A DNA test developed by CSIRO, Australia’s national science agency, canimprove management of wild fish populations for conservation or harvest bydetermining the ages of fishes.

Postdoctoral Fellow with CSIRO’s Environomics Future Science Platform Dr BenMayne said the new method is a non-lethal alternative to counting growth ringsin their otoliths, or ear bones of fish, to reveal their age.

“We developed a fast, cost-effective DNA test for use with three threatenedAustralian freshwater species, the Australian lungfish, the Murray cod and theMary River cod, which can also be adapted for other fish species,” Dr Maynesaid.

“Knowing the ages of fish in a population is vital for their management, suchas setting sustainable harvests or determining whether a species is at risk ofextinction as well as understanding growth and reproduction of a species.

“We’re now hoping to share this test with fisheries managers to supportconservation projects and sustainable fisheries worldwide.”

Until now, most animals, including fish, didn’t have a practical and non-lethal method to determine age.

Senior Research Scientist at Seqwater Dr David T. Roberts has been conductingresearch on lungfish for over a decade.

“The search for a method to age Australian lungfish has been costly andtechnologically challenging,” Dr Roberts said.

“This breakthrough DNA-based ageing method will advance our understanding oflungfish population dynamics, providing a low cost, accurate and simple methodthat will improve conservation efforts long into the future.”

Tom Espinoza of the Queensland Department of Regional Development,Manufacturing and Water has spent 15 years working on water planning thatbalances the needs of multiple stakeholders and key aquatic species inQueensland.

“Australian lungfish, Murray cod and Mary River cod are iconic species inAustralia due to their economic, scientific and cultural value,” Mr Espinozasaid.

“Non-lethal ageing provides an important platform from which to develop thistechnique across more species and improve management of the fisheries andnatural resources that support them.”

To develop their DNA test, Dr Mayne’s team first worked with zebrafish, whichhave long been used to study fish biology, before calibrating their techniquefor threatened species using fish of known ages, bomb radiocarbon dating ofscales, and ages determined from otoliths.

The result is a rapid and cost-effective method to determine the age of afish, which is based on methylation of DNA at places in the genome known asCpG sites.

Despite the zebrafish and the Australian lungfish being separated by more than100 million years of evolution, this system is conserved and works in bothspecies.

This work is part of CSIRO’s ongoing research to develop ways to use DNA tomeasure and monitor the environment, including estimating the lifespan ofvertebrate species using DNA and surveying biodiversity in seawater usingeDNA.

“We are continuing to work with lungfish and cod in south east Queensland byageing historic genetic libraries to provide detailed demographic profiles tohelp conserve these species,” Dr Mayne said.

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