just a pound of shrimp," Wallace, a science adviser for Conservation International, said. "In the process, the destruction to ocean habitats left in the wake of a trawl net is very much like clear-cutting and bulldozing a tropical forest. That habitat is changed dramatically, and its recovery, if possible, will take a very long time."
Wallace and his team compiled a comprehensive database of reported information on bycatch rates for the three major types of fisheries worldwide from 1990 to 2008. The total reported global marine turtle bycatch was around 85,000. Since the data only covered less than 1 percent of total fleets, and didn't even include bycatch information from small-scale fisheries, the researchers estimate actual turtle bycatch at 8.5 million or more for the analyzed period of time.
The highest bycatch rates reported were from Baja, Calif., Mexico (longlines), Uruguay (trawls) and from the North Adriatic region of the Mediterranean (gillnets). Overall, however, four regions emerged as being the most urgent conservation priorities: the Mediterranean, the Eastern Pacific, the Southwest Atlantic and the Northwest Atlantic.
In the Mediterranean, for example, "21 countries fish an area that is less than 2 percent the total surface area of the Pacific Ocean and less than 30 percent of the total land area of the United States," Wallace said. "The European Environmental Agency estimated that 65 percent of all fish stocks in the Mediterranean are overfished."
The sea turtle population has suffered tremendously as a result of bycatch losses, with six of the seven marine turtle species currently categorized as "Vulnerable," "Endangered" or "Critically Endangered" globally by the IUCN Red List.
To combat the problem, Wallace and his team recommend regional governance, such as establishing marine protected areas. They also propose sustainable fisheries reform, including seasonal and time-area closures to fisheries, as well as selective gear modification, such as the use of circle hooks and Turtle Excluder Devices. Responsible seafood consumption by consumers is also key.
For the latter, Wallace recommends poll or troll caught fish, like tuna, mahi-mahi and wahoo that have not been longline caught. "In general," he said, "mahi-mahi is a better choice than tuna or swordfish, because mahi-mahi grow extremely quickly, reaching adulthood in as little as one year."
Additional sea turtle-friendly choices include lobster from northeastern or California waters; Australian rock lobster; king, stone and Dungeness crabs; calamari; Pacific Northwest salmon; farm-raised tilapia; and most farm-raised shellfish. Additional recommendations are available through services like "FishPhone," where users text in the name of a fish and get information on it in seconds.
A separate study, conducted by Duke University scientists, found that more than 250,000 loggerhead and 60,000 leatherback turtles are inadvertently snared each year by commercial longline fishing, with bycatch being particularly common in the Pacific Ocean. In fact, Duke's Larry Crowder, who worked on the study, said more turtles "are killed than nest in the Pacific."
Both he and Wallace hope the proposed conservation measures are enacted soon.
Wallace concluded: "A holistic, ecosystem-based approach that incorporates economic interests of the fishing industry has the best chance of success."
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