Blue Shark Classification
Species: P. glauca
Blue Shark Description
The blue shark is a medium-sized pelagic shark. The dorsal side of the shark is indigo-blue colored with its long and sleek structures. The shark migrates for long distances and can swim rapidly.
The body of the blue shark is up to 10 ft long and its weight is about 400 pounds in the largest specimens. They have a slender body with large pointed pectoral fins and two dorsal fins.
The lower lobe is smaller than the upper lobe and the tail is relatively large. While they roam the oceans, their tail sways side-to-side and provide excellent swimming power. They contain a pointed snout and large, black eyes that set over their smallmouth.
The blue sharks are very graceful swimmers due to their tapered bodies. The underside of the blue shark is off-white while the dorsal side is indigo-blue colored.
Blue Shark Distribution and Range
The blue sharks are distributed throughout the temperate and tropical waters of the world’s oceans. They are epipelagic species found along the coasts of every continent except Antarctica. They live in offshore waters and occasionally come to the coast, particularly in temperate waters where the divers can observe them.
Blue Shark Prey and Predators
Squid is the most common prey item of the blue shark. They also feed on other species including octopuses and cuttlefish and shellfish such as lobsters and crabs. In some cases, they also prey on sea birds, snatch them from the surface while they rest.
Some large shark species such as the tiger shark and great white shark are the predators of blue sharks. Orcas also feed on shark species. As compared to large adults, young sharks are more vulnerable to predators.
Besides all of them, humans are the greatest threat to the shark species, almost 20 million blue sharks are killed every year by fisheries.
Blue Shark Reproduction
Blue sharks nourish their young in their uterus thus they are called viviparous species. At a time, a female shark gives birth to 25 -50 live pups. In some cases, litters of around 135 pups have been observed.
The length of a newborn pup is around 16 to 20 inches and from the moment of birth, they are independent. The blue shark is listed as near threatened by the IUCN red list of threatened species.
Fun Facts About Blue Shark
i. A shark’s shark
The appearance of the blue shark can be described as the quintessential shark. Their shape is like a torpedo but generally, they are lethargic and move slowly to conserve energy. However, they move very quickly while facing any threat of predator or if they find any prey. Their morphology including their slender body and large tail helps them to swim very fast.
ii. The great traveler
The pelagic blue shark is a great traveler and covers long distances during migration, thus they are found in most temperate and tropical waters. For example, they travel from the water of New England, the USA to South America, which is a confirmed migration pattern of blue sharks.
According to some other studies, they also travel from the west coast of Europe to northwest Africa and across the Atlantic. The total distance is 3,187km from where it was tagged to where it was caught.
iii. An unlikely threat
The blue sharks face the threat of predation from other larger shark species such as orca, and other predators, but besides them, they also have some less expected predators. For example, blue sharks are also eaten by northern elephant seals in Norway. Thus, even for a blue shark, the ocean can be a threatening place.
iv. A smaller problem
Rather than large predators including sharks and whales, the blue sharks have the greatest problem of threat of parasites. A tetrahylidean tapeworm known as Pelichnibothrium speciosum is one such parasite that spends its life in the body of a blue shark.
The parasite enters the body of the shark when it eats an infected intermediate host such as fish. The parasite obtains food and nutrients from the shark and also creates health issues such as digestive problems and deficiency of nutrients.
v. Truly thick-skinned
There are some interesting details about the reproductive behavior of the blue shark and the non-reproductive morphology of the species that may be impacted by this. The males tend to bite the females during courtship rituals and often leave scars.
The behavior is very common and with the help of this, an adult blue shark can be sexed simply by observing the bite marks around its head.
The female sharks have developed a thick skin as an adaptation to withstand this behavior by males and to protect themselves. As compared to the male blue sharks, the skin of females is approximately three times thick.
Blue Shark Citations