AQS406 FISH DISEASE
Having in mind that fish diseases, caused by bacteria, viruses, parasites or fungi represents factors that can have significant negative impact on aquaculture (Kabata, 1985), the appearance of a disease can be even more devastating for the aquaponic systems. Maintenance of fish health in aquaponic systems could be more challenging than in aquaculture, and one of the main challenges to successful aquaponics operation is connected with disease control (Sirakov et al., 2016). Diseases which affect fish can be divided according to the origin in two categories: infectious and non-infectious fish diseases. Infectious diseases are caused by different microbial pathogens transmitted either from environment or from other fish. Pathogens can be transmitted horizontally (between the fish) and vertically (within eggs). Most common causative agents of infectious diseases in aquaculture are bacteria (54.9%), viruses (22.6%), parasites (19.4%) and fungi (3.1%) (McLoughlin and Graham, 2007). Often, although clinical signs or lesions are not present, fish can carry pathogens in in a subclinical or carrier state (Winton, 2002). Fish diseases can be caused by ubiquitous bacteria, present in any water containing organic enrichment. Under certain conditions, ubiquitous bacteria quickly become opportunistic pathogens. Presence of parasites on the gills or skin, as long they are present in low numbers, usually do not lead to significant health problems. Capability of pathogen to cause clinical disease depends on the interrelationship of six major components related to the fish and the environment in which they live (physiological status, host, husbandry, environment, nutrition and pathogen). If any of the components is is weak, it will affect the health status of the fish (Plumb and Hanson, 2011). Non-infectious diseases are usually related to environmental factors, inadequate nutrition or genetic defects (Parker, 2012). Successful fish health management is accomplished through disease prevention, reduction of infectious disease incidence, and reduction of disease severity when it occurs. Avoidance of contact between the susceptible fish and a pathogen should be a critical goal, in order to prevent outbreak of infectious disease.
Three main measures to achieve this goal are:
use of pathogen-free water supply
use of certified pathogen-free stocks
strict attention to sanitation (Winton, 2002).