The blue shark is known for its beautiful coloring and its swimming ability. Its scientific name, Prionaceglauca, comes from Greek words meaning “saw,” “point,” and “blue.” Its other common names are blue dog and blue whaler.
The blue shark is considered dangerous to humans. There have been documented attacks on both people and ships. Blue sharks are known to circle shipwreck victims, sometimes for up to 15 minutes. Although not considered an aggressive species, they will attack!
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Habitat
Blue sharks have a broad range. Some scientists regard them as the most widely distributed of all shark species because they are found in so many different areas of the world. The only coast they are not found off of is Antarctica!
They are found in both temperate (mild) and tropical (hot) waters. Their favorite temperature is between 45-60 degrees Fahrenheit. They are also a species that prefer the open ocean but have been known to move closer to the shoreline at times.
Size/Color
The largest blue shark ever recorded was a little over 12 feet long. The average blue shark is between 6 and 10 feet with a weight of between 300-400 pounds.
Blue sharks have a distinct blue color with a crisp white underbelly. This color contrast on top and bottom is known as countershading. The sharks have a darker blue shade on their back and a brighter blue hue on their sides.
Anatomy
The blue shark possesses a slender body and sometimes gets mistaken for pups of other shark species. Its tail fin is a unique shape, with the top part of it being much longer than the bottom part. Put together, the blue shark’s body and tail shape not only give it an elegant appearance but also enables it to swim fast and be quite acrobatic.
Diet
The teeth of a blue shark are serrated and face inward, allowing it to eat many different types of prey. The blue sharks’ favorite meal is squid, but they will also eat items commonly found in a human’s idea of a seafood buffet, such as shrimp and lobster. Bony fish, other sharks, and sea birds also find their way into their stomachs. Blue sharks take advantage of any food they can find and have been known to eat from fishing nets and dead marine animals. They are known to eat so much that they come close to bursting!
Special Adaptations
The gill slits of a blue shark are specially adapted to ensure it can eat even the smallest of sea creatures. They contain special finger-like projections that block the escape of prey through the gill slit. This allows blue sharks to feed on tiny sea creatures such as anchovies and krill, tiny creatures similar to shrimp. This technique, similar to what a human could do with a straining net, enables the blue shark to take advantage of small creatures other shark species cannot eat due to the size of prey.
Reproduction
Blue sharks are viviparous and give birth to live babies called pups that have been carried inside the mother. Female blue sharks carry babies for anywhere from 9-12 months. The size of the litter is believed to be related to the size of the mother. Litter sizes have been reported from 4-134 pups. The average size is 25-50 pups at one time. After birth, the baby sharks are on their own immediately.
Conservation Status:
Blue shark populations are affected by sports fishing and some commercial fishing. As with other sharks, their fins, skin, and other organs are harvested for human use. Despite its population abundance and wide range, there is cause for concern about overfishing. They are currently listed as Near Threatened.
Fact Attack
- Scientists have studied tagged blue sharks and discovered they are the nomads, or travelers, of the sea. Blue shark migrations are common from 1,200 to 1,700 miles. The longest recorded migration of a blue shark was from New York to Brazil ~ a journey of 3, 740 miles!s.
- The blue shark is one a few species that migrate, or move, in groups called schools or shoals. These groups, when mixed, are all ordered by size or gender with every shark in its specific place. Sometimes, there are only all male or all female groups!
Resources
http://marinebio.org/species.asp?id=35
https://www.floridamuseum.ufl.edu/fish/discover/species-profiles/prionace-glauca
http://www.arkive.org/blue-shark/prionace-glauca/
http://www.discoveryuk.com/shows/shark-week/sharkopedia/blue-shark/
