Scientific name:
Prionace glauca Identification:
Long snout; long, narrow pectoral fins; eyes relatively large; dark blue dorsally, lighter ventrally. Size:
Birth 40 cm (15.7 inches), maximum length 3.8 m (12.5 ft). Range:
Circumglobal in tropical and temperate seas. In more tropical areas they are found at greater depths (tropical submergence); for example, in tropical Indian ocean most common between 80-220 m (264-726 ft). Depth range from surface to 220 m (726 ft). Biology:
Oceanic, but sometimes they move inshore near offshore islands where they have been observed in kelp beds. Feeds heavily on smaller prey (krill, squid, schooling fishes). The gill rakers have elongate papillae that apparently prevent smaller, slippery prey from escaping out of the gill slits. They also eat small sharks, sea birds, and mammalian carrier. More active at night; around the Channel Islands off California, it moves into shallow inshore areas at night, possibly in response to changes in prey distribution. In the north Atlantic blue sharks make regular dives, from the surface to depths greater than 400 m (13,200 ft). These vertical movements usually occur several times each day and occur most often during daylight hours. Usually curious of divers, but not aggressive. In baited situations it has bitten divers.