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ISRA FACTSHEETS

NEW ZEALAND & PACIFIC ISLANDS REGION

ISRA FACTSHEETS

NEW ZEALAND & PACIFIC ISLANDS REGION

Tanna ISRA

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Tanna ISRA

Tanna

Summary

Tanna is located on the southeast of the island of Tanna in Vanuatu. The area, known locally as ’Shark Bay’, is characterised by an enclosed tidal bay surrounded by high cliffs. The substrate is comprised of warm dark sand and underwater hot waterspouts owing to the volcanic activity on the island. Within the area there are: threatened species and reproductive areas (Blacktip Reef Shark Carcharhinus melanopterus).

Tanna

Tanna

DESCRIPTION OF HABITAT

Tanna is located on the southeast of the island of Tanna in Vanuatu. The area, known locally as ’Shark Bay’, is characterised by an enclosed tidal bay, surrounded by high cliffs. The substrate is comprised of warm dark sand and underwater hot waterspouts owing to the volcanic activity on the island (Tanna Adventures 2024). 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 to February (Walshe et al. 2017).

This Important Shark and Ray Area is benthic and pelagic and is delineated from inshore and surface waters (0 m) to 20 m based on the bathymetry of the area.

CRITERION A

VULNERABILITY

One Qualifying Species considered threatened with extinction according to the IUCN Red List of Threatened Species regularly occurs in the area. This is the Vulnerable Blacktip Reef Shark (Simpfendorfer et al. 2020).

CRITERION C

SUB-CRITERION C1 – REPRODUCTIVE AREAS

Tanna is an important reproductive area for one shark species.

Neonate and young-of-the-year (YOY) Blacktip Reef Sharks have been reported to aggregate in the area. Blacktip Reef Sharks come into the bay in large numbers, particularly in the cooler months of the year (June–August), for the warmth caused by underwater hot waterspouts located in the bay (Tanna Adventures 2024). Citizen science reports reveal footage of small (visually estimated >60 cm total length [TL]) Blacktip Reef Sharks from 2019–2021, with up to six individuals observed in a single frame (Trip Advisor 2024a, You Tube 2024). Animals are best viewed on the low tide in the area (Trip Advisor 2024a). Size-at-birth for this species is 30–52 cm TL (Ebert et al. 2021), indicating the observed sharks were neonates and/or YOY. Despite a lack of dedicated survey data from the area, the habitat is consistent with the ecological preference of young Blacktip Reef Sharks which are known to prefer shallow, sheltered waters (George et al. 2019), and maintain small home ranges at early life stages (Bouyoucos et al. 2021).

An online search revealed only two records of Blacktip Reef Sharks from elsewhere in Vanuatu, around the main island of Efate (Flickr 2024, Trip Advisor 2024). There are no records on iNaturalist of Blacktip Reef Sharks from Vanuatu waters and only one record of a shark or ray species from the western side of the island of Tanna (an Oceanic Fantail Ray in 2011). The paucity of online records of this species in Vanuatu highlights the relative importance of the area for reproduction in Blacktip Reef Sharks.

Tanna

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