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.”