The fish are vertebrate animals which live in water. A great quantity of small fish feed from insects which fall into water, and some are captured by leaping out of the water. Naturally many other fish smaller than they eat algae.
The fish breathes using gills, usually located on the head, behind the mouth. The gills capture the oxygen from water when the fish is moving. Water enters the mouth, passes in the gills and leaves by the gill slits. In this way, the fish can open and close the mouth to make circulate water in the gills without having to move.
The fish are cold-blooded animals, some can live in very cold water. Some are only adapted to warmer climates.
In the same way, most of the fish which live in fresh water cannot survive in salt water. The fresh water fish cannot live in ocean water.
Fish lay eggs to reproduce, and it usually lays a great quantity to ensure the survival of some individuals. Certain fish, like salmon, will die after spawning. Often spawning time, or mating is done at the same place, and fishing is often prohibited there during this period. To harvest fish during this closed season is considered poaching.
The fish swims using fins and its tail. The tail is its principal engine, the fins being used to stabilize it. Certain fish have spines on certain fins, often the dorsal fin, as means of defense. The skin of fish is made scales.
The fish are adapted to their environment. Those which live with very great depths have almost useless eyes, but will use the vibrations to detect their prey. The flounder has the two eyes on the same side of it's head because it lies flat at the bottom. Like the terrestrial animals, the fish underwent the natural selection and some acquired specialities.
Certain fish are the predatory, like the pike. They have usually a mouth equipped with teeth, which opens with the front of the head. Others have the mouth placed below the head because they eat what has settled out of the water, like carp.
Fish is a large source of food for many animals, that is the reptiles, birds and many mammals. Water in which they live is like our air, and the water pollution harms fish enormously. It is necessary to avoid polluting the rivers and complying with the rules of fishing. |
