ADVERTISEMENT

5 Shark Species May Gain Protection Boost from New Findings

Two new studies make clear the global threat to sharks as well as some of the challenges conservationists face, just in time for an international meeting this week that could decide the fate of several of the iconic species
oceanic whitetip shark



Pew Charitable Trusts/Jim Abernethy

As 177 nations gather in Bangkok this week to deliberate trade restrictions on potentially endangered animals, new research reveals how important these deliberations are to the long-term survival of five species of sharks.

A study published March 1 in Marine Policy reported new, higher estimates for the numbers of sharks killed yearly: approximately 100 million sharks. Meanwhile another study published February 20 in PLoS ONE, describing the migratory patterns of the highly threatened oceanic whitetip shark, reveals why international cooperation may be the last option available to preventing this shark's extinction.

Among the 71 proposals being considered by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in Bangkok March 3–14 are four involving marine species. The proposals would move the oceanic whitetip shark, the porbeagle shark, all three species of hammerheads and all species of manta rays to an Appendix II listing, which requires anyone wishing to trade them to first procure a permit. The whitetip, porbeagle and scalloped hammerhead all had proposals considered at the last CITES meeting in 2010 but each narrowly missed the two thirds majority needed for adoption.

But shark researchers and conservation specialists hope that the new research showing just how threatened these sharks are might be enough this year for these sharks to join the only three other sharks listed on Appendix II: the whale shark, the basking shark and the great white.

“CITES is going to be a dialogue between nations that want to protect their sharks and the financial interests that want to see maximum yield and maximum sustainable yield,” says Rick MacPherson, the conservation programs director at the Coral Reef Alliance. Those nations wanting to protect sharks include an unusually high 37 countries this year. “However, the number for maximum sustainable yields are probably overestimated,” he adds.

That unsustainable level of shark fishing is exactly what the new Marine Policy paper shows. Annual shark mortality was previously estimated at 73 million, but this study added reported catch at the U.N. Food and Agriculture Organization and estimates of unreported landings and finned sharks for an estimated range of 63 million to 273 million sharks killed each year.

Barriers to protection
Sharks face a triple threat: “They are really migratory, have a really low reproductive capacity and are subjected to heavy fishing driven by a demand for international trade,” says Elizabeth Wilson, the manager of the Global Shark Conservation Campaign at the Pew Charitable Trusts, who partly funded both new studies. On top of that, few regulations and “fragmented governance”—the patchwork policies across all the countries’ waters where sharks roam—impede meaningful shark protection strategies.

“Just the fact that they migrate between political jurisdictions complicates things,” says David Shiffman, a graduate student in ecosystem science and policy at the University of Miami. “Even if one or two countries are responsible with fisheries management, if the animal doesn’t spend all its time there, then it can still be severely overfished.” In the oceanic whitetip study, Demian Chapman, of the School of Marine and Atmospheric Sciences at Stony Brook University, S.U.N.Y. and colleagues attached pop-up satellite tags to 11 oceanic whitetips off Cat Island in the Bahamas in May 2011. All but one tag reported data for up to 245 days and revealed that the sharks spent about 68 percent of their time in the Bahamas’s Exclusive Economic Zone, where long-lining and commercial trade of sharks is outlawed. The rest of that time they roamed more than 16,000 square kilometers of ocean, traveling nearly 2,000 kilometers from the safe Bahamian waters.

These findings mean two things: shark sanctuaries work (all the tagged sharks eventually returned to the Bahamas)—but that they are insufficient to protect open-water sharks. “Once you get into the open ocean, there are relatively few and sometimes no rules governing what you can and can’t take out of the water,” Shiffman says. One in six shark and ray species are classified as “threatened” by the International Union for Conservation of Nature, but one in three species of open-ocean sharks are threatened.

Then there are sharks’ life histories. These predators may be fishes, but biologically they resemble mammals more than other fishes. “Sharks management is such a conundrum for fisheries management organizations because they’re so used to fish, and sharks don’t lend themselves to traditional fisheries management policies,” MacPherson says. Unlike most fishes, sharks are slow to sexually mature, physically mate instead of spawning, have long gestation periods and produce few litters of pups. Consider the oceanic whitetip and the swordfish: Oceanic whitetips (pdf) take four to seven years to reach maturity, gestate for nine to twelve months and have litters of five to six pups every two years. Swordfish reach maturity in two to three years and produce up to 1.5 million eggs when they spawn multiple times a year, with gestations lasting about 2.5 days.

But like whales, swordfish and tuna, sharks have become big industry tickets, especially because the demand for fins began rising in the 1970s. Sharks have gone from being accidental bycatch to targets for their fins, meat, cartilage and liver oil—but regulations have not kept pace with fishing, MacPherson says. The large fins of oceanic whitetips fetch about $90 per kilogram; hammerhead fins, also large for their size, bring in $110 to $220 per kilogram. Like other pelagic fishes (those that live in the open sea or in surface waters), many sharks travel far and wide. Just a couple of sharks can pay for a day’s worth of fishing. Like whales, however, sharks cannot recover quickly from overfishing. (Fishes that can recover relatively quickly are those that grow quickly and reproduce by spawning, such as mahi-mahi, Shiffman says.) Taken together, sharks are “the fishes that are most likely to go extinct within the next few decades,” Shiffman says.

What a CITES listing would mean
A listing on CITES Appendix II might help stanch the rapid population declines of oceanic whitetips, scalloped hammerheads and porbeagles—all three have declined 90 to 99 percent since the 1950s. “For sharks and rays, it would make a world of difference,” Pew’s Wilson says. “The Appendix II listing would require countries to ensure that their exports were legal and sustainable,” she says. Fishermen might catch these sharks in open international waters but they cannot sell them without a permit. Trade without permits can lead to heavy penalties, or even sanctions on a country.

Several regional fisheries management organizations already have protections in place for the oceanic whitetip, but they are difficult to enforce. “The truth is, these regional fisheries management organizations don’t have the teeth and don’t monitor trade like CITES,” says Stony Brook’s Chapman, senior author of the PLoS oceanic whitetip study. “Countries like the U.S., Australia and New Zealand invest a lot of money in monitoring catch, doing stock assessment and enforcing regulations. Many developing countries can’t do that, but they do have customs and police. They do have the ability to say you can’t export that or you can only export that if it’s sustainable.”

The Marine Policy paper makes plain that current shark fishing levels are not sustainable. Annual shark exploitation rates range from 6.4 to 7.9 percent, the paper reported, but shark rebound rates average 4.9 percent a year. A CITES listing would mean permits could not be issued unless fishermen could show they had changed their practices to fish the sharks more sustainably. “That should help the population of a heavily exploited species to recover,” Shiffman says. And recovery means preservation of some of the ocean’s most important species.

“Hammerheads and manta rays in particular are very iconic animals,” Shiffman says. “They’re culturally significant and very important in terms of ecotourism.” Shark-related tourism added $800 million to the Bahamian economy alone over the past 20 years, according to Pew. The predators also are important to the health of entire marine ecosystems. “Oceanic sharks do a pretty good job of maintaining strong tuna stocks by culling the small and genetically weaker ones, similar to the role of the lion in the Serengeti,” MacPherson says.

The bottom line, as was true with whales and still is with bluefin tuna and other threatened fishes, is that ensuring shark species’ survival also ensures the survival of multiple fisheries. “Pro-shark protection or pro-whale protection is not anti-fishing,” MacPherson says. “If we want fishing for all the benefits it derives, whether it’s sustenance or it’s economic, if we want that for the future, we have to be willing to change our practices.”

Rights & Permissions
Share this Article:

Comments

You must sign in or register as a ScientificAmerican.com member to submit a comment.
Scientific American Back To School

Back to School Sale!

12 Digital Issues + 4 Years of Archive Access just $19.99

Order Now >

X

Email this Article



This function is currently unavailable

X