How Fish live

A fish is a cold-blooded  creature which breathes in oxygen extracted from the water, not form the air as on the case of mammals .there are three classes of fish and they are primarily differentiated by the of skeleton that they have. Most British fresh-water fish (including rainbow trout, and teach have) fall into the third group skeleton, while those of the other classes have cartilage skeletons, with jaws some cases and without in others. Many o f these fresh –water fish with skeletons of bone structure have swim bladders, the function of which is discussed overleaf.

Body shape of fish :

There are great variations in the body shape of fish over the whole range of species. The most usual, however, is a streamlined one like that of he typical fish. Certainly this is approximate shape of rainbow and teaches

How fish move :

As mentioned before, some fish have a swim bladder, which is situated in the middle of their body. It is a silvery, gas –fish bag which, permitting a fish to float and swim at any depth in the water without rising or sinking. Any fish that have not got this organ must keep on the move continuously.

A fish can follow any course it wants through the water by using its fins. Two pelvic and each of dorsal, caudal (or tail) and anal fins. this, however , varies form species to species and some fish lack pelvic or pectoral fins, while others lack a dorsal or caudal fin . in some  instances several fins are amalgamated. An example of this is in the eel, whose very long dorsal and anal fins merge with the caudal fin, giving a continuous edging so fin along the whole body. The fins control stability and direction.

The senses :

Fish have eyes with a very wide range of vision. Between the eyes and the mouth, on the uppermost side of the head, are two small vents –nostrils, but the fish does not breath through these. Instead they are used for smelling only and have nothing to do with the respiratory system.

There is a faint line running on either side or the body of a fish, which is known as the lateral line. This consists of a series of highly sensitive cells, which, by means of records of pressure, indicate distances and warn of hazards. It is, in fact, a built in radar system. In addition, some fish have barbells, which are fleshy filaments hanging from their mouths, which they as feelers.