I fly fish on a small lake in Winchester that is fed by the Itchen. Carp have entered the lake during floods and seem happy there. Almost any kind of small nymph or lure on a slow retrieve might be hit by a carp. Epic fights on light fly tackle. I think it shows that carp will eat fry and any other naturals when they can't get bait.

I first witnessed carp feeding on rudd back in the 90's, not fry, rudd of 4-6ins vanishing straight down the throats of mid-doubles.
Since then I've seen similar on many occasions. I've regularly watched rudd feeding on their own fry as well.