ENRICHMENT OF LIVE FOOD WITH ESSENTIAL FATTY-ACIDS AND VITAMIN-C - EFFECTS ON MILKFISH (CHANOS-CHANOS) LARVAL PERFORMANCE

The effects of essential fatty acids (EFA) and vitamin C-enriched live food on growth, survival, resistance to salinity stress and incidence of deformity in milkfish larvae reared in tanks were investigated. La rvae were either fed rotifers cultured on Chlorella sp. and newly hatc hed Artemia nauplii (control), highly unsaturated fatty acid (HUFA)-en riched rotifers and Artemia nauplii or HUFA + vitamin C-enriched rotif ers and Artemia nauplii. Milkfish growth in outdoor nursery ponds was also assessed to compare with growth in indoor tanks. Milkfish fed rot ifers/Artemia enriched with HUFA (32-48 mg dry weight, DW) or HUFA + v itamin C (33-45 mg DW) exhibited significantly (P < 0.05) higher growt h than those given unenriched live food (24-27 mg DW) after 40 days of culture. Growth of milkfish in nursery ponds (albeit lower in stockin g density) showed similar trends as those reared in tanks. When subjec ted to salinity stress (Day 25), mortality of the HUFA + vitamin C-tre ated fish and HUFA-treated fish were significantly lower (P < 0.05) th an the control fish. Survival of 26-day old milkfish, however, did not differ significantly (P> 0.05) among the treatment groups. Forty-day- old milkfish fed HUFA + vitamin C-enriched live food had significantly lower (P < 0.05) incidence of opercular deformity (mainly cleft branc hiostegal membrane) (8.4 -14.7%:) compared with those given HUFA-enric hed (15.8-23.5%) or unenriched(25.3-33.5%) I;ve food. Results demonstr ated the effect of HUFA enrichment in enhancing milkfish larval growth and resistance to salinity stress but not overall survival. Moreover, HUFA and ascorbate supplementation decreased but did not totally elim inate incidence of opercular deformity in milkfish larvae. (C) 1998 El sevier Science B.V. All rights reserved.