It's a survival thing. Many eggs are eaten before they have a chance to hatch. Many are eaten shortly after hatching. The chances are that 9 of 10 won't make it the first week, then even if they do, their chances of survival diminish quickly.
A broadcast spawner would produce many smaller eggs and an egg guarder would produce fewer but larger eggs. Thus the broadcast spawner produces more eggs.
Fish
Reptiles are more closely related to mammals than to fishes. Reptiles and mammals are both part of the group called amniotes, characterized by their ability to lay eggs on land. Fish, on the other hand, are a separate group with distinct evolutionary lineages from reptiles and mammals.
First of all there are only two mammals in the world that lay eggs: the Platypus and the echidna. The size ratio from the size of a fish to the size of their eggs is much bigger then either of these two mammals. So looking strictly at the amount of eggs that these animals can have, the fish has the advantage. Also, Both of these mammals don't have many predators because of their advance defenses. A platypus has spurs on its ankles that can deliver a deadly toxin and the echidna is a glorified porcupine! So, they don't necessarily need to reproduce quickly. Whereas a fish has an infinite number of predators and they rely on their ability to replenish their population to prevent extinction.
no
Platypuses and echidnas are the only mammals that lay eggs. These mammals belong to the group of mammals known as monotremes. Platypuses and echidnas lay eggs just once a year. The platypus lays 1-2 eggs, while the echidna lays a single egg each year.
Reptiles are neither mammals nor fish. Taxonomically, they are more closely related to mammals.
Do you mean "Why do fish lay so many eggs at one time? The reason fish lay so many eggs at one time is survival. The more eggs that a female lays the better chance more eggs will have a chance to survive.
If there is a decline of some fish population government proclaims fishing quotas for that species. So there is less fishing, fish can lay more eggs and produce offspring. And hopefully in next generation produce more fish.
Because they only can produce little offspring, unlike fish who produce millions of eggs and fertilize them afterward. Also, reptile and bird egg shells are tough making it hard to fertilize when fish eggs are more like jelly.
because fish eggs are so small, fish can fit more eggs in the womb.
Fish