Earthwatch scientists provide hope for endangered loggerhead sea turtles snagged by longline fisheries

Earthwatch Institute, Maynard, MA, 28 February 2006-Every year more than 20,000 endangered loggerhead sea turtles are accidentally caught on the hooks of longlines used for catching swordfish off the southern coast of Spain. Now Earthwatch-supported scientists reveal that the turtle mortality by longline fisheries in the Mediterranean Sea can be reduced by as much as 80 percent if fishermen bait their hooks with mackerel and fish at slightly deeper depths.

Scientists Ricardo Sagarminaga van Buiten (Spanish Cetacean Society) and Ana Cañadas (Alnitak and University Autónoma of Madrid) spent 30 days working with local fisherman onboard a longline fishing vessel, where they conducted 15 experiments using a normal long line with forty baited hooks. When the fisherman substituted their traditional squid bait for mackerel and fished the hooks slightly deeper, the results revealed a significant reduction in turtle bycatch numbers, while the target swordfish catch remained the same.

"We are very pleased with the result of this experiment," says Sagarminaga, president of the Spanish Cetacean Society and co-principal investigator of Earthwatch's Spanish Dolphins project. "Perhaps the most positive outcome is the interest we have received from local fishermen who are now willing to cooperate with us to find scientific solutions to the bycatch crisis."

The experiment was modeled after a similarly successful study in the North Atlantic by the U.S. National Marine Fisheries Service, and was conducted with their assistance. The study was part of a long-term research project to find solutions to the bycatch problem, initiated by the Alnitak Marine Environment Research and Education Centre, the Spanish Oceanographic Institute, and Dr. Scott Eckert. Eckert, assistant research scientist at Duke University and director of science at the Wider Caribbean Sea Turtle Conservation Network (WIDECAST), is also a veteran principal investigator of Earthwatch sea turtle projects, including the current Trinidad's Leatherback Sea Turtles project.

Teams of Earthwatch volunteers have supported Cañadas and Sagarminaga's research since 1999, working on board a 20-meter wooden vessel in the Alboran Sea to monitor dolphins and other marine inhabitants. Cañadas and Sagarminaga were chosen by the European Commission and Spanish agencies to create management and monitoring schemes for marine protected areas proposed on the basis of this Earthwatch-supported research.

Over the last two years, Sagarminaga, Canadas, and Eckert have deployed satellite-linked data recording transmitters to loggerhead sea turtles in the western Mediterranean. Data from this satellite telemetry study indicate that the turtles stay mainly in the top six meters of water when passing through longline fishing grounds. This finding led to idea that setting longlines deeper could avoid the accidental capture of sea turtles, but it was unknown if this change in fishing methods could still catch swordfish until Sagarminaga and Canadas conducted their experiment.

The team hopes that this information will help the longline fishery to mitigate the bycatch problem and highlight the importance of international coordination for the conservation of loggerhead turtles and other wide-ranging ocean species.

"We are delighted to be associated with this excellent piece of applied conservation work, in which the scientific studies have been conducted with the fishermen to show how turtles can be better protected, while not reducing the fishermen's catch." says Dr. Roger Mitchell, chief scientist at Earthwatch (Europe). "Earthwatch is always seeking new ways of managing the exploitation of natural resources to ensure that populations of both the species targeted, and those indirectly affected, are sustained over time."

Earthwatch Institute is a global volunteer organization that supports scientific field research by offering members of the public unique opportunities to work alongside leading field scientists and researchers. Earthwatch's mission is to engage people worldwide in scientific field research and education to promote the understanding and action necessary for a sustainable environment. The year 2006 marks Earthwatch's 35th anniversary.

Learn more about how to volunteer on Spanish Dolphins.

Find more information on Alnitak.

Find more information about the Wider Caribbean Sea Turtle Conservation Network.