Unidentified fish

Unidentified fish

Observation - Unidentified fish - Global. Description: My friend James has been keeping a particular type of fish for the last 6 months. He found them in a large pond/small lake in France which had been frozen the week before he began fishing there. He brought the fish back to the UK. They are very hardy fish

My friend James has been keeping a particular type of fish for the last 6 months. He found them in a large pond/small lake in France which had been frozen the week before he began fishing there. He brought the fish back to the UK. They are very hardy fish and will not eat anything except for live or frozen food. They have 1 dorsel fin like a sicklied. These fish are quite aggressive and for some reason attack other fish by eating their eyes. Enquiries have been made as to what type of fish they might be at pet shops and a Marine Biologist but nobody seems to have seen them before or know what breed they are. Can anyone identifiy the fish in the attached photo?