Common name: estuary stingray
Scientific name: Hemitrygon fluviorum
Family: Dasyatidae (stingrays)
Conservation status: The estuary stingray is listed as Near Threatened in Queensland (Nature Conservation Act 1992), and is considered a high priority for conservation under the department's Back on Track species prioritisation framework.
Description: The estuary stingray is plain brown or tan in colour and has a row of small thorns running down the middle of the back and along the tail. It grows to about 120 cm across the body and has a long whip-like tail.
Habitat and distribution
This species is found in mangrove-fringed rivers and estuaries, and offshore to at least 28 m depth, but more commonly in shallow inshore waters. As well as occurring in marine and estuarine waters, it is known to move up rivers to beyond the tidal limit.
Estuary stingrays were once common in south-east Queensland. However, the rapid urban growth along the Gold Coast, Moreton Bay and Sunshine Coast coastline has placed enormous pressure on their habitat. Historically, the estuary stingray was present on the east coast from Port Jackson, New South Wales, to the tropics, but it has not been reported along the central New South Wales coast since the 1880s. The estuary stingray is currently found from Forster in New South Wales to Proserpine in Queensland.
Life history and behaviour
The species is reported to be a major predator of shellfish, including farmed oysters. Individuals move over mudflats with the incoming tide to feed, and in Moreton Bay, southern Queensland they have been found to feed on soldier crabs.
Even the answers to basic questions about estuary stingray, such as their age at maturity and lifespan, are unknown.
The estuary stingray was once common, but there has been a considerable contraction of its range and a decline in abundance. Numerous human induced threats have been contributing factors in this decline. Development and construction of industries, marinas and urban settlements in coastal areas has been accompanied by substantial losses of estuarine wetlands. The species appears particularly vulnerable to such human activities due to its reliance on shallow tidal and mangrove habitats, particularly within estuaries and rivers.
Bycatch in commercial fisheries, persecution by shellfish farmers and destruction of incidental catches by recreational fishers and during some commercial fishing activities have also contributed to this decline. It has been shown that a high proportion of rays in some areas of Moreton Bay bear hook wounds and fishing-related injuries.
- There is a lack of information about the abundance of this species, further surveys to determine abundance and distribution are required.
- Educate commercial fishers, aquaculturists and recreational fishers to halt the destruction of incidental captures of the species.
- Protect important mangrove communities and estuaries, from destruction and degradation, through appropriate marine zoning.
- Minimise the amount of pollution and sediment output into coastal waters through appropriate catchment management.
What can be done to help this species?
- If you catch a stingray, remove the hook before release. If your hook has a barb, use bolt-cutters to remove the barb, and then pliers or a hook-removing device to remove the hook.
- Avoid using stainless steel hooks. If these are left in the animal after capture they can last for years as they do not rust. They continually wear leaving the wound raw and open for infection that can eventually kill.
- Release the animal back into the water as soon as possible. Do not kill or injure stingrays if you catch them.
Curtis, LK, Dennis, AJ, McDonald, KR, Kyne, PM and Debus, SJS (eds) 2012. Queensland’s Threatened Animals, CSIRO Publishing, Victoria.
Kyne, P.M., Pollard, D.A. & Bennett, M.B. 2016. Hemitrygon fluviorum. The IUCN Red List of Threatened Species 2016.