Barramundi benefit from ‘gap year’ in fresh water

News release | 24-Feb-2022

More than a third of adult barramundi spend their ‘teenage’ years in fresh water, researchers have found.

And, like any gap year, this appears to assist their personal growth—barramundi that spend time in fresh water as juveniles grow faster and larger than those that spend their whole lives in salt water.

Researchers analysed otoliths—fish ear bones which grow rings every year (much like trees)—to learn where barramundi had lived at different stages of their lives.

Department of Agriculture and Fisheries (DAF) senior scientist Dr Susannah Leahy said 33% of barramundi caught in the Townsville and Burdekin marine fishery had spent at least one year in fresh water as juveniles.

“Born in salt water, these fish made their way upstream to freshwater lagoons during wet seasons,” Dr Leahy said.

“They grew significantly faster and larger than their brethren that stayed in salt water their whole lives.

“This research highlights the importance of healthy freshwater habitats and fishways enabling barramundi to travel upstream.”

Dr Leahy said 3% of the barramundi caught in estuaries had originally been stocked into local dams and weirs—a small number despite the 2019 floods.

“Tens of millions of barramundi fingerlings have been released into dams and weirs in Queensland since the 1980s,” she said.

“When impoundments spill over during floods, some of these stocked fish can move downstream and join the wild population in the estuaries and ocean.

“We detected genetic ancestry from stocked fish in the wild population, which means these fish do breed when they reach salt water. This highlights the importance of fish stocking policies that support local genetic diversity.

“Our work shows that the biggest benefit to the wild barramundi population comes from juvenile fish—wild or stocked—getting access to healthy freshwater habitats.”

Funded by DAF and the Fisheries Research and Development Corporation, this project was carried out by a team of scientists from DAF, James Cook University, and the University of Western Australia.

Dr Leahy thanked the Townsville Barramundi Restocking Group, Burdekin Fish Restocking Association, Cungulla Recreational Fishing and Social Club and participating aquaculture facilities for their assistance.

Read the final report.

Media contact: DAF Media, media@daf.qld.gov.au