THE USE OF SILAGES PREPARED FROM FISH NEURAL TISSUES AS ENRICHERS FORROTIFERS (BRACHIONUS-PLICATILIS) AND ARTEMIA IN THE NUTRITION OF LARVAL MARINE FISH

Marine fish larvae have a requirement for large quantities of n-3 high ly unsaturated fatty acids (HUFA), particularly docosahexaenoic acid ( DHA; 22:6n-3), and dietary deficiencies of these induce a range of pat hologies in fish including behavioural abnormalities. Therefore, there is a growing demand for natural lipids highly enriched in DHA as nutr itional supplements during larval development. In the present study, D HA-rich products were obtained from fish neural tissues by a procedure involving ensiling in organic acids followed by neutralisation, dryin g, milling and sieving to produce the final particulate, crumbed produ cts. Lipid content varied in the neural tissue silages from 5.5% to 46 .5% but all lipid contained high percentages of DHA and high DHA:EPA ( eicosapentaenoic acid; 20:5n-3) ratios ranging from 3.5 to 5.4. Tuna e ye silage was a high lipid, high triacylglycerol (90.6% of total lipid ) product and was particularly effective in increasing DHA content, ou tperforming a commercial product, in rotifer ( Brachionus plicatilis) enrichment. Cod brain/eye silage had an intermediate content (18.2%) o f lipid, which contained almost 50% as phospholipid, and proved as eff ective as a commercial enricher in increasing DHA content in Artemia n auplii, Moreover, Artemia nauplii, enriched with the cod brain/eye sil age were more effective than nauplii enriched with a commercial enrich er in increasing the DHA content of larval turbot brain. In conclusion , tuna eye and cod brain/eye silages are useful as enrichers of Artemi a nauplii and rotifers for feeding marine fish larvae prior to weaning onto pelleted formulated diets.