Australia 'has two distinct white shark populations'

Jun 05, 2012

(Phys.org) -- A new scientific study has identified two distinct populations of white shark at the east and west of Bass Strait in Australian waters, prompting researchers to suggest the huge fish may need regional conservation plans.

Published in the journal , the paper is authored by researchers from the ARC Centre of Excellence for Coral , The University of Queensland, CSIRO Wealth from Oceans Flagship and the Department of Agriculture, Fisheries and Forestry (DAFF Queensland).

“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,” Professor John Pandolfi, a Chief Investigator at CoeCRS and UQ, said.

“This shows that while the sharks can roam around Australia and across ocean basins, they repeatedly return to their home region to breed.”

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

Its findings are broadly consistent with satellite and acoustic tracking research led by CSIRO's Barry Bruce.

“Our tagging and tracking showed that white sharks travel thousands of kilometres,” Mr 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.

“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.”

The study builds on results by other international research teams that have identified separate genetic populations of white sharks across basins.

However, this is the first time such differences have been found at the regional scale.

White shark numbers declined in the 20th century and the species is now protected in South Africa, the United States, Australia, New Zealand, Malta, Namibia, throughout the Mediterranean Sea and globally under the Convention on International Trade in Endangered Species (CITES).

However, a lack of information on abundance, genetic diversity, reproductive behaviour and population structure has prevented accurate assessment of the effectiveness of white shark conservation programs, including an understanding of their population trends.

“The finding may indicate that individual populations of are more susceptible than previously thought to threats including fishing or changes in the local marine environment,” Dr Jennifer Ovenden from DAFF said.

“The key will be to develop regional rather than national management strategies, and to ensure populations are monitored in both regions.”

Explore further: 'Killer sperm' prevents mating between worm species

More information: The paper “Population genetics of Australian white sharks reveals fine-scale spatial structure, transoceanic dispersal events and low effective population sizes” by Dean C. Blower, John M. Pandolfi, Barry D. Bruce, Maria del C. Gomez-Cabrera and Jennifer R. Ovenden was published in the journal Marine Ecology Progress Series. It is available at bit.ly/JSkHo7

add to favorites email to friend print save as pdf

Related Stories

Over 100 new sharks and rays classified

Sep 18, 2008

(PhysOrg.com) -- Australian scientists have completed an ambitious 18-month project to name and describe more than 100 new species of sharks and rays.

Ongoing collapse of coral reef shark populations

Dec 04, 2006

Investigators have revealed that coral reef shark populations are in the midst of rapid decline, and that "no-take zones" -- reefs where fishing is prohibited -- do protect sharks, but only when compliance with no-take regulations ...

Recommended for you

Chinese mosquitos on the Baltic Sea

1 hour ago

The analysis of the roughly 3,000 pieces is still in its infant stage. But it is already evident that the results will be of major significance. "Amazingly often, we are finding–in addition to Asian forms–the ...

Baby zebra is latest success in research partnership

2 hours ago

The recent birth of a female Grevy's zebra foal at the Saint Louis Zoo marks another milestone in a long-running Washington University in St. Louis research partnership that is making significant contributions ...

'Killer sperm' prevents mating between worm species

20 hours ago

The classic definition of a biological species is the ability to breed within its group, and the inability to breed outside it. For instance, breeding a horse and a donkey may result in a live mule offspring, ...

Rare Sri Lankan leopards born in French zoo

23 hours ago

Two rare Sri Lankan leopard cubs have been born in a zoo in northern France, a boost for a sub-species that numbers only about 700 in the wild, the head of the facility said Tuesday.

User comments : 0