THE SPATIAL DYNAMICS OF SEA TURTLES WITHIN FORAGING GROUNDS ON ELEUTHERA, THE BAHAMAS

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1 Earthwatch 2016 Annual Field Report TRACKING SEA TURTLES IN THE BAHAMAS THE SPATIAL DYNAMICS OF SEA TURTLES WITHIN FORAGING GROUNDS ON ELEUTHERA, THE BAHAMAS Annabelle Brooks, MSc REPORT COMPLETED BY: Annabelle Brooks, Cape Eleuthera Institute PERIOD COVERED BY THIS REPORT: February November

2 Dear volunteers, Thank you so much for helping make 2016 a successful year for this study. Your efforts were vital in collecting a vast amount of data also allowed us to see some incredible things in the field. Field work was a very exciting and rewarding time we have now caught a total of 487 turtles! 2016 also marked a new chapter for the sea turtle research program. Evidence of poaching at field sites in 2015 encouraged us to address the lack of awareness and enforcement of the sea turtle harvest ban and we began a new collaboration with the Bahamas Department of Marine Resources to address this problem. Since then we co-founded the Bahamas Sea Turtle Network in March 2016 and the data collected by volunteers will allow for long term population trends that will help determine if the harvest ban is an effective conservation measure. The existence of this project also made it possible for school children from Eleuthera and Nassau see sea turtles up close and learn more about their ecology and the importance of their conservation. The staff of the Cape Eleuthera Island School also ventured into the field and experienced a day in the life of an Earthwatch volunteer; they were thrilled! These individuals are now part of the wider community like yourselves who advocate for sea turtle conservation and the habitats they exist in. I thank you again for supporting this important work. Sincerely, 2

3 Summary We have gained insight into the seasonal trends of sea turtles and their predators and are able to start addressing some of the larger questions posed by this project. We also achieved a seasonal assessment of the food availability within sea turtle foraging grounds. Now we have completed the third year of research in 2016, the large data set compiled will be analysed and the insight gained will be ready to publish. Goals, Objectives, and Results Objective 1: Monitoring Sea Turtle Abundance and Distribution: We now have 3 years worth of abundance survey data that shows distinct variation in abundance and distribution of green sea turtles. There are some clear drivers of foraging ground suitability emerging. Figure 1. The mean number of juvenile green sea turtles observed during creek abundance surveys over the course of Values above bars indicate the specific number of surveys conducted in each creek. 3

4 Objective 2: Monitoring Habitat and Resource Availability: We completed a full year of seasonal benthic habitat mapping and have gained a more detailed understanding of the seagrass community in the foraging sites of our sea turtles. Figure 2: Average seagrass biomass in terms of dry weight per meters squared of three seagrass species found in different study sites in spring of Objective 3: Assessing Predation Risk: Having completed our final year of BRUV surveys we have gained insight into the levels of predation that sea turtles are facing and hope to correlate with the scars and injuries seen. Predation appears to be relatively low, with tiger sharks being seen only in a few locations and mostly juvenile. 4

5 Figure 3. Proportion of green sea turtles that were caught with signs of surviving a predation within each creek. Values at the top of each bar indicates the total number of turtles caught. Grey portion represents the percentage of turtles that display signs of predation. The values in the grey region corresponds to the respective predation percentages. Objective 4: Long-term monitoring: We have vastly expanded our database and been able to recapture many individuals. This provides us the opportunity to determine site fidelity and growth rates. Despite variation across our study sites, the mean growth rate is consistent with other studies in the Bahamas. Our size ranges show that we have turtles that have recently recruited but that they leave Eleuthera around the 60cm size class, which is still sub-adult. We have found a lot of variation in health also, within sites and between sites and is an area of further research. 5

6 Figure 4. The number of juvenile green sea turtles tagged and the number of turtles that were recaptured after being tagged. Half Sound has the largest number of turtles that have been tagged and recaptured at n=230 and n=47, respectively. Tagging dates began in Figure 5. Mean growth rate (GR) of juvenile green sea turtles derived from straight carapace length n- t (SCL n-t) measurements of recaptured turtles in each creek since Values above bars indicate the number of growth rate measurements obtained from recaptured juvenile green sea turtles within their respective creeks. There are no significant differences in GR of green turtles between creeks. 6

7 Figure 6. Length frequency graph derived from straight carapace length n-t (SCL n-t) measurement. Of the 268 turtles measured, 45.9% fall within the size classes of 280mm-360mm. Figure 7. Relationship between juvenile green sea turtle straight carapace length (mm) and weight (kg). 7

8 Project Impacts Report contributions in the categories below for the past fielding year. 1. Increasing Scientific Knowledge a. Peer-reviewed publications Fisheries & Conservation Management in The Bahamas: Shifting Paradigms of Fisheries Management & Conservation in The Bahamas. In prep. Home Range and Habitat Use of Immature Green Sea Turtles in a Shallow, Tidal Foraging Ground. In prep. A review of Fibropapillomatosis in The Bahamas. In prep. b. Non-peer reviewed publications: Technical reports, white papers, articles, sponsored or personal blogs c. Presentations : Brooks, A, Miller, R, Kincaid, K Assessing the knowledge and perceptions of Bahamians concerning sea turtles and their conservation. Bahamas National History Conference, Nassau Bahamas. March Miller, R, Kincaid, K, Brooks, A Assessing the knowledge and perceptions of Bahamians concerning sea turtles and their conservation. 36 th Annual Symposium on Sea Turtle Biology and Conservation, Lima, Peru. February Mentoring a. Graduate students list graduate students doing thesis work on the project Student Name Graduate Degree Project Title Anticipated Year of Completion Meagan Gary MSc. Home Range and Habitat Use of Immature Green Sea Turtles in a Shallow, Tidal Foraging Ground 2016 b. Community outreach provide details on how you have supported the development of environmental leaders in the community in which you work. Name of school, organization, or group Education level Participants local or non-local Details on contributions/ activities Deep Creek Middle School Middle School Local 12 students assisted in capturing and tagging, sea turtle class 8

9 Dunmore Academy Middle School Local 8 students assisted in capturing and tagging, seagrass class Eco Club of Eleuthera Middle/Highschool Local 23 students assisted in capturing and tagging Public servants outreach Nurses Local Gave information and observed turtle work up and tagging (2) 3. Partnerships list your current active professional partnerships that contribute to your project Partner Support Type(s) 1 Years of Association (e.g present) University of Florida Family Island Research and Education Disney Conservation Fund Technical/academic support, collaboration Technical/academic support, collaboration Funding 2012-present 2012-present present 4. Contributions to management plans or policies - list the management plans/policies to which your project contributed this year Plan/Policy Name Type 2 Level of Impact 3 New or Existing? Primary goal of plan/policy 4 Stage of plan/policy 5 Description of Contribution Antipoaching Agenda national New Species conservation, natural resource conservation In progress Partnering with Department of Marine Resources, Bahamas National Trust, Bahamas Reef Environment Education Foundation, Archie Carr Center for Sea Turtle Research, to provide educational support and data for a sea turtle awareness and antipoaching campaign. Acknowledgements I m indebted to my team of interns, technicians, and research assistants. I also appreciate the support of Stevie Connett and Barbara Crouchley with field work and advice, and Dr. Karen Bjorndal and Dr. Alan Bolten for their time and support with all aspects of this study. I would also like to thank the boathouse team for keeping us on the water and the kitchen team for keeping us well fed! 9