Abstract:

In Artemia franciscana, enriched for 24 h with emulsified lipids, the fatty acid DNA (22:6 omega 3) is unstable. In rotifers the level of DNA can be stabilised by adding algae rich in DHA to the fish tanks. To test this method for A. franciscana, enriched A. franciscana was incubated with the alga Isochrysis galbana, which is rich in lipids and DHA, at six concentrations ranging from 1 to 20 mg C/l at 13-14 degrees C. After lipid enrichment, A. franciscana contained 15% lipids of which 79% (116 mg g DW-1) were fatty acids. Of the fatty acids, 17% was DHA (19.8 mg g DW-1). After 72 hours incubation with I. galbana, the level of DHA decreased to 1.6-3.2 mg g DW-1, which was a reduction by 84-92%. This was independent of the algal concentration. The amount of total fatty acids decreased to 53-73 mg g DW-1, a reduction by 37-54%, independent of the algal concentration. The rates of loss of the fatty acids, and especially DHA, was greater during the first 24 h at the highest algal concentrations (8, 10 and 20 mg C/l). Enriched A. franciscana should therefore not be incubated with high algal concentrations (>6 mg C/l) during first feeding of marine fish larvae.
(SINTEF, Ctr. Aquaculture, Appl. Chem, N-7034 Trondheim, Norway)
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