METHODS FOR THE TAURINE ENRICHMENT OF LIVE PREY AND THEIR IMPACTS ON MARINE FISH LARVAE.

Matt Hawkyard*, Ben Laurel, Yoav Barr, Kevin Stuart, Mark Drawbridge and Chris Langdon
 
*Coastal Oregon Marine Experiment Station
and Department of Fisheries and Wildlife
Oregon State University
Newport, OR 97365
Matt.hawkyard@lifetime.oregonstate.edu

Marine fish larvae fed rotifers and Artemia have been shown to grow, survive and develop at slower rates when compared to those fed copepods. Taurine is highly concentrated in copepods (5-15 g kg-1) while present at lower concentrations in unenriched Artemia (~7 g kg-1) and rotifers (0-0.1 g kg-1). There is increasing evidence suggesting that taurine is an essential nutrient for many marine fish species and that taurine concentrations of cultured live prey may be growth-limiting for marine fish larvae. Consequently, cultured live prey may require taurine enrichment to meet the needs of marine fish larvae. Low molecular weight water-soluble (LMWS) nutrients, such as taurine, are difficult to deliver to marine organisms because these substances may be rapidly lost during enrichment and feeding processes. Alternatively, LMWS nutrients may be dissolved in the water of the live prey during culture or enrichment; hereafter referred to as the dissolved enrichment method. There are several drawbacks associated with dissolved enrichment methods including: 1) nutrient wastage, 2) loss of labile compounds, 3) bacterial growth, and 4) other impacts on water-quality (i.e. changes in pH).

We investigated the use of synthetic microparticles, wax spray beads and liposomes, for the enrichment of rotifers and Artemia with taurine and compared microparticulate enrichment techniques with dissolved methods. We found that taurine concentrations similar to those measured in copepods could be achieved in rotifers and Artemia using microparticulate and dissolved enrichment techniques. However, microparticulate methods resulted in 60 to 80 fold reductions in taurine usage when compared to dissolved enrichment methods. Larval growth trials provided evidence that taurine enriched live prey promoted growth, survival and development of marine fish larvae, however, these effects varied among enrichment methods. These techniques have direct use in larval fish nutrition research and may have applications in commercial hatcheries.