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ISRA FACTSHEETS

ASIA REGION

ISRA FACTSHEETS

ASIA REGION

Blongas ISRA

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Blongas ISRA

Blongas

Summary

Blongas is located off Lombok, Indonesia. It is characterised by a large rock pinnacle with steep walls surrounded by deep waters. The area is influenced by strong currents, surges, and downdrafts. Within this area there are: threatened species (e.g., Reef Manta Ray Mobula alfredi) and undefined aggregations (e.g., Scalloped Hammerhead Sphyrna lewini).

Blongas

DESCRIPTION OF HABITAT

Blongas is located to the south of Lombok, Indonesia. The area is characterised by the pinnacle of a submerged platform that slopes steeply into deeper waters. The rock pinnacle rises from ~60–80 m depth (IndonesiaDive 2022; LiveAboardIndonesia 2024). The area is also known as Belongas Bay or ‘The Magnet’ by the recreational dive community.

The area is influenced by strong currents (IndonesiaDive 2022), surges, and potential downdrafts (IndopacificImages 2024). The water temperature can drop to 21–24°C (IndonesiaDive 2022). The area has low visibility, reportedly due to the high nutrient level in the water (ScubaBoard 2017).

This Important Shark and Ray Area is pelagic and is delineated from surface waters (0 m) to 400 m based on the depth range of the Qualifying Species in 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 Critically Endangered Scalloped Hammerhead (Rigby et al. 2016) and the Vulnerable Reef Manta Ray (Marshall et al. 2022).

CRITERION C

SUB-CRITERION C5 – UNDEFINED AGGREGATIONS

Blongas is an important area for undefined aggregations of one shark and one ray species.

Based on citizen science reports from dive centres operating in Blongas and other recreational divers, aggregations of >100 Scalloped Hammerheads are regularly and predictably recorded around the island (MV Erdmann pers. obs. 2024). Aggregations are supported by a photograph of 70 individuals, and by photographs/videos of up to 20 individuals. There are also contemporary anecdotal reports of Scalloped Hammerhead aggregations in the area from October 2009 (Bottles Up Diving 2024), September 2011 (ScubaBoard 2011), and September 2012 (TripAdvisor 2012), as well as a historical report from ~2008 (ScubaBoard 2010). Aggregations are seasonal between June and the end of October. The regularity and predictability of the aggregations are demonstrated through historical and contemporary records, however, further information is needed to confirm the nature and function of these aggregations.

Based on information from dive centres operating in Blongas, and other recreational divers, aggregations of >40 Reef Manta Rays are regularly and predictably recorded around the island (MV Erdmann pers. obs. 2024). Documented records include aggregations of up to six individuals in August 2020, up to 40 individuals on 21 July 2022, and >15 individuals on 15 August 2023 and 19 August 2023. Aggregations are often reported from the ‘Manta Pot’ dive site within the area, at ~12–14 m depth. Reef Manta Rays may be using this area for cleaning purposes, or based on the recorded behaviour, Reef Manta Rays may be attracted to Blongas because of the high nutrient level inferred from the green hue of the water (ScubaBoard 2017). Additional information is needed to confirm the nature and function of these aggregations.

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