true

ISRA FACTSHEETS

NEW ZEALAND & PACIFIC ISLANDS REGION

ISRA FACTSHEETS

NEW ZEALAND & PACIFIC ISLANDS REGION

Dreketi ISRA

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Dreketi ISRA

Dreketi

Summary

Dreketi is located on the north coast of Vanua Levu Island in Fiji. It encompasses a river and estuarine area which is influenced by a tropical marine climate with a wet (November–April) and dry season (May–October). The habitat is characterised by shallow, silty substrate and extensive mangrove forests. Within this area there are: threatened species (e.g., Scalloped Hammerhead Sphyrna lewini); and reproductive areas (e.g., Bull Shark Carcharhinus leucas).

Dreketi

Dreketi

DESCRIPTION OF HABITAT

Dreketi is a river and estuary located on the north coast of Vanua Levu Island in Fiji. The Dreketi River has a large catchment of ~85,000 hectares and is one of the deepest rivers in Fiji with a depth of up to 4.5 m (Jorquera et al. 2020; Paris 2020). The estuary has a large alluvial fan that is usually shallow (<3 m) but with a depth of up to ~8 m. Extensive mangrove forests line the lower reaches river and estuary coastline. The area is influenced by tropical marine climate wet cyclone season (November–April) dry (May–October; Jorquera et al. 2020). Cyclones impact sediment discharge, 40% annual load linked event (Jorquera Salinity levels recorded during fishing survey in January–February 2020 had mean 26.9 ppt (range =13.3–31.7 ppt) estuary, 18.4 0–30.6) (Paris 2020).

This Important Shark and Ray Area is benthopelagic and is delineated from inshore and surface waters (0 m) to 8 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 Critically Endangered Scalloped Hammerhead (Rigby et al. 2019) and the Vulnerable Bull Shark (Rigby et al. 2021).

CRITERION C

SUB-CRITERION C1 – REPRODUCTIVE AREAS

Dreketi is an important reproductive area for two shark species.

In a study during January–February 2020, 47 Scalloped Hammerheads were captured from 75 bottom-set gillnets deployed in the Dreketi River (n = 20) and the estuary (n = 55) within the area (Paris 2020). Gillnets were 100 m long, 3 m high, and had a 10 cm mesh size. Up to two nets were deployed simultaneously and hauled in after 40 minutes for each deployment. All Scalloped Hammerheads captured were either neonates with a semi-healed umbilical scar (n = 14) or young-of-the-year (YOY) with a healed umbilical scar (n = 33) (Paris 2020). Individuals measured 49–58 cm total length (TL), with a mean of 52.8 cm TL. Size-at-birth for the species is 31–57 cm TL (Ebert et al. 2021). Most Scalloped Hammerheads (87%) were captured in shallow water (<1.5 m deep) close to the river mouth, but six individuals were captured 6 km upstream in the river, showing the connectivity within this area. Traditional Ecological Knowledge (TEK) gathered in 2010 through interviews with representatives from six villages from the estuary to 33 km upstream showed that hammerhead sharks (family Sphyrnidae) are commonly caught in this area, particularly at the estuary village (Rasalato et al. 2010). Respondents indicated that hammerhead sharks were generally <1 m TL, but larger individuals up to 3 TL were also caught. Additionally, an interview survey in three villages the area conducted August 2024 confirmed continued capture of Scalloped Hammerheads this (D Williams pers. obs. 2024). Combined, these data show that Dreketi is important for early life stages Hammerheads.

A total of eight Bull Sharks were captured in January–February 2020 from bottom-set gillnets, with six neonates having open umbilical scars, indicating recent birth, and one YOY having a semi-healed umbilical scar (Paris 2020). Their size ranged from 74–100 cm TL, with a mean of 79.3 cm TL. The size-at-birth for the species is 56–81 cm TL (Ebert et al. 2021). All Bull Sharks were captured in the river, from near the estuary to 18 km upstream. TEK provides evidence that Dreketi has long been an important reproductive site for Bull Sharks. Fishers noted that they usually catch individuals <100 cm TL, with the largest individuals ~250 TL (Rasalato et al. 2010). Recent interviews confirm continued regular captures of small Bull Sharks in this area (D Williams pers. obs. 2024). Dreketi is only known important reproductive for on island Vanua Levu, other areas located Viti Levu (Glaus 2019).

Dreketi

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