Extremely variable by type of fish.
Rabbits are ready to breed when they are between the ages of six months and three years. Also, a male rabbit will make noises with its nose and circle you or the female when he is ready.
i dont exactly know how to anwser this but fish and rats tend to breed every quickly and rappitly
When a duck is ready to breed, I find it will get "flirty" around other ducks. They stay very close and bob their heads in a slow or very fast way, and nuzzle the other ducks with their beaks. If you have male and female ducks, you don't really have to know, they will know themselves and breed when they are ready.
the male would be skweesing out the eggs of the female and when the egg get sqused out they would flout up to the top of the tank on the bubble nest that the male made when it was ready to breed
they have white spots on them when they want to breed. NO YOU CAN'T MAKE THEM BREDD LET THEM DO IT ON THERE ON.
When they start having offspring.
Maybe they do and you just don't know it.
no Edit: Whoever answered that doesn't know the game. Yes, you can.
well im not entirely sure but i don't belive any freshwater fish are easy to breed. I would not recomend breeding fish unless you do the proper research. you have to know what your doing. if you already did your research the find a breed that you like and breed um up.
You can only tame an ocelot with fish and it the only why to breed cats (as I know of.)
see related question below that might help answer your question How do you know when a ferret is ready to breed?
The doe is always ready to take the buck. Hense why they breed so much