Bream
Breams (Lahna in Finnish) are one of the most common catches while fishing. You can get anywhere between 1 - 12 breams in a net. However, breams are not that large. They only weigh around 0.5 lbs but are very nutritious.
URW Game Encyclopedia description
The official URW in-game encyclopedia (accessed by the F1 key) doesn't have a separate entry for the bream, but in the entry on Fishing, it mentions the bream and bream-fishing in the following paragraph:
The fish to be caught depends on the fishing method, equipment and the fishing site. Different kind of fish live in shallow or deep waters, lakes or rivers. Perches, roaches, breams and pikes are the most common fish living in lakes. Salmons are found only in rivers, and especially in rapids during their spawning season. There are also lavarets, trouts, pike-perches and so on.