Why do so many fish eat their own fry, even when food is plentiful?

Question

No, fish eat their own eggs even as they are falling after just being laid!

Answer 1

fish are bad parents.

Answer 2

to separate their weak from their strong, thus maintaining the species strength

Answer 3

they most certainly do eat their fry, as do Platies, Swordfish, Mollies, & the other common livebearers. However rather than separating them, which is stressful to the fish, your best bet is to include lots of plant material for the fry to hide in.

Guppies breed so frequently & produce such large amounts of fry, that unless you're in the purebred Guppy breeding business, having some of the fry provide some live food for the parents isn't really a bad thing. With enough plant material (planted & floating), you should still end up with enough babies to enjoy growing on into adults without overpopulating your tank too soon.

the males preferred to eat larger eggs — which take longer to hatch — from the second female they spawned with. They conjecture the fish do so to cut down on the amount of time spent caring for their young, thereby enabling the dads to reenter the mating game sooner.

Sand goby dads have to care for thousands of eggs "until they hatch — about one to two weeks — and during this time he isn't able to attract any new females," Klug explained. Eating his young might "allow him to increase the total number of offspring he produces over the breeding season."

they could be weeding out inferior offspring, or they could very well be hungry.

Answer 4

  Fish will eat anything they can swallow.

  In the case of their own offspring something prevents the mother from eating the young at least in the early stages.

  Once the young leave home they are strangers and the mother will eat them.