Yonat Swimmer, Richard Brill, Lianne Mailloux University of Hawaii VIMS-NMFS

Transcription

1 Survivorship and Movements of Sea Turtles Caught and Released from Longline Fishing Gear Yonat Swimmer, Richard Brill, Lianne Mailloux University of Hawaii VIMS-NMFS PFRP PI Workshop-2002

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

4 Question: What is fate of sea turtles post-release??

5 Pop-up satellite archival tags (PSATs) To determine post-release survivorship To determine post-release pelagic behavior (e.g. geolocation, dive depths/duration, migratory corridors) Deployed by at-sea observers

6 Why Use PSATs over conventional satellite transmitters? Cons Expensive Questionable geolocation data Delay in receiving data Difficult to attach to turtle Pros Can retrieve data in event of mortality!!

7 PSATs: Internal clock & sensors to record: *geographic location (via sunrise/sunset times) *dive depth, duration *temperature

8 How do we get the data? PSATs release at pre-set date... tags float to the surface... data transmitted to satellite data received on our computers.

9 When will PSATs float to surface? 1) At pre-set pop-up date 2) After tag has been at constant depth for 4 days* 3) After tag has exceeded 1,500 m depth* 4) If tag and/or baseplate are shed *these parameters exceed what is expected to occur in a live turtle (we assume mortality)

10 Attaching PSAT on a hard-shelled turtle Marine epoxy and syntatic foam base-plate

11 Marine epoxies to adhere base-plate to hard-shell turtles Easy to use Safe to use on boat (both for turtle and operator) Base-plate and tag will float if tag is shed prematurely

12 To better understand the impact of a turtle-longline encounter, PSAT data (e.g. survivorship & behavior) will be correlated with observations noted, such as: Hook location Severity of Injury Assessment of health

13 How do we know the system will work?? Lessons learned from a blue shark

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15 PSAT Blue Shark (Musyl & Brill) Depth/Temp Data Depth (ft) PSAT deployed Temp ( o C) Depth(ft) Temp(C) /10 4/11 4/12 4/13 4/14 4/15 4/16 4/17 4/18 4/19 4/20 0

16 PSATs in the Hawaii Longline Fishery Since March 2001, ~60 Scientific Technicians (Observers) trained to attach PSATs on hard shelled turtles HI: 21% coverage (each observer has tag kit) 2 turtles caught in LL gear and released with PSAT Olive Ridley, tracked for ~ 4 months Loggerhead, tag shed immediately

17 Geolocations determined by PSATs Based on raw data obtained from tag/satellite Most probable track predicted from state-space model via the Kalman filter [done by A. Nielsen]. - Each point on this track is computed as the weighted average of the model predictions from all other observations and the observation at the point.

18 Olive Ridley (13202): Hooked in mouth 1,874 n mi Pop-off location PSAT deployed ~ 4 months at liberty post-release

19 Olive Ridley (13202) Percentage Time at Depth Day and Night % frequecy Depth (m) Night Day Depth data suggest tag was shed rather than a mortality

20 Min-Max Depth for Olive ridley (13202) Depth (m) Aug. 15, 2001 Nov. 15, 2001 Time minimum maximum

21 Turtle s Movements and Oceanic Fronts Were oceanographic features associated with the turtle s movements? No correlations were found between turtle movements and temperature- and chlorophyllfronts. Data suggest turtle s horizontal movements were correlated with the Northern Equatorial currents. [Keith Bigelow]

22 Turtle Hawaiian Islands

23 Power of Tagging: What we learned from 1 Turtle Turtle survived min. 4 months post-release after deep hooking in mouth, swam nearly 1,900 nmi. Turtle spent nearly 60% of it s time within the top 50 m during day, remained deeper at night. Turtle did not exceed depths of 250 m, except on a few rare occasions. The maximum dive depth was recorded at 544 m, with a corresponding temperature of 4.0 o C. Turtle s horizontal movements appear correlated with the Northern Equatorial currents.

24 Depth (ft) 0 Depth (ft) for Loggerhead (CR 13107) PSAT deployed /30/02 5/02/02 5/04/02 5/06/02 5/08/02 5/10/02 5/12/02 5/14/02 5/16/02 No change in pressure suggests tag was shed immediately after release an attachment problem

25 3 Controls (free swimming) - 3 olive ridleys Costa Rica Sea turtles= 8% total catch longline fishery Collaboration: U. of Hawaii, NMFS, Sea Turtle Restoration Project 6 Caught and released from longline gear -5 olive ridleys, 1 green turtle

26 Horizontal Movements of 2 Turtles Hooked and Released from Longline Fishing Gear Turtles at liberty ~6 weeks

27 60 Olive Ridley deeply hooked in mouth Time at Depth Day and Night (CR 13198) % Frequency % Day Frequency % Night Frequency meters (6 weeks at liberty, 82 n mi straight distance)

28 Depth (Ft) 0 Deeply hooked in mouth Dive Depth (ft) for Olive Ridley (CR 13117) PSAT deployed /25/01 12/05/01 12/15/01 12/25/01 1/04/02 1/14/02 1/24/02 (6 weeks at liberty, 195 n mi straight distance)

29 Movements of 3 Free-Swimming (control) Turtles Turtles at liberty 6-8 weeks

30 Olive Ridley Free swimming control Time at Depth Day and Night (CR 13204) % Frequency % Day % Night meters (6 weeks at liberty, 477 n mi straight distance)

31 Depth (Ft) 0 Free-swimming control Dive Depth (ft) for Olive Ridley (CR 13112) PSAT deployed /25/01 12/05/01 12/15/01 12/25/01 1/04/02 1/14/02 1/24/02 2/03/02 2/13/02 2/23/02 (Two months at liberty)

32 Depth (Ft) 0 Free-swimming control Dive Depth (ft) for Olive Ridley (CR 13108) PSAT deployed /25/01 12/05/01 12/15/01 12/25/01 1/04/02 1/14/02 1/24/02 2/03/02 2/13/02 (Two months at liberty)

33 Summary of PSATs Deployed at Sea 1 of 2 PSATs deployed in Hawaii longline recorded data ~ 4 months. Data suggest tag shed rather than mortality. 5 of 7 PSAT deployed in Costa Rica shed early (6-8 weeks). Depth data suggest all tags were shed. Will investigate potential that hooked turtles remain more shallow (0-100m) than controls.

34 Efforts/collaborations to deploy PSATs on Longline-caught hard-shelled turtles Contract with PRETOMA in Costa Rica to continue observer coverage California longline-observer program trained in PSAT attachment Collaboration in planning to deploy PSATs in Brazilian longline fishery

35 Leatherbacks & PSATs Current attachment methods (e.g. harness) not feasible for at-sea application by observers Direct-carapace method tested on 5 nesting females (P.I: Molly Lutcavage. Puerto Rico, June 2002) Could ideally be refined for use by observers

36 Current Research Goals Determine source for early shedding of tags (PSAT or attachment??) Refine attachment procedures accordingly Continue extensive collaborations to increase tagging opportunities

37 Acknowledgements Funding and facilities provided by the National Marine Fisheries Service and the Pelagic Fisheries Research Program at the University of Hawaii. Collaborators include: NMFS observers and observer program, A. Nielsen, J. Sibert, R. Arauz, STRP, L. Mailloux, D. Gremminger, G. Balazs, M. Lutcavage, S. Sadove, A. Rhodin, Saltwater Inc., R. Morris, and T. Gorgas.