The knowledge of isolation and identification of bacteria from aquatic animals and the aquatic environment is expanding at a rapid rate. New organisms, be they pathogens, environmental, normal flora, or potential probiotics, are being described and reported each month. This has resulted due to increases in aquaculture research, in intensive fish farming systems, and in the international trade of live aquatic animals and products as well as the emergence of new diseases. This manual provides a source that enables the identification of bacteria that may be found in animals (particularly fish) that inhabit the aquatic environment. The emphasis is on bacteria from farmed aquatic animals.