Great white sharks off the coast of Australia consist of two genetically distinct populations, according to a new study in the journal Marine Ecology Progress Series.

The finding adds to the growing body of evidence that substantial genetic differences may not always be detectable visually. For example, it was determined that the desert tortoise is at least two different species.

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In this case, scientists discovered that great white sharks at different points of Bass Strait represent unique populations. The scientists haven't yet used the "s" word- species, but other coverage of the research has done so.

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The authors of the paper do call for a reexamination of conservation plans.

“The genetic makeup of white sharks west of Bass Strait was different from those on the eastern seaboard of Australia – despite the lack of any physical barrier between these regions,” John Pandolfi, a Chief Investigator at the ARC Centre of Excellence for Coral Reef Studies and the University of Queensland, was quoted as saying in a press release. “This shows that while the sharks can roam around Australia and across ocean basins, they repeatedly return to their home region to breed.”

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For the study, Pandolfi and his team examined tissue samples from 97 sharks collected around Australia since 1989. The sharks were caught in beach safety programs, as fishery bycatch and during CSIRO field research.

Satellite and acoustic tracking research, led by CSIRO's Barry Bruce, supported the tissue analysis findings.

“Our tagging and tracking showed that white sharks travel thousands of kilometres,” Bruce said. “But sharks tagged and tracked off eastern Australia did not go west of Bass Strait, and sharks tagged off Western and South Australia rarely went east. When they did – they often returned, so we started to wonder whether there was more than one breeding population."

He continued, “Now we know that while white sharks across Australia can mix, the intriguing thing is that they seem to return to either east or western regions to breed.”

Research teams working in other parts of the world have identified separate genetic populations of white sharks across ocean basins, but this is the first time such differences have been found at the regional scale.

As for nearly all sharks, great whites are threatened, so information like this can really help conservation efforts, so long as any legislation protecting the big fish is enforced.

“The finding may indicate that individual populations of white sharks are more susceptible than previously thought to threats including fishing or changes in the local marine environment,” said Jennifer Ovenden, who is with Queensland's Department of Agriculture, Fisheries and Forestry. “The key will be to develop regional rather than national management strategies, and to ensure populations are monitored in both regions.”