Parasitic diseases in marine cage culture--an example of experimental evolution of parasites?

Rapid development of fish culture in marine cages has been associated with an emergence of parasitic diseases. There is a general trend to an increase in infections with ectoparasites with direct life cycles and a reduced diversity of parasites in aquaculture. Some mariculture creates conditions that are similar to serial passage experiments, which are used to study adaptation during experimental evolution of pathogens. In particular, increased density of fish, repeated introduction of naive hosts, homogenous host populations, fast growth and a potential decrease in genetic diversity are attributes of both aquaculture and serial passage experiments. Some free-living organisms, for example Neoparamoeba spp. and Uronema spp. parasitise fish in culture, but have not been reported from wild populations. Farming fish in marine cages can increase the risk of outbreaks of parasitic diseases, including those caused by opportunistic parasites. However, aquaculture has the potential to control parasitic diseases through selective breeding, vaccination and general fish health management.