The pelagic thresher shark is one of three thresher sharks, all three known for their extremely long tails. Adult pelagic threshers’ tails are longer than the rest of the body. Scientists believe that they are highly migratory, but there have not been sufficient tagging studies to confirm that suspicion. Little is known about the ecology of pelagic thresher sharks, as they are difficult to study in their natural habitat (the open ocean).
The Pelagic thresher shark’s long tail, which can reach lengths of several meters, is used for hunting. Much like a swordfish’s or blue marlin’s bill, the tail is whipped side to side to stun or kill prey, making it particularly easy to capture. This behavior has only been observed a few times and filmed even fewer. Sport fishers, however, often catch this species by the tail. When an individual whips a fisher’s bait with its tail, it becomes hooked and is retrieved in reverse. Because pelagic thresher sharks need to swim forward to pass oxygenated water over their gills, they often die after being captured, even if they are released quickly. The pelagic thresher shark’s mouth is relatively small, and they eat small pelagic fishes and squids.
Pelagic thresher sharks mate via internal fertilization and give live birth to only two very large pups. Though they give live birth, Pelagic Threshers do not connect to their young through a placenta. Instead, during the gestation period, the mother provides her young with unfertilized eggs that they actively eat for nourishment. Unlike the closely related common thresher shark, the pelagic thresher shark is unable to control its body temperature and is truly cold blooded (like almost all fishes).
As a result of the pelagic thresher shark’s life history characteristics (very low reproductive rate, slow growth, etc.) and its capture by commercial shark fisheries and fisheries targeting other species, this shark is considered to be vulnerable to extinction. Populations around the world are declining, and scientists believe that unless negative trends are addressed soon, this species (and the other thresher sharks) may be in trouble. It is fished throughout its range and is afforded very little legal protection wherever it lives.
Oceana joined forces with Sailors for the Sea, an ocean conservation organization dedicated to educating and engaging the world’s boating community. Sailors for the Sea developed the KELP (Kids Environmental Lesson Plans) program to create the next generation of ocean stewards. Click here or below to download hands-on marine science activities for kids.