The lsraeli Joumal of Aquaculture - Bamidgeh 50(3), 1998, 91-98
MASS PRODUCTION OF GREY MULLET, MUGIL CEPHALUS:
EFFECTS OF ENVIRONMENTAL AND NUTRITIONAL FACTORS
ON LARVAL PERFORMANCE
Moti Harel, Sachi Ben Atia, Vered ZIotkin and Amos Tandler
National Center for Mariculture, P.O. Box 1212. Eilat, Israel
(Received 28.12.97, Accepted 20.5.98)
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 supplementation of live microalgae (Nannochloropsis oculata or isochrysts galbana) to the rearing medium. The effects of tank size, initial egg density and water salinity on larval growth, survival and swim-bladder inflation were evaluated.
Larval survival, with no apparent effect on growth, improved significantly from 0.5±0.2% to 4.90±5% with the increase in tank volume from 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 significant (p>0.05), although a general increase in survival with reducing salinity was observed. While water salinity did not significantly affect (p>0.05) larval growth, the size distribution in the population differed with a higher proportion of large larvae at the higher salinity. Salinity had a significant 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.