TRaCK: Tropical Rivers and Coastal Knowledge

Science and knowledge that governments, communities, industries for sustainable use of Australia's tropical rivers and estuaries

Estuary fish grow with the flow

Estuary fish grow with the flow


The number and size of barramundi and king threadfin caught in Australia’s tropical estuaries have been found to correlate directly with the size of river flows pouring into the sea.

Barra and king threadfin are the two most caught fish species in the north’s inshore fisheries.

“Many people think that, in the north, river water flowing into the sea is wasted”, says Ian Halliday from Queensland Primary Industries and Fisheries.

“But this river water is what makes an estuary an estuary—that connection between freshwater and saltwater that our commercial fisheries depend on.”

Halliday’s research is part of the Tropical Rivers and Coastal Knowledge (TRaCK) research hub. He looked specifically at the Mitchell and Flinders Rivers in Queensland and the Daly and Roper Rivers in the Northern Territory.
Comparing flow data with fish catch data logged by commercial fisheries over the last 20 years, he found a distinct correlation—the bigger the flow, the bigger the catch.

“It’s surprising how consistent the results are. Whatever estuary you look at, the higher the flow rates the higher the catch. The timing of the flow, of course, also has an impact.”

It’s not just the catch size that gets bigger with bigger flows.

“In years of higher river flow, breeding success is higher and growth rates go up. Flow affects the number of larvae and juveniles–the ‘young of the year’—but also their growth rate.”

While other TRaCK projects are working out what exactly causes the fish to grow bigger, Halliday suspects that river flow “gives the estuary a huge nutrient shot. There’s only one way to grow faster—eat more. So there’s got to be more food available to the fish.”
Halliday will present his findings at a special feature session entitled ‘The potential of the north?’ on Monday 21 September at 11.00 am, at the 12th International Riversymposium at the Brisbane Convention Centre.

TRaCK was established in 2007 as a research hub under the Commonwealth Environment Research Facilities Program to provide the science and knowledge that governments, communities and industries need for the sustainable use and management of Australia’s tropical rivers and estuaries.

TRaCK receives major funding for its research through the Australian Government’s Commonwealth Environment Research Facilities initiative; the Australian Government’s Raising National Water Standards Program; Land & Water Australia; the Fisheries Research Development Corporation and the Queensland Government’s Smart State Innovation Fund.

For interview:
Ian Halliday, Queensland Department of Employment, Economic Development and Innovation, phone 07 38179530 and mobile 0423 848 710
Riversymposium program:

For more information about TRaCK:
Ruth O’Connor, 07 3735 5094,

For media assistance:
Mary O’Callaghan, 07 3846 7111 and 0419 678 179