Question

How can we say that fish exhibit external fertilization?

Answer 1

External fertilization occurs when both sperm and eggs release into an external environment. In which the sperm reaches the egg ,then fertilization takes place. It occurs during the process of spawning where one or several females release their eggs and male release sperm in the same area at the same time.

Complete answer:
To answer this question we must know about the method of fertilization in fishes.
Fertilization is external In most of the fish species. Large amounts of eggs and sperm are released into the water by females and males and the process of egg release is called spawning. During spawning, numbers of species will come together to form an enormous group, and all release their eggs and sperm at the same time. The reason behind fish exhibits external fertilization.
The sperms swim randomly in water and come in contact with eggs. Then the nucleus of the sperm moves into the egg and fuses with it. And it occurs outside the body that is why we can say fish exhibit external fertilization.
As the fertilization occurs in the external environment therefore we can say that fish exhibit external fertilization.

Note:
External fertilization allows the female to select a particular male and fertilization in aquatic environments protects the eggs from drying out. The presence of the fertilized eggs and developing young in the water provides opportunities for predation, resulting in loss of offspring. The offspring produced by this method must mature rapidly.