Hundreds of thousands of years ago, long before the appearance on Earth of man, the oceans already swam fish. At that time they were the most highly developed creatures.
Since then, they began to develop a variety of ways so that now only some species only vaguely resemble the first primitive ocean fishes.
As a rule, fish has an elongated and tapering shape. People have copied it in the construction of ships and submarines, as it is the best adapted to movement in water.
Most fish use their tail as a motor. With the help of fins and they control their movements. Except for one species of fish, all the others breathe by means of gills. Fish swallows mouth water that passes through the gills and out through the hole. Water also contains oxygen, and it through the gills into the blood of fish, as the air through the lungs in the blood of man. Continue reading
Floating jellyfish in the sea often struck by its beauty. Such a wealth of shapes, colors, as among the jellyfish, not to meet many animals! Jellyfish inhabit all seas, and some of these sea animals prefer warm waters of the tropics and subtropics, while others liked the cool Northern parts of the oceans.
Some jellyfish can be found at a depth of 10km, and there are jellyfish that do not leave the coastal strip. It is noteworthy that each type of jellyfish is found only on the territory of the area is an animal does not apply to pandemic, that is common everywhere.
The largest jellyfish is Cyanea arctica – chosen by a cool North sea. The age of lanei can be identified by its colour – older individuals are covered with brown and red spots; the young specimens are painted in an intense orange color. Continue reading
Typical representatives of the nekton is the herring. It is well known that this fish has great commercial value. Until comparatively recently, it was promyshlyali in such large quantities that its price was very low, despite excellent taste and nutritional quality. In recent years, due to the sharp increase of the fishing fleet and introduction of intensive methods of production occurred overfishing. The number of herring in the oceans have decreased dramatically.
If in the future the intensity of the herring fishery will increase or even remain at current levels in the coming years, this valuable food fish will become a Museum rarity. Reduction of stocks of herring and concerned consumers and fishermen, but the first sounded the alarm scientists.
The appearance of the herring is well known to everyone, but it is unlikely that the layman can easily distinguish one kind of herring from another: the difference between them for the untrained eye to be insignificant. Species differences are not only in the details of the structure and the size of the fish, much deeper than they differ from each other in biology, numbers, distribution. Therefore, the fishery for mackerel fishes should be strictly subordinated to scientific data, to each type needs special approach. Continue reading