The crucian carp is a tenacious fish which prospers even in wintry, low oxygen water conditions, as it is able to produce oxygen by using the sugar reserves of its liver. This process also creates alcohol but has had no adverse effect on anglers! Crucian carp are often the only fish in ponds where other fish have departed. Up to 40 centimetres long, it is a close relative of the gold fish common in aquariums. There are also lake and pond forms of the crucian carp, but they are actually the same species. Its size depends on the amount of nutrition it is able to attain; it is usually able to obtain the greatest amount of food in large lakes. Apart from lakes and ponds, it also inhabits the southern coastal waters of Finland.