Nonlethal clinical techniques used in the diagnosis of diseases of fish

Numerous nonlethal clinical techniques can be used on live fish to yield valuable diagnostic information. These techniques include skin, fin, and gill biopsies; bacteriologic cultures of gill or skin lesions; tissue and fluid aspiration; and radiography Most techniques can be performed on live fish without the use of anesthesia, although light sedation of the fish often simplifies the procedure, making the procedure more easily accomplished and less stressful on the fish. Because water conditions have a considerable effect on the health and well-being of aquatic animals, an in-house evaluation of water quality (eg, temperature, pH, ammonia, nitrites, nitrates, and salinity) is also paramount to any clinical diagnostic evaluation. As with domestic animals, a complete and accurate history and thorough external examination are prerequisite to the selection of appropriate diagnostic techniques as well as the formulation of any management or therapeutic plan. Through the correlation of clinical history, water quality variables, and results of diagnostic testing, an informed plan of action can be devised to correct acute or chronic problems in aquatic animals.