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.