Well I don't know either answer right off but I believe there are plenty of species that are actually protecting a increasing the chances of their fry, despite eating other of their fry. The act of eating ones own fry actually serves two purposes: first, by eating some of the fry, the fry that aren't eaten get more food and have a better chance and they are usually the more viable fry. Secondly, the parents retain some of the valuable protein their bodies have spent energy making, so they are more viable and competitive for having their next brood.
WD