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ISRA FACTSHEETS

ASIA REGION

ISRA FACTSHEETS

ASIA REGION

Eight Mile Rock ISRA

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Eight Mile Rock ISRA

Eight Mile Rock

Summary

Eight Mile Rock is located in the Andaman Sea of southern Thailand. It is an underwater pinnacle covered with dense soft corals, from ~12 to 45 m depth. The area is situated within the Tarutao National Park. Within this area there are: threatened species (e.g., Whale Shark Rhincodon typus) and undefined aggregations (e.g., Sicklefin Devil Ray Mobula tarapacana).

Eight Mile Rock

Eight Mile Rock

DESCRIPTION OF HABITAT

Eight Mile Rock is located south of Adang Island in the Andaman Sea of southern Thailand. Eight Mile Rock is an underwater pinnacle with frequent strong currents and occasional upwelling. The top of Eight Mile Rock starts at ~12–15 m depth depending on the tide and descends to ~45 m depth. The pinnacle is covered in dense soft corals (Forra Diving pers. comm. 2024).

In the Andaman Sea, the circulation near the coasts and islands is mainly driven by equatorial forces. These significantly induce changes in water circulation during the monsoon-transition periods (April to May and October to November) and can result in upwelling (Chatterjee et al. 2017).

Eight Mile Rock falls within the Tarutao National Park.

This Important Shark and Ray Area is benthopelagic and is delineated from inshore and surface waters (0 m) to 45 m based on the bathymetry of the area.

CRITERION A

VULNERABILITY

Two Qualifying Species considered threatened with extinction according to the IUCN Red List of Threatened Species regularly occur in the area. These are the Endangered Whale Shark (Pierce & Norman 2016) and Sicklefin Devil Ray (Marshall et al. 2022).

CRITERION C

SUB-CRITERION C5 – UNDEFINED AGGREGATIONS

Eight Mile Rock is an important area for undefined aggregations of one shark and one ray species.

Whale Sharks have been observed aggregating around Eight Mile Rock for >15 years (between 2009–2024; U Lawoi [compressor diver] pers. comm. 2024). Fishers set and retrieve traps every two weeks through compressor diving and have reported seeing Whale Sharks year-round on 90% of visits to the area. This corresponds to ~360 observations over a 15-year period. Eight Mile Rock is particularly important as Whale Sharks are only infrequently observed at sites outside of the area, around Adang, Rawi, and Tarutao (S Pramongkij & U Lawoi [compressor divers] pers. comm. 2024). There were an additional 93 observations of Whale Sharks at Eight Mile Rock between 2006–2021 (MCRRDI 2021). Fifty-three (57%) of these observations were of more than one individual, with groups sizes ranging 1–5 individuals. Aggregations of five Whale Sharks were observed seven times between 2006–2021.

Anecdotal reports have confirmed that aggregations of Sicklefin Devil Rays have been observed in the area for >15 years (between 2009–2024; U Lawoi [compressor diver] pers. comms. 2024). Crowd sourced data from the dive community support anecdotal evidence of aggregations in this area, with 15 confirmed sightings between 2020–2022 (Thai Sharks and Rays unpubl. data 2024). Half of these sightings were of more than one individual, with a maximum group size of ~20 individuals. Four observations of aggregations from the area were also reported in 2003, 2014, 2016, and 2020 (DMCR unpubl. data 2021).

These species may be aggregating for feeding purposes as there are occasional observations of feeding behaviour when the water is visibly green from the presence of plankton. However, further information is required to confirm the nature and function of these aggregations.

Eight Mile Rock

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