What is this fish that looks like a common roach with black eyes and red gills?

Question

Fish like this have been caught recently (this Autumn) in many freshwater bodies in Sweden (like Dalbergsån) and no one knows what they are supposed to be (as written in this article). Apparently, the fish was caught on worms.

It looks like a common roach, but the eyes are different colour and the red around the gills is uncharacteristic. Some pictures I have seen show a yellowish hue on the fins. I'd guess it is an invasive new species and probably someone out there knows what it is.

Here is a gallery with other images.

Answer 1

Well, it seems that the mystery was solved: it is a common roach with a guanin deficiency that causes them to have a different colour, as explained by this ecologist (in Swedish).

Answer 2

After netting one of our stock ponds, for a stock check. We discovered these two beauties in the net, the pond had a mixture of species, Carp, Tench, Roach and Rudd. I’d never seen anything like them before, I placed them in a holding tank while we continued with the netting. I took some pictures and emailed them to some friends within the industry to see what they thought.

A few days and several referrals later. I received an email confirming that they are Roach with a pigmentation disorder, he said we are lucky to have them as they are very rare. He has worked on a fish farm, supplying freshwater species for restocking rivers and lakes for over twenty years and hasn’t seen one in the flesh before.