Size:

Blue sharks can reach lengths up to 3.8 m. Average-sized sharks are smaller, more like 1.8 to 2.4 m. A blue shark can weigh up to 200 kg. Pups are 48 cm long at birth.

Diet:

Blue sharks eat almost anything. They eat fish and squid. But they also eat small sharks, seabirds, and garbage.

Enemies:

They are eaten by bonito sharks and other large sharks. The California sea lion has been seen eat by blue shark.

Habitat:

Blue sharks live in temperate and subtropical waters.  They are found at the surface down to 350 m.

Bibliography: http://new-brunswick.net/new-brunswick/sharks/species/blue.html