Do all fish spawn?
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.
For example, the herring lay demersal eggs and doesn’t show her no attention at all. It can produce from 20 000 to 40 000 eggs. Cod, on the contrary, lays pelagic eggs. Cod of medium size throwing a hundred million eggs!
The season for mackerel lays from 400 000 to 500 000 eggs, but at one time 50 000. A big halibut can give more than two million eggs.
The eggs differ in size. The egg of the herring in diameter of 1 mm cod — 1.5 mm, halibut — 3 mm. of the Eggs that are protected until it appears the fry are more likely to survive. But millions and millions of eggs are eaten by other fish and marine life.
Why spawning salmon swimming upstream?
Many animals, from our point of view, give birth and protect their young very strange. In the end, isn’t it amazing how birds build nests, or how some animals are willing to fight to protect its offspring from enemies?
The instinct that compels salmon to make the long journey upstream, due to the fact that this is the best way to produce calves and raise them in safety. Not all members of the salmon family rise far upstream to spawn. Some remain below. For example, pink salmon. He spawns just a few miles from salt water. For contrast: the Royal salmon can swim about 5 kilometers from the sea up the river.
Fresh water is the most favorable conditions for salmon, where he becomes healthy, strong and thick. But once in fresh water, he stops eating. Sometimes the salmon is completely exhausted, trying to reach where he wants to spawn.
Since many of the rivers on which they sail, there are rapids, waterfalls and rocks, salmon often loses weight and looks very bad to the point where it begins to spawn. But regardless of whether he is exhausted or in great shape, Pacific salmon persistently moving towards the spawning ground. When the fish gets to the place (usually the same where she was born), the female drills a hole in the shingle or sand, using his body, tail and fins. Then it lays its eggs in this nest, and the male fertilizes it. Then the female buries the eggs.
When finished, the salmon will lose all interest in life. They drift downstream and die soon. Now begins the life of the newborn fish, which hatch after about 60 days.
Young salmon remain in freshwater for a few months or a year, and then descends downstream in the sea. And the cycle begins again.