Blue sharks are curious, migratory predators that can be found throughout the global ocean ranging from the tropics to cold temperate waters. Most of their lifespan is spent far away from the coast and are truly a pelagic species. They are called blue shark because of the blue color of their skin that is distinctive even among shark species.
The blue shark has one of the largest geographic distributions among the sharks and are one of the most common pelagic sharks in the world. Although cases of individual attacks on humans have been recorded, however, this is rare as it does not happen frequently. When an attack occurs, it is mainly due to curiosity than aggressiveness. Nonetheless, it is not a timid shark and should be approached with caution. Blue shark may reach up to 9ft or 10ft in size.
The blue shark is the most heavily fished sharks in the world. The IUCN Red List classifies blue shark as a Lower Risk/Near Threatened species at global level.
Taxonomy
The scientific name of the blue shark is Prionace glauca. The shark is from the family Carcharhinidae.
Morphology
The blue shark has a slender body with a large eye and a long conical snout that is longer than the width of the mouth. It has extremely long, pointed pectoral fins, which are typically as long as the distance from its snout to posterior gill slit. The blue shark’s name comes from its distinct dark blue dorsal surface. The ventral surface is a well-defined, crisp white color. The shark is notable for its long saber-like pectoral fin. The shark can reach 13 feet in length.
Feeding
Small bony fishes, such as herring and sardines, and invertebrates, for instance, squid, cuttlefish and pelagic octopi, make up a majority of the blue shark’s diet. They feed actively at night, but are known to feed throughout the 24 hours of the day. Blue sharks often aggregate to feed on school of prey.
Habitat
In temperate waters the blue shark is a wide ranging pelagic species occurring near the surface where water depths are greater than 656 ft. It prefers temperature between 10 and 20oC.
Reproduction
The blue shark is a viviparous species, nourishing the young in the uterus and giving birth to live pups. The new born pup measure up to 16 to 20 inches in length and litters usually consist of between 25 to 50 individuals. Female reach sexual maturity at a size of 7 to 11 feet in size, while the male reaches maturity at length of 6 to 9 feet around 6 years old. Once the eggs have been fertilized, there is a gestation period of between 9 and 12 months. After copulation, the females may retain and nourish the spermatozoa in the oviduct gland for months or even years while she awaits ovulation. Some female blue sharks can even produce as many as 130 pups.
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References
Animals Network Team (2020). Blue Shark. Retrieved from https://animals.net/blue-shark/
Earth Touch News (2014, October 7). Top 10: Things you should know about blue sharks. Retrieved from https://www.earthtouchnews.com/oceans/sharks/top-10-things-you-should-know-about-blue-sharks/
Fisheries and Oceans Canada (2018). Blue Shark. Prionace glauca. Retrieved from https://www.dfo-mpo.gc.ca/species-especes/profiles-profils/blueshark-requinbleu-eng.html
Florida Musuem (2020). Prionace glauca. Blue Shark. Retrieved from https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/prionace-glauca/
OCEANA (2020). Blue Shark. Prionace glauca. Retrieved from https://oceana.org/marine-life/sharks-rays/blue-shark
The Wildlife Trusts (2020). Blue Shark. Prionace glauca. Retrieved from https://www.wildlifetrusts.org/wildlife-explorer/marine/fish-sharks-skates-and-rays/blue-shark