A European freshwater fish with a bluish green body?

There are several European freshwater fish with bluish-green bodies. To narrow it down, I need more information! Can you tell me:

* Where in Europe is the fish found? (Specific country, river, or lake)

* What size is the fish? (Small, medium, or large)

* What is its shape like? (Slender, round, flat, etc.)

* Does it have any other distinctive markings? (Spots, stripes, fins, etc.)

With more details, I can give you a more specific answer.