Mass production of grey mullet, Mugil cephalus: Effects of environmental and nutritional factors on larval performance

Grey mullet, Mugil cephalus, larvae were raised 43 days after hatching in a commercial large-scale system. HUFA (n-3) enriched Brachionous plicatilis rotifers were used as the first feed in conjunction with continuous supplem entation of live microalgae (Nannochloropsis oculata or Isochrysis galbana) to the rearing medium. The effects of tank size, initial egg density and w ater salinity on larval growth, survival and swim-bladder inflation were ev aluated. Larval survival, with no apparent effect on growth, improved signi ficantly from 0.5+/-0.2% to 4.9+/-0.5% with the increase in tank volume fro m 400 to 1800 l. No significant increase in final larval yield was observed with the increase in initial egg density from 50 to 200 viable eggs/l. The effect of water salinity (25-40 ppt) on larval survival was not significan t (p>0.05), although a general increase in survival with reducing salinity was observed. While water salinity did not significantly affect (p>0.05) la rval growth, the size distribution in the population differed with a higher proportion of large larvae at the higher salinity. Salinity had a signific ant effect on larval swim-bladder inflation on day 11 posthatch; 98+/-3% of the larvae had an inflated swim bladder at 25 ppt as compared to 53+/-16% at 40 ppt. Phytoplankton supplementation to the rearing medium was found to be essential for larval survival.