Thirty years after the cage aquaculture industry in Europe began, the industry has matured. The main species in northern Europe are the Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). The majority of production is in Norway, Scotland, Ireland and Faroe Islands. However, also countries as Finland, Iceland, Sweden and Denmark have a cage culture industry. All relevant aquaculture production using cage technology in northern Europe is carried out in marine waters. The production volume in 2004 is about 800 000 tonnes of Atlantic salmon and about 80 000 of rainbow trout. The production volume of Atlantic salmon is expected to grow further, while rainbow trout for the moment shows a negative trend. There is an increasing interest to expand the production of other species, such as cod and halibut.