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Physiology Experiments Aimed at Reducing Pelagic Longline Interactions with Marine Turtles Yonat Swimmer, University of Hawaii Richard Brill, National.

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Presentation on theme: "Physiology Experiments Aimed at Reducing Pelagic Longline Interactions with Marine Turtles Yonat Swimmer, University of Hawaii Richard Brill, National."— Presentation transcript:

1 Physiology Experiments Aimed at Reducing Pelagic Longline Interactions with Marine Turtles Yonat Swimmer, University of Hawaii Richard Brill, National Marine Fisheries Service Mike Laurs, National Marine Fisheries Service

2 Increased Longline Fishing = Increased Catch Rates

3 Hard-shelled turtles Generally hooked Federally threatened Soft-shelled turtle Generally entangled Federally endangered

4 Research Needed 1) Determine impact (e.g. survivorship) of turtles captured and released from longline fishing gear. 2) Determine tactic(s) to keep turtles out of longline gear to develop “turtle-safe” fishing methods.

5 Survivorship studies summary: Use of Pop-up Satellite Archival Tags Two turtles tagged in Hawaii LL fishery (1 survived 4.5 months) 7 turtles tagged in Costa Rica (4 LL-caught, 3 controls) 5 of 6 LL-caught turtles survived a min. 5 weeks post-release. Need more data to estimate survivorship!

6 Research Needed 1) Determine impact (e.g. survivorship) of turtles captured and released from longline fishing gear. 2) Determine tactic(s) to keep turtles out of longline gear to develop “turtle-safe” fishing methods.

7 Sensory Physiology Research 1)Visual capabilities in targeted species (e.g. tuna, swordfish) and marine turtles 2)Behavioral responses to visual cues in marine turtles (e.g. lightsticks) 3)Molecular components of vision and olfaction in marine turtles 4)Hearing capabilities in turtles and tuna 5)Behavioral responses to bait modifications

8 Captive sea turtles: Green- Honolulu, Hawaii Loggerhead-Galveston, Texas Tunas and billfish: Honolulu, Hawaii Port Lincoln, Australia On board NOAA vessels

9 1) Vision: Turtles and Pelagic Fish lMarked differences found in the speed of vision and sensitivity to light in swordfish and tuna retinas (large day-night differences). lHave established the first scientific evidence for the basis of color vision in a billfish, the striped marlin. lPrevious studies indicate high visual acuity in sea turtles, and preliminary findings suggest that turtles also likely to show similar strong adaptations to night and day.

10 2) Behavior: Lightstick Color Preliminary results indicate that juvenile loggerhead sea turtles are attracted to conventional green lightsticks. Additional colors and brightness of electronic lightsticks to be tested.

11 Green Light Sticks Appear to Attract Juvenile Loggerhead Turtles

12 3) Molecular Components of Olfaction Sea turtles have a functional sense of smell with 30% functional odor receptor genes (vs. zero in marine mammals). Genetics work suggests olfactory system of sea turtles is closer to mammals, birds and frogs than fish.

13 4) Hearing: Turtles and Tunas Sea turtles detect a frequency range of Hz, with best hearing between Hz. Research in Italy suggests that loggerhead turtles may avoid sound sources of Hz. Tunas have best hearing over similar, but narrower ( Hz), frequency range. Little likelihood that ‘sound’, e.g., pingers, may be developed to deter sea turtles.

14 5) Bait modification research Must determine what attracts sea turtles to bait. Likely cues: Visual ? Chemical (e.g. olfactory) How can we use this information to repel turtles from bait??? *How can we use information to

15 Visual cues: Can food color attract or deter turtles?  Behavior Studies: –Kemp’s ridley (Fontaine et al., 1985) –Loggerhead (Higgins et al., on-going research ) –Green (Swimmer et al., on-going research)  Red-colored food items selected first!!

16 Can Food Color Deter Feeding?? Initial Avoidance to Blue-Dyed Foods: Kemp’s Ridley Green Loggerhead

17 Green Turtles Bait Preference Experiments Green turtles rejected blue dyed squid for up to 8 to 10 days, after that both blue and untreated squid readily eaten Untreated Squid Blue Dyed Squid

18 After 4 presentations, 33% turtles still don’t eat blue squid Loggerhead Turtles

19 Potential Feeding Deterrents (rely on taste/smell) Bitter substances Lactic and citric acid Urea Squid ink Garlic Jabanero chili extract Cilantro »Turtles and tunas ate all!!!

20 Natural defenses as potential deterrents Aplysia sp. ink

21 Olfactory Cues: Turtles capable of underwater chemoreception e.g. Walker 1959; Carr 1972; Manton et al. 1972, Navigation to natal Beaches via olfactory Cues (Carr 1972)

22 Olfaction Behavior study: Artificial Bait Masks visual differences Can determine importance of smell/taste Turtles prefer bait made of recognized food items. Data suggest that smell/taste important in turtle’s decision to bite bait

23 Summary & Future Plans Behavior studies suggest a visual deterrent (e.g. blue dyed bait, colored light sticks) may deter turtles from bait, but perhaps not as a long-term solution. Behavior and molecular studies indicate turtles’ reliance upon olfactory cues, suggesting the possibility for an effective odor-emitting bait modification. Acoustic studies suggest slight chance that sound stimuli may be used to repel turtles from longlines. Continue search for a “magic potion” (chemical or visual) to repel turtles from bait.

24 Acknowledgements University of Hawaii National Marine Fisheries Service Pelagic Fisheries Research Program L. Mailloux, D. Gremminger, G. Balazs


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