North Australian FISH FINDER forums

The popular northern queenfish grows slower than thought, sexually maturing at about five years of age and 72cm in length, a CSIRO study has found.

The year-long study of the life-cycle of the giant queenfish will be used to help manage the species.

The study - co-funded by the Australian Department of Environment and Heritage (DEH) through the National Oceans Office (NOO) - examined the age, growth and reproduction of queenfish which are mainly found in tropical estuarine and coastal habitats.

More than 300 queenfish specimens were collected from the Gulf of Carpentaria near Weipa with the help of charter, recreational and commercial fishers. Gonads were collected monthly from males and females of all sizes to determine their breeding season, and length and age at sexual maturity.

"Queenfish mature at about 72 centimetres and four to five years of age - later than expected given their close relatives often mature in less than two years," CSIRO fish biologist Dr Shane Griffiths says.

"Spawning occurs during the September-February 'wet' season, peaking in November, and females can release up to two million eggs in this period. It remains a mystery where queenfish actually reproduce, but we know some individuals spawn in offshore waters."

One surprising finding was that queenfish grow slower than their closest relatives, the trevallies.
"Male and female queenfish have similar growth rates, reaching about 30 cm after one year and 80 cm after five years, but their growth then slows abruptly," Dr Griffiths says. "The oldest fish we aged was 11 years and nine kilograms, but we believe they could live to at least 15 years."

Dave Donald, of Dave Donald Sportfishing Charters at Weipa, says the research raises concerns that queenfish may need protection using minimum size and bag limits, if queenfish catches continue to escalate in recreational and commercial fisheries either as a target or bycatch species.

"The reputation of queenfish as one of Australia's top sporting fish has also enhanced its desirability with international anglers, particularly from Japan and the United States," Mr Donald says. "Because they mature later in life than expected, they may not have the ability to recover quickly if populations decline."

National Oceans Office planning manager, Rowan Wylie, says the queenfish study is contributing an understanding of the species and ecosystems of the Gulf of Carpentaria that is crucial to the development of Australia's second regional marine plan covering the gulf and Arafura Sea.

The research also contributes to the broader understanding of the ecosystem of the northern prawn fishery - a focus of CSIRO research for more than 40 years.