Solving parasite-related problems in cultured marine fish

Abstract

1. 1. Our knowledge of parasite born e diseases of cultured marine fish is restricted by the limited extent of practiced mariculture. 2. 2. Several parasites, pathogenic to fish including capsaloid, microcotylid and diclidophoran monogeneans and caligid copepods are ubiquitous in mariculture systems in diverse species of fish and geographical regions. 3. 3. The alga Amyloodinium ocellatum and the ciliated protozoan Cryptocaryon irritons are not as ubiquitous, but nevertheless present the most serious risk to farmed fish of most species due to their high pathogenicity, fecundity and resistance to conventional means of control. 4. 4. Infections in maricultured fish are dominated by monoxenous parasites. Occurence of heteroxenous parasites is restricted by their requirement for additional hosts to maintain transmission. 5. 5. Cage culture allows free exchange of infection between caged and native fishes; in inshore systems infections have to be introduced primarily from external sources. 6. 6. Water supply does not appear to be an efficient route of entry of infection into culture systems; parasites are introduced either by wild fry or wild breeders collected into the system, or with wild fish infiltrating via water supply or drainage. 7. 7. Adverse growth conditions are the most common circumstances in outbreak of epizooites. Over-crowding does not appear to promote primarily epizooites, its impact is indirect by contributing to the deterioration of the growth conditions. 8. 8. Epizooites are likely to occur also in juvenile, immunologically naive fish as well as following introduction of parasites into unexperienced fish population. 9. 9. Control has been implemented thus far through an empirical approach. Recent research is geared towards the development of methodology specifically designed to the needs of mariculture.