Australian scientists have captured and tagged one of the world’s rarest species of shark in the far reaches of northern Queensland.

In a world first, researchers tagged and released two adult speartooth shark specimens, a feat expected to provide greater understanding of the secret lives of this elusive and critically endangered species of shark.

A team of CSIRO scientists led by marine researcher Dr Richard Pillans spent nine days in the tropical waters of the Wenlock River in far north Queensland before they were able to capture both male and female adult speartooths, measuring 2.3m and 2.2m long, respectively.

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“Before this trip, there’s no record of [speartooth shark] adults in Australia,” Dr Pillans told The New Daily.

Dr Pillans’ team collected DNA samples and attached two satellite tags on each of the catches, which have been programmed to collect information on water temperature and depth before detaching after 60 days and 120 days.

According to a leading shark expert, the satellite tags attached to the two adult sharks will not only provide GPS information of where they have travelled, but also allow conservationists to better target habitat areas for protection.

“The more we look into how sharks move and use their habitats, the more surprises we get,” James Cook University’s Dr Andrew Chin told The New Daily.

“We’re finding that some sharks can be very attached to particular sites and that makes looking after those locations more important than we’ve previously thought.”

Until now, researchers had only ever captured and studied the juveniles of the species – the only thing known about the adults was that the mothers gave birth to live young, which was evidenced by the discovery of fresh umbilical scars in the juveniles.

Dr Pillans has been conducting research into the movement and population status of juvenile speartooths in the Wenlock River since 2006 and has observed them to be highly sensitive to the salt levels in the water, or salinity.

“The juvenile speartooth shark don’t really tolerate fresh water all that well,” Dr Pillans said.

“During the wet season, as soon as it starts to flood and the salinity drops, all of the little sharks move out on that salinity front and move out into the bay … where there’s a mixture of fresh water and seawater, so it’s a more comfortable environment.”

Dr Pillans was also able to determine maturity of the male specimen by examining its reproductive organs, called claspers.

“Once male sharks reach maturity, the claspers basically become disproportionately long in relation to the body, and they also become calcified and hard,” he said.

“It’s the easiest way to determine whether a male shark is sexually mature.”

Besides commercial and illegal fishing activities playing a role in the species’ scarce numbers, Dr Chin also believes climate change to be another key factor.

“We did an assessment of how climate change could affect sharks and rays in the Great Barrier Reef, and the freshwater and estuarine sharks came up as the ones that are most vulnerable,” Dr Chin said.

“The [river] systems they rely on could be affected a lot by climate change in terms of prolonged droughts and heavy flooding with high salinity changes that lead to the harsh environmental conditions and damage to habitats they live in.”

Dr Pillans has to wait for the timed release of the satellite tags, where the data collected will be fed into a model to estimate adult population size.

“We still don’t know whether the population is continuing to decline or stable or increasing, and not knowing the habitats where the adults live is a critical gap in our ability to manage how the species is going,” Dr Pillans said.