Use of the brine shrimp, Artemia spp., in marine fish larviculture

Abstract

Since no artificial feed formulation is yet available to completely substitute for Artemia, feeding live prey to young fish larvae still remains essential in commercial hatchery operations. The nutritional quality of commercially available Artemia strains being relatively poor in eicosapentaenoic acid (EPA, 20:5 n-3) and especially docosahexaenoic acid (DHA, 22:6 n-3), it is essential and common practice to enrich these live prey with emulsions of marine oils. In Artemia, the most commonly applied boosting technique is a 24-h enrichment period after hatching. However, the variability of enrichment studied in one Artemia strain (Great Salt Lake, Utah, USA) by the ICES Working Group on Mass Rearing of Juvenile Fish, showed a high variability in fatty acid bioaccumulation under laboratory or commercial conditions. To avoid the variation originating from differences in commercial preparations, standardized ICES emulsions with different HUFA and DHA/EPA ratios have been formulated and are available for research purposes. It should be emphasized, however, that the enrichment technique has limitations as Artemia are selectively catabolizing some of the nutrients such as DHA and phospholipids. Research on the kinetics of DHA catabolism in various Artemia strains has shown that DHA catabolism is strain-dependent and could partially be overcome by the use of strains of different geographical origin. Nowadays, various enrichment emulsions have been formulated differing in the fatty acid composition of their triglycerides. In this respect, the traditional formulations rich in EPA have been replaced by new products rich in DHA and arachidonic acid. To reduce the risks for oxidation of these fatty acids, higher concentrations of vitamin E are incorporated into the emulsions. Also, vitamin C has been incorporated in booster formulations that increase the level of ascorbic acid in Artemia to 2000 ppm. All these changes in the formulation of the enrichment diets offer more possibilities to cover the needs of different species and help to reduce problems related to diseases, stress resistance, malformation, and pigmentation in numerous fish species. Although continuous disinfection of Artemia during hatching and enrichment is becoming a routine operation in many hatcheries, the interference of bacteria in hatching and enrichment remains an important study object for which probionts might also give some solutions. As more attention is given to the use of on-grown Artemia as a cheaper alternative to the use of nauplii, simple cost-effective production techniques have been developed. The use of the right size of on-grown Artemia for feeding ensures a better energy balance in food intake and assimilation, thereby improving the performance of the fish. Furthermore, its palatability induces a good and fast feeding response. These characteristics, coupled with the use of bioencapsulation techniques to enhance the quality of the on-grown Artemia, make this organism an optimum diet for nursery of the fish.