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ISRA FACTSHEETS

NEW ZEALAND & PACIFIC ISLANDS REGION

ISRA FACTSHEETS

NEW ZEALAND & PACIFIC ISLANDS REGION

Oyster Island ISRA

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Oyster Island ISRA

Oyster Island

Summary

Oyster Island is located on the eastern side of Espiritu Santo Island in Vanuatu. It is a shallow reef area, characterised by sandy substrate and coral reefs. The area is subject to strong southeasterly winds, large swells, and warm water temperatures (29–30°C). Within the area there are: threatened species (e.g., Blotched Fantail Ray Taeniurops meyeni) and undefined aggregations (e.g., Porcupine Ray Urogymnus asperrimus).

Oyster Island

Oyster Island

DESCRIPTION OF HABITAT

Oyster Island is situated on the eastern side of Espiritu Santo Island in Vanuatu. It is a shallow reef area, characterised by sandy substrate and coral reefs. The coral substrates form ‘fingers’ up to 100 m long, stretching from the sandy shallows (~12 m depth) to ~25 m depth (M Burbeary pers. obs. 2024). Between the coral reef fingers (~5–30 m apart) are stretches of sandy substrate.

The climate in Vanuatu is characterised by high rainfall and high temperatures throughout the year, and experiences severe tropical cyclones during the austral summer months of December–February (Walshe et al. 2017). The area is subject to strong southeasterly winds, large swells, and seasonal red algae blooms owing to warm water temperatures (29–30°C; M Burbeary pers. obs. 2024).

This Important Shark and Ray Area is benthic and pelagic and is delineated from inshore and surface waters (0 m) to 25 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 Porcupine Ray (Sherman et al. 2024a) and the Vulnerable Blotched Fantail Ray (Sherman et al. 2024b).

CRITERION C

SUB-CRITERION C5 – UNDEFINED AGGREGATIONS

Oyster Island is an important area for undefined aggregations of two ray species.

Between January 2023 to August 2024, approximately 40 recreational dives were conducted in the area (M Burbeary pers. obs 2024).

During this period, over 20 sightings of Blotched Fantail Rays were reported from dives in the area (50% of dives). The majority of sightings (60%) were of rays actively foraging in the sandy substrate (M Burbeary pers. obs. 2024). The other sightings (40%) were of rays resting on the sand. Approximately 10 of the sightings were of more than one individual feeding (2–3 on average). Blotched Fantail Rays are seen occasionally at other dive sites around the islands off Espiritu Santo in Vanuatu, however, nowhere else with any regularity.

During the same period, over 20 sightings of Porcupine Rays (50% of dives) were recorded. The majority of sightings (80%) were of rays actively foraging in the sandy substrate (M Burbeary pers. obs. 2024). Most sightings were of individual rays, with two or more rays in close proximity to one another seen on 5–6 occasions. Porcupine Rays are not observed at any other dive sites around the Espiritu Santo islands in Vanuatu.

The mixture of sandy patches with coral substrates likely combine to create beneficial foraging opportunities to both Qualifying Species, however, more information is required to determine the nature and function of these aggregations.

Oyster Island

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