Threat assessment of the northern long-necked turtle Chelodina oblonga (chelidae) population in the Finniss River floodplain (northern Australia)

Abstract

The Northern Long-necked turtle Chelodina oblonga is considered Near Threatened under IUCN Red List criteria. In the Finniss River floodplain, the species is considered a potential source of protein for indigenous communities, which expressed concerns about the health and condition of the Northern Long-necked turtle. From May to October 2018, 15 areas were surveyed and 21 dead individuals were collected. The smallest and largest animals observed had carapace lengths of 121 mm and 253 mm, respectively. In September traditional owners from Bulgul community harvested four individuals and samples from fat, muscle and liver were collected for analysis. A map of distribution was created. Comprehensive literature review and interviews with traditional owners and turtle specialists identified the threats related to the species. Pig, climate change and fire were ranked as the most severe hazards to C. oblonga. A qualitative assessment proposed 22 predictions that described all the threats. Levels of heavy metals in fat, muscle and liver, were analysed and revealed high concentration of Cu (liver = 33.1 mg/kg; muscle = 2.99 mg/kg), Pb (muscle = 0.35 mg/kg) and Zn (liver = 51.3 mg/kg; muscle 171 mk/kg and fat = 9.6 mg/kg) according to the WHO/FAO and Gel guidelines (maximum level Cu = 0.4 mg/kg, Pb = 0.3 mg/kg and Zn = 5 mg/kg). Mercury analysis reported high Hg concentration in keratin tissues in four individuals (421.3 ng/g; 828.2 ng/g; 1656.5 ng/g and 2409.9 ng/g) (WHO/FAO Hg maximum level for safe consumption = 500 ng/g). The threats and knowledge gaps identified on this study have the potential to guide future management actions for the C. oblonga populations in the Finniss River floodplain.

Date of Award	Dec 2018
Original language	English
Supervisor	Carla C. Eisemberg (Supervisor), Keith Christian (Supervisor) & Erica Garcia (Supervisor)