There are relatively few species, although members of this group are abundant. Chambered Nautilus Squid Cuttlefish Fish are the dominant nekton. They are distributed world-wide and can occur at all depths. Cartilagenous fish . Sharks are wide-spread, epipelagic members of this group.
Most sharks are active predators, some of the large varieities are actually plankton eaters.
Skates and rays are also cartilageneous. They inhabit the bottom of shallow sea-floor. Bony fish . . Large mouths, well-developed teeth to ingest the unpredictable sinking of food particles or encounter with a prey. Low rates of metabolism.