It is now ten years since the last edition of this classic text appeared, since when the growth of salmon and trout culture around the world has led to the emergence of many new and distinctive problems. This new third edition is greatly revised, with considerable use of colour illustrations, and provides a wealth of information hitherto unavailable to the farmer on new diseases and on new problems with older ones. It also addresses the newer production technologies and their diseases problems and the new treatments such as vaccines which were merely promising research topics when the last edition was produced. This text is the product of fifty years' combined experience of the salmon farming industry by two veterinarians who have been involved from the very start.