They eat easily a 12" fish. Usually more than 2 pounds of fish/day/bird.
Some years ago 5 cormorants in 3 months eat more than half of my 1"-12" fish and killed almost all the biggers. I found many of them dead with lateral wounds due to cormorants pecks. They attack every fish. If it's too big to be swallowed, they leave it dead or seriously injured.
I've tried many legal way to keep them away from my pond, but they have been unsuccessful, more or less.
The only thing I've found successful (first year) is a sort of web made with some thick fishing line. Not a single cormorant in my pond since fall. They fly over my pond everyday but no one comes down.
