How to reasonably calculate the number and size of eggs laid by fish

Many people have seen fish spawning, but few have paid attention to the number of eggs each time. The general feeling is that the number is very large. Generally speaking, fish that protect their eggs less, suffer greater losses, and have a low survival rate for young fish will spawn a lot; conversely, fish with protective habits will spawn fewer eggs. For example, sticklebacks only lay 80-100 eggs; minnows lay 200-300 eggs; silver carp can lay 500,000 eggs; grass carp lays 400,000 eggs; and eels can lay 10 million eggs. The reason why fish spawn in large numbers is to increase the number of surviving offspring and spread maternal genes as widely as possible.

Generally speaking, if the size of the eggs is larger, the offspring will also be larger, so that the offspring has a higher survival ability. But why don't many fish concentrate their reproductive investment and try to lay large-sized eggs to ensure the survival rate of their offspring?

The size and quantity of fish eggs are the best model summarized in the process of reproduction from generation to generation and in the development of evolution. Organisms need to spread their genes as widely as possible. For species with strong spawning ability, if the size of the eggs is large, the number will be too small. Even if the survival rate of the offspring is high, it is not cost-effective. However, if the size of the eggs is too small, the survival rate is too low. Therefore, they must find an optimal solution between the size and number of eggs to ensure the maximum number of surviving offspring. This optimal size of eggs is most conducive to the reproduction of more offspring and can widely spread its genes.

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