While its difficult to separate the impact of longline fisheries from other threats turtles face, researchers say that the loss to longlines is significant because the turtles caught are often adolescents, which die before they have a chance to reproduce. Only about one in 5,000 turtles ever survive to adulthood. In the past, those lucky enough to last a few years in the ocean could expect a long life and would replenish the population. With the advent of longline fishing, the number of survivors has dwindled. A lot of turtles that beat the odds and would otherwise have lived long lives are now being caught on longlines, Lohmann said.
Lohmann, Wang and their team tested loggerhead turtles response to light sticks in a large, water-filled tank. Turtles were placed into a soft cloth harness and tethered to an electronic tracking device that monitored their movements. Safely encased in the soft fabric and released in the tank, the turtles swam as if in the open ocean, apparently unaware that they arent going anywhere, Wang said.
When glowing light sticks were introduced to the tank, the turtles swam toward them, as if curious about the lights, Lohmann said. The color or type of the light stick did not seem to matter. The turtles paddled toward green, blue and yellow light sticks, as well as toward both plastic chemical lightsticks and newer models based on reusable LEDs.
Both captive-raised and wild-caught juvenile turtles were attracted to glowing light sticks, whether in total darkness or underneath a night sky, Wang said. When the lights werent activated, they were unappealing. The experiments were conducted at the National Marine Fisheries Services Galveston Labora
Contact: Becky Oskin
University of North Carolina at Chapel Hill