Our planet is inhabited by almost 20 thousand species of fish. About 1/10 of them are commercial. They give people a lot of valuable products: food, medicines, fertilizers for the agriculture, pet food, industrial oils, raw materials for light industry.
To move in the water, have to spend a lot of energy. Nature took care of the fish, giving their bodies zaradougou streamlined shape. The speed of the fish (scombridae, tuna, sharks) in its form and speed resemble that of a torpedo. The fastest fish is considered fish-sailfish, swordfish and Marlin, which reach speeds of up to 130 km/ h. The rate of freshwater fishes is typically lower, but in critical moments of his life, in the moment of impending danger or in the event of an attack on their prey, they can take a short term shot at a speed of 1-2 km /h. Good speed swimmers usually are found in rivers with current (sabrefish, Chub, nase, Dace, salmon). The speed of the fishes living in stagnant water far below, but they are more nimble, nimble (carp, bream, Rudd).
Fish are divided into peaceful and predators. Predatory fish (like all predators) it was their mouth, powerful jaws and sharp teeth. Amazing device the teeth of a pike: they are able to thibetica back when swallowing. Very big mouth (in his head) catfish,burbot, Zander. The fish that are looking for salepropecia on the bottom and dig the soil, pull-out mouth. The food is small and mouth is small, and most of the upper is that the fish whose lot of small organisms ( sabrefish, vendace, bleak, Zope).
Coloration in nature for the majority of living organisms has the masking value. Here and fish: peaceful “hiding” from predators, and in turn, the camouflage needed to pass the victim to hunt down.
Therefore, most freshwater fish are dark-colored back (when viewed from above it blends in with the dark bottom) and a bright abdomen (at the bottom merges with the sparking surface of the water). Bottom fish is often painted in nature color of the bottom or less – have spotted coloring; which changes the appearance and distorts the contours (burbot, catfish, sculpin is one of them). The inhabitants of the thickets of color with the same purpose often striped.