Is the fish laying eggs or births?

When I was a child, I remember that the fish lay eggs. Later, after raising the fish at home, I found that it was a small fish born in the fetus. So is the fish egg or viviparous?

The mode of fish reproduction can be divided into three types: oviparity, oviparity and viviparity.

1. Oviparity

It is a reproductive way for parent fish to fertilise mature eggs directly in water. In this way, the eggs laid by the parent fish are mostly unprotected. It is often swallowed by a variety of enemies, and the fertilization and development of eggs in water are greatly affected by environmental conditions, so the number of eggs laid by fish in the way of egg laying is more.

2. Oviparity

That is, the egg is fertilized in the female fish and develops in the reproductive tract. In the process of development, the nutrition needed by the embryo body, like the egg laying, is completely supplied by the yolk of the fish egg itself. This way is more evolutionary than egg laying, is not affected by the ever-changing environment, and is more conducive to the protection of offspring. For example, fish such as crucian carp and wicker.

III. Viviparity

Eggs are fertilized and developed in vivo. In the process of development, the embryo body not only depends on its own yolk to nourish itself, but also produces many wrinkles and protuberances on the yolk sac wall to combine with the mother to form a yolk sac embryo disk like the umbilical cord. through this link, nutrition can be obtained directly from the mother. This mode of reproduction, similar to that of mammals, is the most progressive because the fertilization and development of eggs are reliable and guaranteed. Such as gray star sharks and real sharks.