Reef sharks in steep decline, study shows

2012-04-28 08:01

Washington - Reef sharks, which are often killed for their fins or caught in fishing nets, have declined to 10% of historic levels near populated islands in the Pacific Ocean, US scientists said on Friday.

The survey by the University of Hawaii showed that the numbers were drastically lower near populated islands in Hawaii, the Mariana Archipelago and American Samoa, compared to more pristine, remote areas in the ocean.

"We estimate that reef shark numbers have dropped substantially around populated islands, generally by more than 90% compared to those at the most untouched reefs," said Marc Nadon, lead author of the study in the journal Conservation Biology.

"In short, people and sharks don't mix," added Nadon, a scientist at the university's Joint Institute for Marine and Atmospheric Research.

The latest research was based on a method called "towed-diver surveys," in which paired scuba divers record shark sightings while being towed behind a small boat.

"Towed-diver surveys are key to our effort to quantify reef shark abundance," said Ivor Williams, head of the team responsible for the surveys.

"Unlike other underwater census methods, which are typically at an insufficient spatial scale to properly count large, mobile species, these surveys allowed our scientists to quickly record shark numbers over large areas of reef."

Researchers analysed data from over 1 600 towed-diver surveys taken from 2004-2010, in combination with information on human population growth and reef area, as well as satellite-data on sea surface temperature and ocean traits.

"Around each of the heavily populated areas we surveyed - in the main Hawaiian Islands, the Mariana Archipelago, and American Samoa - reef shark numbers were greatly depressed compared to reefs in the same regions that were simply further away from humans," Nadon said.

"We estimate that less than 10% of the baseline numbers remain in these areas."

Researchers counted five types of reef sharks for the study, including the most common types - gray and whitetip reef sharks - as well as blacktip reef sharks, Galapagos sharks and nurse sharks.

"The pattern - of very low reef shark numbers near inhabited islands - was remarkably consistent, irrespective of ocean conditions or region," said co-author Julia Baum, assistant professor at the University of Victoria, Canada.

Co-authors came from the University of California Santa Barbara; the Centre for Conservation Research in Calgary, Canada; Simon Fraser University; Scripps Institution of Oceanography and the US National Oceanic and Atmospheric Administration.

Read more on:    us  |  research  |  marine life
NEXT ON NEWS24X
SHARE:

Read News24’s Comments Policy

24.com publishes all comments posted on articles provided that they adhere to our Comments Policy. Should you wish to report a comment for editorial review, please do so by clicking the 'Report Comment' button to the right of each comment.

Comment on this story
3 comments
Add your comment
Comment 0 characters remaining

Inside News24

 
/News

Jobs in Cape Town [change area]

Property [change area]

Travel - Look, Book, Go!

Kalahari.com - shop online today

Valentine’s Day gifts – 14 Feb!

Gifts to spoil him and her. While stocks last. Shop now!

Games on Sale!

Save up to 60% on selected games. While stocks last. Shop now!

Up to 30% off All Textbooks

Save up to 30% off an extensive range of prescribed textbooks for all major universities and FET colleges. Shop Now!

Save up to 40% on outdoor accessories!

Tents, sleeping, day packs and more. While stocks last. Shop now!

30% off fragrances

Get 30% off fragrances for him and her. While stocks last. Shop now!

OLX Free Classifieds [change area]

Horoscopes
Aquarius
Aquarius

Today is a good day to connect to your inner needs and try to get things back into a more balanced rhythm. There will be emotional...read more

There are new stories on the homepage. Click here to see them.
 
English
Afrikaans
isiZulu

Hello 

Create Profile

Creating your profile will enable you to submit photos and stories to get published on News24.


Please provide a username for your profile page:

This username must be unique, cannot be edited and will be used in the URL to your profile page across the entire 24.com network.

Settings

Location Settings

News24 allows you to edit the display of certain components based on a location. If you wish to personalise the page based on your preferences, please select a location for each component and click "Submit" in order for the changes to take affect.




Facebook Sign-In

Hi News addict,

Join the News24 Community to be involved in breaking the news.

Log in with Facebook to comment and personalise news, weather and listings.