Sharks in Australia's Great Barrier Reef in decline

September 28, 2011
This file illustration photo shows people watching a whale shark swimming in an aquarium. Sharks inhabiting Australia's Great Barrier Reef are in decline due to over fishing, researchers warned, after developing what they said was a new way to measure falling numbers.

Sharks inhabiting Australia's Great Barrier Reef are in decline due to over fishing, researchers warned, after developing what they said was a new way to measure falling numbers.

Academics from James Cook University in Queensland on Wednesday said there was mounting evidence of widespread and substantial declines in shark populations around the world, with some species now listed as threatened.

Professor Sean Connolly said assessing the numbers of sharks was difficult -- not least because many were caught accidentally while intending to catch other fish and some killed for their fins.

Using a new analytical approach, the researchers looked at the growth rates, reproductive capability and projected of two -- the grey reef shark and the whitetip reef shark.

They then used to arrive at long-term population predictions for both species.

To further check their results, they compared them with data on shark population in areas where fishing is legal, green zones in which boats are allowed but fishing banned, and pink zones in which boats are banned.

The researchers found that the results using all the various methods of assessing shark populations were in close agreement and that sharks were declining due to fishing.

"Shark declines are quite rapid," Connolly said.

"Our consensus estimates are around six percent per year decline for whitetip reef sharks and nine percent for grey reef sharks."

Given the range of uncertainty around the estimates, the decline could potentially be even greater, he added.

He said these figures were just for Australia, but in countries with fewer fishing restrictions the numbers were expected to be worse.

" in other countries with significant in our region are going to be in much worse shape even than ours are -- and ours are not in good shape," Connolly said.

The findings, published in science journal , could help researchers with the potential recovery of these species if they were adequately protected, lead author Mizue Hisano said.

"More broadly, we believe that our study demonstrates that this approach may be applied to a broad range of exploited species for which direct estimates of mortality are ambiguous or lacking, leading to improved estimates of population growth," Hisano said.

Explore further: Ongoing collapse of coral reef shark populations

Related Stories

Ongoing collapse of coral reef shark populations

December 4, 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 ...

Reef sharks threatened by overfishing

December 5, 2006

A study by Australian scientists has warned that coral reef shark populations on the Great Barrier Reef are in the midst of a catastrophic collapse.

Ocean's fiercest predators now vulnerable to extinction

February 17, 2008

The numbers of many large shark species have declined by more than half due to increased demand for shark fins and meat, recreational shark fisheries, as well as tuna and swordfish fisheries, where millions of sharks are ...

Conservation dollars and sense

June 27, 2011

Shark populations over the last 50 years have decreased dramatically. From habitat degradation to overfishing and finning, human activities have affected their populations and made certain species all but disappear.

Recommended for you

New discovery challenges long-held evolutionary theory

October 19, 2017

Monash scientists involved in one of the world's longest evolution experiments have debunked an established theory with a study that provides a 'high-resolution' view of the molecular details of adaptation.

Gene editing in the brain gets a major upgrade

October 19, 2017

Genome editing technologies have revolutionized biomedical science, providing a fast and easy way to modify genes. However, the technique allowing scientists to carryout the most precise edits, doesn't work in cells that ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.