Minimizing the use of fish oil enrichment in live feed by use of a self-enriching calanoid copepod Pseudodiaptomus annandalei

Unlike some harpacticoid and cyclopoid copepods, calanoid copepods are considered unable to enhance their highly unsaturated fatty acid (HUFA) profile in sufficient quantities if at all. This study demonstrates the capability of significant HUFA enhancements in the calanoid Pseudodiaptomus annandalei when cultured on Tetraselmis chuii, a relatively HUFA poor microalgae. A 48 h growth trial using newly spawned nauplii revealed adequate daily specific growth (0.31 +/- 0.06 d(-1)) when fed T. chuii. Another seven day trial was conducted where nauplii were cultured to adult stage while fed T. chuii. Fatty acids profiles were analysed in P. annandalei adults and next generation nauplii, which were then compared to the fatty acid profile in algal feed. Abundances of C20:2n-6, C20:3n-3 and C22:6n-3 were observed in the copepods but never in the algal feed. Copepod C22:6n-3 contents were 4-8 mg g(-1) dry weight, which is comparable to what has been observed in traditional live feeds. As P. annandalei tend to dominate habitats with changing food quality, the food environment may act as a selective force on the organism's ability to enhance its HUFA profile, irrespective of taxonomic order. Hence P. annandalei demonstrates good potential as nutritious live feed in extensive aquaculture.