Featured Research

from universities, journals, and other organizations

Sharks are in trouble, new analysis confirms

Date:
September 30, 2011
Source:
ARC Centre of Excellence in Coral Reef Studies
Summary:
Sharks are in big trouble on the Great Barrier Reef and worldwide, according to an Australian-based team who have developed a world-first way to measure rates of decline in shark populations.

A finned reef shark in the Great Barrier Reef World Heritage Area. This carcass was one of several found illegally dumped at Wreck Beach on Great Keppel Island.
Credit: Photo taken by R. Berkelmans on 17 November 2006

Sharks are in big trouble on the Great Barrier Reef and worldwide, according to an Australian-based team who have developed a world-first way to measure rates of decline in shark populations.

"There is mounting evidence of widespread, substantial, and ongoing declines in the abundance of shark populations worldwide, coincident with marked rises in global shark catches in the last half-century," say Mizue Hisano, Professor Sean Connolly and Dr William Robbins from the ARC Centre of Excellence for Coral Reef Studies and James Cook University.

"Overfishing of sharks is now recognized as a major global conservation concern, with increasing numbers of shark species added to the International Union for the Conservation of Nature's list of threatened species," they say in the latest issue of the international science journal PLos ONE.

"Evaluating population trends for sharks is complicated," explains Professor Connolly. "The simplest approach of looking at trends in fisheries catches doesn't work well for sharks. First, many countries with coral reefs don't keep reliable records of catches or fishing effort. Second, around 75 per cent of the world shark catch consists of illegal and unreported finning. Third, sharks may be caught, discarded, and not reported when fishers are targeting other species."

"An alternative is to take estimates of shark growth, birth, and mortality rates, and use these to calculate population growth rates. Estimates of growth and birth rates are easy to get, but it is very hard to get good estimates of mortality in sharks and other large animals," he says.

To deal with this problem, the team developed several alternative models, which combined birth rates and growth rates for sharks with a variety of different methods for estimating mortality. They then used state-of-the art statistical methods to combine the uncertainty associated with each of these methods and arrive at a more robust long-term population prediction for two GBR shark species -- the grey reef shark and the whitetip reef shark.

As a further check on their results, the researchers used their population projections to see how well their models could explain differences in shark abundances on fished and unfished reefs, based on how long the unfished reefs had been protected.

The team found that results obtained by all methods of assessing shark populations were in close agreement that sharks are declining rapidly due to fishing.

"Our different approaches all painted a surprisingly consistent picture of the current state of population decline, but also of the potential recovery of these species if they are adequately protected," says Mizue Hisano, the study's lead author.

For the Great Barrier Reef shark populations, the close agreement between the different methods appears to justify management actions to substantially reduce the fishing mortality of reef sharks.

"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."


Story Source:

The above story is based on materials provided by ARC Centre of Excellence in Coral Reef Studies. Note: Materials may be edited for content and length.


Journal Reference:

  1. Mizue Hisano, Sean R. Connolly, William D. Robbins. Population Growth Rates of Reef Sharks with and without Fishing on the Great Barrier Reef: Robust Estimation with Multiple Models. PLoS ONE, 2011; 6 (9): e25028 DOI: 10.1371/journal.pone.0025028

Cite This Page:

ARC Centre of Excellence in Coral Reef Studies. "Sharks are in trouble, new analysis confirms." ScienceDaily. ScienceDaily, 30 September 2011. <www.sciencedaily.com/releases/2011/09/110929103057.htm>.
ARC Centre of Excellence in Coral Reef Studies. (2011, September 30). Sharks are in trouble, new analysis confirms. ScienceDaily. Retrieved September 20, 2014 from www.sciencedaily.com/releases/2011/09/110929103057.htm
ARC Centre of Excellence in Coral Reef Studies. "Sharks are in trouble, new analysis confirms." ScienceDaily. www.sciencedaily.com/releases/2011/09/110929103057.htm (accessed September 20, 2014).

Share This



More Earth & Climate News

Saturday, September 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Wildfires in CA Burn Forest Asunder

Raw: Wildfires in CA Burn Forest Asunder

AP (Sep. 18, 2014) An out-of-control Northern California wildfire has nearly 2,800 people from their homes as it continues to grow, authorities said Thursday. Authorities said a man has been arrested on suspicion of arson for starting the fire on Saturday. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Elephant Undergoes Surgery in Tbilisi Zoo

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

AP (Sep. 18, 2014) Grand the elephant has successfully undergone surgery to remove a portion of infected tusk at Tbilisi Zoo in Georgia. British veterinary surgeons used an electric drill to extract the infected piece. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Man Floats for 31 Hours in Gulf Waters

Man Floats for 31 Hours in Gulf Waters

AP (Sep. 16, 2014) A Texas man is lucky to be alive after he and three others floated for more than a day in the Gulf of Mexico when their boat sank during a fishing trip. (Sept. 16) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins