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ISRA FACTSHEETS

ASIA REGION

ISRA FACTSHEETS

ASIA REGION

Heliana Island ISRA

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Heliana Island ISRA

Heliana Island

Summary

Heliana Island is one of the southernmost islands in Indonesia. It is located off Rote Island in the Rote Ndao Regency, East Nusa Tenggara Province. The area is characterised by mangrove forests, coral reefs, and sand and mud substrates. It is influenced by monsoons. This area overlaps with the Rote Barat Daya Key Biodiversity Area. Within this area there are: threatened species and undefined aggregations (Oceanic Manta Ray Mobula birostris).

Heliana Island

Heliana Island

DESCRIPTION OF HABITAT

Heliana Island is one of the southernmost islands in Indonesia. It is located off Rote Island in the Rote Ndao Regency, East Nusa Tenggara Province. Heliana Island is situated in the Heliana-Bo’a channel, between Rote Island and Ndana Island. It is characterised by mangrove forests, coral reefs, and muddy and sandy substrates (Widiatmaka et al. 2016). The area is influenced by monsoons: the southeast monsoon (from April to November) has low precipitation, and the northwest monsoon (from December to March) has high precipitation (Verbelen et al. 2017).

This area overlaps with the Rote Barat Daya Key Biodiversity Area (KBA 2024).

This Important Shark and Ray Area is benthopelagic and delineated from inshore and surface waters (0 m) to 60 m based on the depth range of Qualifying Species in the area.

CRITERION A

VULNERABILITY

One Qualifying Species within the area is considered threatened with extinction according to the IUCN Red List of Threatened Species. The Oceanic Manta Ray is assessed as Endangered (Marshall et al. 2022).

CRITERION C

SUB-CRITERION C5 – UNDEFINED AGGREGATIONS

Heliana Island is an important area for undefined aggregations of one ray species.

Oceanic Manta Rays were observed engaging in cleaning behaviour during four recreational dives between September and November 2023 (Thrive Conservation unpubl. data. 2024). Based on extensive surveys, Heliana Island is the first-choice cleaning station within surrounding waters (N Ichida pers. obs. 2024). The cleaning station is particularly small, and as Oceanic Mantas here are large-bodied, there is no space for more than a couple of individuals to be present around the bommie at any one time. Smaller bommies in adjacent waters are used as an ‘overflow’ for when the cleaning station at Heliana Island is being used simultaneously by too many individuals (S Lewis pers. obs. 2024). Oceanic Manta behaviour here and elsewhere is such that they ‘take turns’ at the cleaning station. Whilst one Oceanic Manta is using the cleaning station, other individuals circle the station from a distance or use the ‘overflow’ until they come back to this bommie. However, up to six individuals have been observed using the cleaning station within a single day (Thrive Conservation unpubl. data. 2024).

At Heliana Island, Oceanic Manta Rays are cleaned by Bluestreak Cleaner Wrasse Labroides dimidiatus, Moon Wrasse (genus Thalassoma), and False Moorish Idol Heniochus diphreutes (Thrive Conservation unpubl. data. 2024). Cleaning behaviour of Oceanic Manta Rays was recorded in 26% of 119 dive surveys undertaken between April 2017 and October 2019 (Thrive Conservation unpubl. data. 2024). Remote GoPro cameras (camera traps) were placed at the cleaning station opportunistically 82 times, and recreational dive observations were conducted 37 times. Oceanic Manta Rays were present on 46 occasions (39%) with 1–6 individuals (mean = 2) being observed (of which 80% were male). A total of 28 Oceanic Manta Rays were photo-identified with at least two recurring individuals. Heliana Island is the only known Oceanic Manta Ray cleaning station in the greater Savu Sea region (Thrive Conservation unpubl. data. 2024), and outside of Raja Ampat and Fakfak (MV Erdmann pers. obs. 2024; S Lewis pers. obs. 2024).

Heliana Island

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