Simple biology questions help!!!?

Captive breeding is breeding in captivity, so like in zoo's where the animal is not in its natural environment. a disadvantage of using only one male is a lack of diversity in the gene pool, meaning that its offspring with the other females will all be related, being either half or full siblings they wouldn't be able to mate with each other. Also if you've only got one male there could be chance that the male won't be fertile and produce no offspring. They might not breed in captivity because they could be stressed or unhappy, the environment is not natural so they may feel it unsafe breeding, in nature being pregnant or looking after the young puts you more at risk from predators so its important that they feel safe, birds for example nest high up in trees or cliffs not in bird cages. Also being in captivity they may not have learned all the skills that they would have acquired in the wild, including mating rituals etc. Oh and I've just learnt that goldfish like to eat their own eggs and baby goldfish which is an example of why goldfish don't breed successfully in a goldfish tank.