The Baltic Sea 64 Infectious Diseases Viral Diseases Infectious Pancreatic

Introduction Fish has an enormous value as the most frequent source of animal protein for the major part of the humans, especially in countries during rapid development in Asia and Africa. All fish species are a part of the local ecology and as such has a biological and environmental importance. Fishing also gives a great pleasure to sport fishermen around the world and at the same time contributes to the local economy. In spite of this fish receive very little attention in consideration to diseases and health protection especially in regard to feral populations. These populations are often very vulnerable and to promote sustainability it is of outmost importance to take active actions and promote international regulations for restrictions of fisheries. Fish is a difficult group to handle regarding welfare, diseases and health protection. The reasons for this are several but the most important are: • Fish lives in water – and water is an excellent medium to transfer pathogens from one area to another, which contributes to a fast and uncontrolled transmission of infectious diseases. • It is often difficult to recognise clinical signs of disease in fish since they lives in water. Fish also lack mimic, voice or recognizable body language, which gives a late discovery of the disease and restrain a fast starting up of the treatment.