Sea Turtle and Pelagic Fish Sensory Biology: Developing Techniques to Reduce Sea Turtle Bycatch in Longline Fisheries

submitted to the 25 Symposium on Sea Turtle Biology and Conservation. Night-time spectral sensitivity of adult female leatherback sea turtles Levenson, D.H., Eckert, S.A. Crognale, M.A., Duhamel, P., Kubis, S.A. and Harms, C.A. Flicker electroretinography (ERG) was used to measure the spectral sensitivity of adult female leatherback sea turtles in vivo on a nesting beach on the southern Caribbean island of Trinidad. Individual turtles were selected for examination after the completion of nesting. Four turtles were successfully weighed, sedated, evaluated, and subsequently released without incident. Gross electroretinograms were monitored with a corneal contact lens electrode. Sensitivity was evaluated from 440 nm to 610 nm using flickering (4−12 Hz) monochromatic stimuli. Although testing was attempted beyond this range of wavelengths and flicker rates, measurable responses could not be obtained. Maximum sensitivity for all subjects occurred at or slightly above 500 nm in concurrence with previously reported rod photopigment sensitivity data for this species (maximum sensitivity 502 nm). Results indicate that the rod visual pigments of the leatherback are very similar to those of other sea turtles and are clearly not shifted in sensitivity below 500 nm as seen in many other marine animals active in deep sea environments. Interestingly, the ERG responses of leatherbacks were quite different from those of green and loggerhead turtles when similarly tested. This disparity suggests that further research may be merited into potential underlying differences in retinal organization among these species.