The Times Australia
The Times World News

.

Breakthrough allows scientists to determine the age of endangered native fish using DNA

  • Written by Benjamin Mayne, Molecular biologist and bioinformatician, CSIRO

Identifying the age of animals is fundamental to wildlife management. It helps scientists know if a species is at risk of extinction and the rate at which it reproduces, as well as determining what level of fishing is sustainable.

Determining the age of fish has been difficult in the past — primarily involving extracting the inner ear bone, also known as the “otolith”. Layers of growth in the otolith are counted like rings on a tree to reveal an individual’s age. Unless a dead specimen is available, this method requires killing a fish, making it unsuitable for use on endangered populations.

However a non-lethal DNA test developed by the CSIRO enables researchers to determine fish age for three iconic and threatened Australian freshwater species: the Australian lungfish, the Murray cod and the Mary River cod. We outline the technological breakthrough in our research[1] just published.

Our fast, accurate and cost-effective test can be adapted for other fish species. We now hope to share this method to improve the protection of wild fish populations and help promote sustainable fisheries around the world.

gloved hands cut open fish with sciessors Traditionally, age could only be determined on a dead fish. The new method is non-lethal. Shutterstock

Iconic species at risk

Human activity has led to the population declines of the three Australian fish species at the centre of our research.

The threatened Australian lungfish is found in rivers and lakes in southeast Queensland. It’s often referred to as a “living fossil” because its extraordinary evolutionary history stretches back more than 100 million years, before all land animals including dinosaurs.

Man-made barriers in rivers reduce the movement of water, which lowers lungfish breeding rates.

Older lungfish do not have hard otolith structures, which makes determining their age difficult. Bomb radiocarbon, which analyses carbon levels in organic matter, has been used to age Australian lungfish, but this method is too expensive to be widely used.

Australian lungfish In the past, determining the age of Australian lungfish has been challenging.

The threatened Murray cod[2] is Australia’s largest freshwater fish. The Mary River cod[3] is one of Australia’s most endangered fish, found in less than 30% of its former range in Queensland’s Mary River.

Habitat destruction and overfishing are major threats to Murray cod and Mary River cod populations.

Otoliths can be used to determine age for both these cod species, however this has only been done on a population-wide scale for the more prevalent Murray cod.

Read more: Australia's smallest fish among 22 at risk of extinction within two decades[4]

Mary River cod CSIRO estimated the age of Mary River cod.

Our DNA breakthrough

When cells divide to make new cells, DNA is replicated. This can lead to DNA methylation, which involves the addition or the loss of a “methyl group” molecule at places along the DNA strand.

Research has found the level of DNA methylation is a reliable predictor of age, particularly in mammals, including humans[5].

To develop our test, we first worked with zebrafish. This species is useful when studying fish biology because it has a short lifespan and high reproductive rates. We took zebrafish whose ages were known, then removed a tiny clip of their fin. We then examined DNA methylation levels in the fin sample to identify the fish’s age.

Following this successful step, we transferred the method to Australian lungfish, Murray cod and Mary River cod. Again, we used fish of known ages, as well as bomb radiocarbon dating of scales and ages determined from otoliths.

We found despite the zebrafish and the study fish species being separated by millions of years of evolution, our method worked in all four species. This suggests the test can be used to predict age in many other fish species.

Read more: Good news from the River Murray: these 2 fish species have bounced back from the Millennium Drought in record numbers[6]

DNA strand The test uses co-called DNA methylation to estimate age. Shutterstock

A conservation management boom?

In the same way human population demographers use census data to understand and model human populations, we now have the tools to do this with animals.

We are looking to expand this DNA-based method to determine the age of the endangered eastern freshwater cod and trout cod. We will also continue to test the method across other species including reptiles and crustaceans.

This work is part of CSIRO’s ongoing efforts to use DNA to measure and monitor the environment. This includes estimating the lifespan of vertebrate species such as long-lived fish and surveying biodiversity in seawater using DNA extracted from the environment.

We envisage that in the not too distant future, these methods may be used by other researchers to better understand and manage wild animal populations.

Read more: A new study shows an animal's lifespan is written in the DNA. For humans, it's 38 years[7]

Read more https://theconversation.com/breakthrough-allows-scientists-to-determine-the-age-of-endangered-native-fish-using-dna-162084

Times Magazine

Building a Strong Online Presence with Katoomba Web Design

Katoomba web design is more than just creating a website that looks good—it’s about building an online presence that reflects your brand, engages your audience, and drives results. For local businesses in the Blue Mountains, a well-designed website a...

September Sunset Polo

International Polo Tour To Bridge Historic Sport, Life-Changing Philanthropy, and Breath-Taking Beauty On Saturday, September 6th, history will be made as the International Polo Tour (IPT), a sports leader headquartered here in South Florida...

5 Ways Microsoft Fabric Simplifies Your Data Analytics Workflow

In today's data-driven world, businesses are constantly seeking ways to streamline their data analytics processes. The sheer volume and complexity of data can be overwhelming, often leading to bottlenecks and inefficiencies. Enter the innovative da...

7 Questions to Ask Before You Sign IT Support Companies in Sydney

Choosing an IT partner can feel like buying an insurance policy you hope you never need. The right choice keeps your team productive, your data safe, and your budget predictable. The wrong choice shows up as slow tickets, surprise bills, and risky sh...

Choosing the Right Legal Aid Lawyer in Sutherland Shire: Key Considerations

Legal aid services play an essential role in ensuring access to justice for all. For people in the Sutherland Shire who may not have the financial means to pay for private legal assistance, legal aid ensures that everyone has access to representa...

Watercolor vs. Oil vs. Digital: Which Medium Fits Your Pet's Personality?

When it comes to immortalizing your pet’s unique personality in art, choosing the right medium is essential. Each artistic medium, whether watercolor, oil, or digital, has distinct qualities that can bring out the spirit of your furry friend in dif...

The Times Features

How much money do you need to be happy? Here’s what the research says

Over the next decade, Elon Musk could become the world’s first trillionaire[1]. The Tesla board recently proposed a US$1 trillion (A$1.5 trillion) compensation plan, if Musk ca...

NSW has a new fashion sector strategy – but a sustainable industry needs a federally legislated response

The New South Wales government recently announced the launch of the NSW Fashion Sector Strategy, 2025–28[1]. The strategy, developed in partnership with the Australian Fashion ...

From Garden to Gift: Why Roses Make the Perfect Present

Think back to the last time you gave or received flowers. Chances are, roses were part of the bunch, or maybe they were the whole bunch.   Roses tend to leave an impression. Even ...

Do I have insomnia? 5 reasons why you might not

Even a single night of sleep trouble can feel distressing and lonely. You toss and turn, stare at the ceiling, and wonder how you’ll cope tomorrow. No wonder many people star...

Wedding Photography Trends You Need to Know (Before You Regret Your Album)

Your wedding album should be a timeless keepsake, not something you cringe at years later. Trends may come and go, but choosing the right wedding photography approach ensures your ...

Can you say no to your doctor using an AI scribe?

Doctors’ offices were once private. But increasingly, artificial intelligence (AI) scribes (also known as digital scribes) are listening in. These tools can record and trans...