This revised edition fills the need for an up-to-date comprehensive book on the biological aspects of the bacterial taxa which cause disease in fish. Since the 3rd edition was published in 1999, much has changed in the control of disease of farmed and wild fish. This book analyses all the new information, including that on new pathogens and new developments on long established diseases, such as furunculosis and vibriosis. Consideration is given to all of the bacterial taxa which have at some time been reported as fish pathogens, whether they are secondary invaders of already damaged tissue or serious, primary pathogens.