Blue Shark

Average size between 250 cm and 300 cm, maximum total length about 380 cm. Slender, with long pectoral fins. Narrow head, with a parabolic snout (from dorsoventral view). Big eyes, without posterior notches. No spiracles. Origin of first dorsal fin behind the free ends of pectoral fins. No interdorsal ridge. Small keels on caudal peduncle. Displays a intense blue upper body, white ventral surface. No color pattern.

This species prefers colder waters but tolerates warmer water too. Blue sharks normally swim very slow at the surface but can be found down to a depth of approximately 150 m. Males and females live segregated. Aside from the Oceanic whitetip shark , and the Silky shark , this is probably the most abundant offshore species. Blue sharks seem to migrate clockwise with the Gulf Stream and some have been tagged (marked) in US waters only to be recaught in Spain. Others have been tagged in the Canary Islands and were recaught in Cuban waters. Feed primarily on small fishes, as well as invertebrates and carcasses. Blue sharks possess papillose gill rakers, a rare feature among requiem sharks. This may prevent small prey like squid, red crabs, or anchovies from slipping out the internal gill slits, or may be used to feed on plankton too.

Gives birth to live young (viviparous wih a yolksac-placenta). Up to 130 pups per litter but normally between 25 and 50 pups. Pups show a fast growth rate. A possible reason for a fast growth rate may be because they are born in open water with no protection. The high number of pups and no interruption in the reproduction cycle of females seem to support this hypothesis. Blue sharks reach sexual maturity at 5 to 6 years of age and at a size of about 180 cm (males) and 220 cm (females). Females have a much thicker skin than males, approximately 3 times as thick. The thickness exceeds the length of males" teeth so they are not able to penetrate the skin while holding the females with their teeth during copulation. Females can store sperms even in a immature state and can fertilize the eggs in the following spring upon reaching maturity.

Appearance

Biology

Reproduction