Scalloped hammerhead sharks have became the first species of shark to be protected by the U.S. Endangered Species Act, one of the world’s strongest wildlife conservation laws. The final rule to list four of the existing six distinct population segments of scalloped hammerhead sharks as threatened (Indo-West Pacific DPS and Central/SW Atlantic DPS) or endangered (Eastern Atlantic DPS and Eastern Pacific DPS) was published [pdf] on July 3 by the National Marine Fisheries Service. The move comes in response to a 2011 petition [pdf] from WildEarth Guardians and Friends of Animals. Weeks ago, a similar petition to list great hammerhead sharks was denied.

Including the newly described Carolina hammerhead, a cryptic species difficult to distinguish from scalloped hammerheads, there are nine recognized species in the family Sphyrnidae (which includes all hammerhead species and the closely related winghead and bonnethead sharks). Of these, the scalloped is the second largest, and can reach more than 13 feet in length. Like the better-known great hammerhead, scalloped hammerheads are found worldwide in temperate and tropical waters.

Scalloped hammerhead sharks (Sphyrna lewini) already had been considered endangered by a team of experts at the International Union for the Conservation of Nature, but its Red List statuses are scientific evaluations and not legally binding. Scientists have observed severe scalloped hammerhead shark population declines in many parts of the animals’ global range. In coastal areas of the Mediterranean Sea, hammerhead sharks in general were once abundant but haven’t been seen since 1963 [pdf]. Off of South Africa, populations have declined more than 99 percent since the 1950s [pdf]. And off the coast of the northeastern U.S., a well-known 2003 paper [pdf] on shark population declines in the previous 15 years noted that “the trend in abundance is most striking for hammerhead sharks.”

Scalloped hammerheads are among the most threatened highly migratory sharks, says Sonja Fordham, president of the environmental organization Shark Advocates International. “They travel in schools across jurisdictional boundaries, are prized for their fins, are often targeted as juveniles for their meat, and are especially unlikely to survive the stress of capture, even when carefully released.” A report [pdf] showing that the closely related great hammerhead shark has an extremely pronounced stress response to being caught by fishing gear was published earlier this year. "Due to physiological constraints, hammerheads in general are a relatively fragile shark,” says Robert Hueter, director of the Center for Shark Research at Mote Marine Laboratory in Sarasota, Fla. “So it's not surprising that the scalloped hammerhead has become endangered or threatened throughout most of its range. The question is, are the other species of hammerheads not far behind?”

Along with the great hammerhead, smooth hammerhead, and several unrelated species of sharks, scalloped hammerheads were listed on Appendix II of the Convention on International Trade in Endangered Species in 2013. An Appendix II listing is different from the Endangered Species Act, as it allows international commercial trade of these species if governments certify that the catch was sustainable. The newly listed scalloped hammerhead populations occur primarily in other countries’ waters, so the ruling has little effect on U.S. fishermen, and it is unlikely to result in U.S.-led recovery plans. More concrete action, particularly outside the U.S., is urgently needed, Fordham says. U.S. citizens concerned about the populations of hammerheads not listed as Endangered can participate in the U.S. fisheries management process by submitting public comments in support of hammerhead conservation here and encouraging cooperation with the developing world. The new ESA listing comes into effect in 60 days.