13 March 2014
In September 2012, as Top End floodplains were drying out, Daly River Traditional Owner Rita Purak discovered two largetooth sawfish stranded in an isolated floodplain waterhole.
Rita knew the sawfish were uncommon because she had been helping Charles Darwin University scientist Peter Kyne with his field work, monitoring the movements of sawfish in the Northern Territory’s largest perennial river.
“After a two-hour drive across a rugged dry floodplain with the Malak Malak Indigenous Ranger Group, we found a tiny, shallow waterhole less than 50 centimetres deep,” Peter said.
“We put in a small gillnet and found nine sawfish and two barramundi, just holding on, so we collected them and returned them to the river. Two weeks later the waterhole was completely dry.”
Watch a video produced by independent film maker Jacqui Hyne, which documents the rescue.
Peter says largetooth sawfish are born at the river mouth then move upstream, often spreading out into floodplain billabongs during the wet season. Sometimes they get trapped when the floodplains dry out.
Historically, the greatest threats to the world’s largest freshwater fish have been overfishing and loss of habitat. The Daly River is a significant system for the species, yet throughout two years of sampling, less than 30 individuals have been recorded.
The relatively good condition of northern Australia’s river systems is probably one of the main reasons why populations of threatened species, including the largetooth sawfish, have been able to persist.
”Northern Australia is a global stronghold for threatened sawfishes, but we still don’t have a handle on their present status,” Peter says.
”The Malak Malak Indigenous rangers and Traditional Owners have a unique understanding of sawfish habitats in the Daly River region, and by working together we have been able to locate important floodplain areas which act as nursery areas for young sawfish.”
Peter’s research is led by the Marine Biodiversity hub of the National Environmental Research Program. His findings are also contributing to a Northern Australia hub project which is investigating the key factors that support aquatic species, and the importance of connectivity between the floodplain, river and ocean.
His team has been assisted by the Malak Malak ranger group, Traditional Owners, Northern Territory Fisheries, cattle station owners, and students and volunteers from Charles Darwin University.
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