Whitefish is a polymorphous species that has several different sub-species living in different environments. Whitefish is a headache for researchers, and a favourite among fishermen. In the last century whitefish have been divided into countless species, sub-species, forms and races. A full understanding has still not been reached. The difference between vendace and a small whitefish is that the upper jaw of whitefish is longer than the lower jaw, whereas it is vice versa for vendace. Whitefish feed on, to some extent depending on sub-species, either bottom animals or small crustaceans. Whitefish spawn in the autumn; ground whitefish spawns on the cost, common whitefish migrates to rivers, humpback whitefish, houting and muksun spawn in both rivers and in lakes. Whitefish is found everywhere in Finland in cool water rich in oxygen. Whitefish is a very varying fish also in what comes to growing. Even different whitefish forms living in the same water may grow in completely different ways. At best, a whitefish can weigh 12 kilograms (or 26.4 pounds).