The health of a fish or a population of fish can be assessed by clinical history, gross observations, and nonlethal and terminal diagnostic assays (also see Necropsy and Diagnostic Techniques). Regular monitoring of both water quality and fish for problems is the most cost-effective method for detecting water quality and disease issues before morbidity and mortality become evident. A biosecurity plan should be tailored for each individual facility to reduce, control, and eliminate the transmission of infectious diseases and parasites. A biosecurity program reduces the exposure of the aquatic animal by implementing both external barriers (preventing the spread of disease organisms onto and off a facility) and internal barriers (preventing their spread within a facility). Because pathogens can be spread by vectors such as water, equipment, and people, proper disinfection at defined critical control points can greatly reduce exposure.
Vaccination, though not commonly practiced in the USA, can be an important tool to manage fish health. Commercially available vaccines for a number of viral and bacterial pathogens may be administered by either immersion (ie, water bath) or parenteral (ie, IM or IP injection) routes. Other standard management techniques commonly used in aquaculture are weighing (to accurately determine feeding rates and therapeutic calculations) and grading (to sort fish by size at various stages of growth to separate faster-growing fish from slower-growing cohorts and reduce social hierarchal pressures) of fish.
Last full review/revision July 2011 by Stephen A. Smith, DVM, PhD