Blue sharks are curious, open-ocean predators that live throughout the global ocean, from the tropics to cold temperate waters. They spend most of their lives far from the coast and are truly a pelagic species. The common name comes from the blue color of the skin, unique among the sharks.
Though they may reach lengths of up to nine or ten feet (3 m), blue sharks specialize in relatively small prey, including small pelagic fishes and small squids, and they undertake regular feeding dives to deeper pelagic waters, likely to hunt.
Blue sharks are known to be highly migratory, with individuals making several trips across entire ocean basins throughout their lifetimes. Experts believe that blue sharks use their large pectoral fins (horizontal fins growing out from either side of the body) to ride long currents, conserving energy as they migrate. Blue sharks go on these long migrations to reach areas of dense food resources and to find potential mates. For most of the year, males and females of this species live in different places. Only during the mating season do they come together, briefly, and reproduce via internal fertilization. Males may aggressively bite females during mating, so females have thick protective skin, to prevent injury when they come in contact with males. Females give live birth, and litters are known to rarely reach sizes of more than 100 pups.
In some places, the blue shark is an important species to marine tourism as divers, photographers, etc. enjoy encountering it. In rare instances, individuals have bitten people, but this happens only very infrequently. The blue shark has one of the largest geographic distributions among the sharks and was historically one of the most (if not the most) common pelagic sharks in the world. Its wide distribution and dense population structure makes the blue shark a target of fisheries in some areas and a common accidentally caught species in gillnet and longline fisheries targeting other species. Furthermore, its fins are considered highly valuable, and blue sharks may be the target of illegal ‘shark finning’ operations, where the fins are cut off and kept, while the rest of the shark is wasted. Though experts believe it is only ‘near threatened’ with extinction (as a result of its wide range), the blue shark’s numbers have decreased by as much as 80% in some areas. Therefore, it is important to continue to monitor the targeted and incidental catch of this species and to update its population trends as new information becomes available.
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.