One year after The Bahamas created a permanent shark sanctuary in its waters, an unprecedented tagging effort reveals just how important the protected area is to the globally threatened oceanic whitetip shark. According to a new study, this species, once widely thought to roam only the open ocean, actually spends a lot of its time returning to the same locations.
A paper published today in the online journal PLOS ONE found that although oceanic whitetip sharks tagged in The Bahamas travel far and varied distances, they spend a lot of their time in the exclusive economic zone of The Bahamas, which was declared a shark sanctuary in July 2011. Moreover, individual sharks often return to the area after migrating elsewhere. According to the authors, the data collected for this study suggest that these sharks have a home base. This information could provide the first scientific evidence of this kind of behavior for the species, which is thought to be especially wide-ranging. Separate studies show that other, less wide-ranging shark species such as the lemon shark also return to the same area.
“Although they are a highly migratory species, our research shows that whitetips characteristically return to the same areas after trips to the open ocean,” said Demian Chapman, a co-author of the research and the assistant science director of the Institute for Ocean Conservation Science at Stony Brook University in New York. “These findings can offer crucial information for providing greater protections for this threatened species in The Bahamas and in other places where whitetips gather around the world.”
The oceanic whitetip shark is an open-ocean species with a distinctive white tip on its dorsal fin. In May 2011, scientists tagged 12 of the sharks and successfully tracked 11 of them in The Bahamas, an unprecedented number for researching this species. Previously, only one other oceanic whitetip had been tagged. The sharks were fitted with a pop-up satellite tag that collects and stores data on temperature, depth, and light, used to estimate position. The tags were programmed to pop off the sharks after a certain period, varying from roughly one month to more than eight months.
Sharks are important to study because they play a crucial role in maintaining healthy coastal ecosystems and because other commercially important species depend on sharks to prey on and remove the weak and sick, allowing healthier fish to thrive in their place. Sharks are economically significant as well: Over the past 20 years, shark-related tourism has contributed more than US$800 million dollars to the Bahamian economy. In recognition of this, the Bahamian government banned all commercial shark fishing in the approximately 630,000 square kilometers (240,000 square miles) of the country's waters in July 2011.
Unfortunately there are few limits on the number of sharks that can be killed beyond the sanctuary, and concerted action is needed around the world to reverse the decline of global shark populations.Liz Karan, The Pew Charitable Trusts
Seven other countries and territories around the world—Palau, Honduras, the Marshall Islands, Tokelau, the Maldives, and most recently the Cook Islands and French Polynesia—also have taken the bold step of permanently protecting sharks in their waters. These sanctuaries cover more than 11.4 million square kilometers (4.4 million square miles) of ocean. Sanctuaries are an important step in protecting shark species such as the oceanic whitetip, which is listed on the International Union for Conservation of Nature's Red List of Threatened Species as Critically Endangered in the northwest and central Atlantic Ocean and Vulnerable globally.
“The iconic oceanic whitetip, though vulnerable around the world, has a safe haven in the Bahamas shark sanctuary,” said Liz Karan, manager of global shark conservation for The Pew Charitable Trusts. “Unfortunately there are few limits on the number of sharks that can be killed beyond the sanctuary, and concerted action is needed around the world to reverse the decline of global shark populations.”
Discussions are underway about improving protections beyond sanctuaries for oceanic whitetip sharks. In March, 177 governments from around the world will meet during the Conference of the Parties for the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) to talk about international trade protections for whitetip and porbeagle sharks, three species of hammerhead sharks, and two types of manta rays. For nearly 40 years, this agreement on global trade has shielded thousands of plants and animals from overexploitation, and the treaty is widely considered one of the best-enforced international conservation agreements.