Disease prevention and control for gametes and embryos of fish and marine shrimp

Abstract

Disease prevention is a facet of the total quality management for gametes and embryos of fish and marine shrimp. Gamete health is strongly influenced by broodstock health and nutrition, the quality of the techniques used during gamete production, collection, storage and pre- to post-hatch conditions in embryo incubation. Poor quality gametes or unhealthy conditions during collection and incubation can result in embryo mortality and/or lead to the attack of the eggs by saprophytic bacteria and fungi. Gametes and embryos may also provide the means for vertical transmission of certain pathogens from brood animals to their offspring. There are a number of viruses of fish and shrimp which may transfer from broodstock to the offspring at the time of spawning. A few bacterial and fungal pathogens are also dispersed in this way. For the vertically transmitted biotic agents, the principal biological impact of the disease occurs typically well beyond egg hatching. Specific viruses, bacteria and fungi are the major infectious agents of concern for the gametes and embryos of fish and marine shrimp. Prevention of the diseases that stem from these agents involves primarily the application of the best management practices (BMPs) available for broodstock selection and maturation; gamete production, collection and storage; and pre- to post-hatch egg incubation. Specific techniques have been developed for the control of selected pathogens of high economic significance to fish and penaeid shrimp culture. Incomplete knowledge regarding BMPs that are unattainable because of system or other constraints and human error are important factors hindering the prevention of egg transmitted infectious diseases of the mass cultured fish and shrimp species. Using specific pathogens as examples, like a number of the measures applied by aquaculturists to eliminate or reduce the pathogen/disease risks associated with gametes and embryos of fish and marine shrimp, are discussed here. The tactics highlighted are the application of BMPs to maintain gamete and embryo health; the use of specific pathogen-free (SPF) broodstock; the testing and elimination of broodstock carriers of specific pathogens; chemical treatment of the broodstock to control a specific pathogen; the use of pathogen-free culture water; chemical and/or physical disinfection of the culture water; chemical treatment of the gametes, the embryos or the early life stages; and mechanical rinsing with pathogen-free water of the eggs or the early larval stages.