The topic provides an introduction to aquatic parasitology in order to ensure a basic knowledge of the wide variety of fish parasite pathogens. Sufficient knowledge of their taxonomy, morphology and lifecycle strategies will be provided to identify pathogens in aquaculture and fisheries. Knowledge of specific parasitic diseases encountered in freshwater culture, both tropical and temperate, will be provided as well as those in mariculture. Although the topic is predominantly focussed on diseases of cultured fish, parasite problems in fisheries and in ornamental fish will also be considered. Special attention is also given to current problems especially where there is an economic impact. Throughout the topic, issues of management and control will be discussed.