Most fish lay eggs, and it is fertilized outside of their body. Fish that spawn, are called oviparous. But some fish give birth to live fry. Such fish are called viviparous.
To live-bearing are guppies, sword fish. The eggs of these fish are fertilized inside the mother’s body and develop there until the fry. At a certain time they are born. This happens 21 days after fertilization.
The number of eggs, fertilized and deferred, differs greatly depending on the type of fish. Some fish lay eggs and abandon her, without showing her any more interest. This is a fish that produce huge amounts of eggs. Those fish that look after their young, they lay only a few eggs.
Caviar can be of two types. One kind of eggs floats on the water surface, the other sinking. The caviar, which floats, is called pelagic. It is usually tiny, bright and contains a lot of protein. Caviar, which is sinking, is called Donna. It is usually harder and more protein in it. Continue reading
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
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