FISHES

Marine fishes (species of fish) include 3 of the 7 classes of vertebrates. Typically they live and grow in water, swim with fins and use gills for respiration. Although the early evolution of fish broke off into 3 directions, only 2 play major roles in present day marine communities. One branch went bony, the other went cartilaginous. Bony fish, class Osteichthyes, have great maneuverability and speed. They have specialized protrusible jaws, which enable them to eat larger prey and a swim bladder which allows them to stay motionless at any depth. They have a lateral line which detects low frequency sounds and water pressure. This is how schools seem to move in a particular direction all at once. Cartilaginous fish, class Chondrichthyes, sharks, rays and chimaeras do not have the calcuim-rich, vascular, strong tissue known as bone in their skeleton. As a group they tend to be larger in size than the bony fishes and lack the characteristic scales. Fish also have electroreceptors which detect the electromagnetism of other animals and chemoreceptors which detect smells and taste.