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Unmanned Aerial Vehicles (UAVs) to compare foraging sea turtle density and distribution of sea turtles in two contrasting habitats in the Chagos Archipelago / CARINA REES

Swansea University Author: CARINA REES

Abstract

Unmanned Aerial Vehicles (UAVs) facilitate observation of elusive species or remote locations, and are increasingly used to survey marine habitats. Marine Protected Areas (MPAs) are a conservation tool used to protect marine species, and regular population assessments can establish if MPAs are effec...

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Published: Swansea 2022
Institution: Swansea University
Degree level: Master of Research
Degree name: MRes
Supervisor: Esteban, Nicole
URI: https://cronfa.swan.ac.uk/Record/cronfa59715
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spelling 2022-03-28T14:46:55.8964697 v2 59715 2022-03-28 Unmanned Aerial Vehicles (UAVs) to compare foraging sea turtle density and distribution of sea turtles in two contrasting habitats in the Chagos Archipelago c644b7d83aa67fc122eba901df0984a8 CARINA REES CARINA REES true false 2022-03-28 Unmanned Aerial Vehicles (UAVs) facilitate observation of elusive species or remote locations, and are increasingly used to survey marine habitats. Marine Protected Areas (MPAs) are a conservation tool used to protect marine species, and regular population assessments can establish if MPAs are effectively facilitating the recovery of endangered species. Sea turtles in the Western Indian Ocean have been historically exploited through trade and by-catch causing a reduction in numbers. Here, UAVs were utilised to assess the population density and distribution of green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles between ocean and lagoon environments in the Chagos Archipelago. Analysis protocols were developed to process UAV imagery, including carapace-measurement techniques, and certainty-classing turtle observations (Definite, Probable or Possible). Along 20 km of coastline, 5.13 km2 was surveyed across 11 days between July 2019 – February 2021 resulting in a high-certainty estimate of 381 turtles and a low-certainty estimate of 660. Species and life-stage identification implicate Chagos as developmental habitat for immature hawksbill turtles: 78.47% (n = 299/381) of identified definite turtles were immature, of which 66.55% (n = 199/299) were hawksbill. Diego Garcia Ocean Site 1, West sites and Turtle Cove were significant turtle hotspots (high-certainty results: 257.19 individuals/km2, 146.15 individuals/km2, and 135.08 individuals/km2, respectively), while Marina sites were least-dense (0 - 4.87 individuals/km2). Results for low-certainty data were comparable: 325.27 individuals/km2 in Diego Garcia Site 1, followed by 309.27 and 292.67 individuals/km2 in Turtle Cove. Population density decreased significantly with increasing distance from the shore, and decreased with increasing distance from Turtle Cove. Green turtles were smaller (50.33 ± 17.65 cm straight-carapace length, SCL) than hawksbill turtles (53.16 ± 11.17 cm SCL). This study highlights the Chagos Archipelago as developmental habitat for immature turtles, and demonstrates the applicability of UAVs for in-situ population monitoring to infer conservation status of marine megafauna. E-Thesis Swansea Unmanned Aerial System, drone survey, marine turtle, endangered species, population monitoring 11 3 2022 2022-03-11 COLLEGE NANME COLLEGE CODE Swansea University Esteban, Nicole Master of Research MRes 2022-03-28T14:46:55.8964697 2022-03-28T14:31:59.5033528 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Biosciences CARINA REES 1 59715__23691__f55e729d793f411d8204a6f187fbc7ee.pdf Rees_Carina_MRes_Thesis_Final_Redacted_Signature.pdf 2022-03-28T14:41:21.2424784 Output 2569090 application/pdf E-Thesis – open access true Copyright: The author, Carina Rees, 2022. true eng
title Unmanned Aerial Vehicles (UAVs) to compare foraging sea turtle density and distribution of sea turtles in two contrasting habitats in the Chagos Archipelago
spellingShingle Unmanned Aerial Vehicles (UAVs) to compare foraging sea turtle density and distribution of sea turtles in two contrasting habitats in the Chagos Archipelago
CARINA REES
title_short Unmanned Aerial Vehicles (UAVs) to compare foraging sea turtle density and distribution of sea turtles in two contrasting habitats in the Chagos Archipelago
title_full Unmanned Aerial Vehicles (UAVs) to compare foraging sea turtle density and distribution of sea turtles in two contrasting habitats in the Chagos Archipelago
title_fullStr Unmanned Aerial Vehicles (UAVs) to compare foraging sea turtle density and distribution of sea turtles in two contrasting habitats in the Chagos Archipelago
title_full_unstemmed Unmanned Aerial Vehicles (UAVs) to compare foraging sea turtle density and distribution of sea turtles in two contrasting habitats in the Chagos Archipelago
title_sort Unmanned Aerial Vehicles (UAVs) to compare foraging sea turtle density and distribution of sea turtles in two contrasting habitats in the Chagos Archipelago
author_id_str_mv c644b7d83aa67fc122eba901df0984a8
author_id_fullname_str_mv c644b7d83aa67fc122eba901df0984a8_***_CARINA REES
author CARINA REES
author2 CARINA REES
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publishDate 2022
institution Swansea University
college_str Faculty of Science and Engineering
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hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Biosciences, Geography and Physics - Biosciences{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Biosciences
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description Unmanned Aerial Vehicles (UAVs) facilitate observation of elusive species or remote locations, and are increasingly used to survey marine habitats. Marine Protected Areas (MPAs) are a conservation tool used to protect marine species, and regular population assessments can establish if MPAs are effectively facilitating the recovery of endangered species. Sea turtles in the Western Indian Ocean have been historically exploited through trade and by-catch causing a reduction in numbers. Here, UAVs were utilised to assess the population density and distribution of green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles between ocean and lagoon environments in the Chagos Archipelago. Analysis protocols were developed to process UAV imagery, including carapace-measurement techniques, and certainty-classing turtle observations (Definite, Probable or Possible). Along 20 km of coastline, 5.13 km2 was surveyed across 11 days between July 2019 – February 2021 resulting in a high-certainty estimate of 381 turtles and a low-certainty estimate of 660. Species and life-stage identification implicate Chagos as developmental habitat for immature hawksbill turtles: 78.47% (n = 299/381) of identified definite turtles were immature, of which 66.55% (n = 199/299) were hawksbill. Diego Garcia Ocean Site 1, West sites and Turtle Cove were significant turtle hotspots (high-certainty results: 257.19 individuals/km2, 146.15 individuals/km2, and 135.08 individuals/km2, respectively), while Marina sites were least-dense (0 - 4.87 individuals/km2). Results for low-certainty data were comparable: 325.27 individuals/km2 in Diego Garcia Site 1, followed by 309.27 and 292.67 individuals/km2 in Turtle Cove. Population density decreased significantly with increasing distance from the shore, and decreased with increasing distance from Turtle Cove. Green turtles were smaller (50.33 ± 17.65 cm straight-carapace length, SCL) than hawksbill turtles (53.16 ± 11.17 cm SCL). This study highlights the Chagos Archipelago as developmental habitat for immature turtles, and demonstrates the applicability of UAVs for in-situ population monitoring to infer conservation status of marine megafauna.
published_date 2022-03-11T04:17:14Z
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