Development of hatchery technology for the silver pomfret Pampus argenteus(Euphrasen): effect of microalgal species on larval survival

摘要

The silver pomfret Pampus argenteus (Euphrasen) is a new candidate for aquaculture and there is not much information available on its larval rearing. Investigations carried out using microalgae alone in the culture system for the initial feeding of the silver pomfret larvae showed that Chlorella, Isochrysis and Nannochloropsis without rotifers are not conducive to the survival of newly hatched larvae. At 6 days after hatching (DAH), a maximum survival of 3% (1.8 +/-1.69%) was observed with Isochrysis followed by Nannochloropsis (0.35 +/-0.21%) and Chlorella (0.25 +/-0.21%). All control larvae died at 6 DAH without microalgae. Further investigations using the above microalgae with rotifers and a mixture of these same microalgae with rotifers showed that significantly higher (P<0.05) survival could be achieved in the mixture of microalgae with rotifers in the culture system. At 12 DAH, the larval survival was 9.73lus/minus>1.39% in mixed species of algae compared with that of Isochrysis (6.93 +/-1.86%), Nannochloropsis (6.83 +/-0.61%), Chlorella (5.93 +/-2.76%) and seawater without microalgae or the control (0.73 +/-0.31%). The first incidence of feeding on rotifers at 4 DAH was significantly higher (P<0.05) in all treatments with microalgae than that of the control. The incidence of feeding in mixed species of algae at 4 DAH (60.0lus/minus>0.00%) and in Isochrysis (55.0 +/- 35.36%) was significantly higher (P<0.05) than that of Chlorella (40.0lus/minus>0.00%) and the control (25.0 +/-7.07%). Prey consumption of individual larvae increased significantly (P<0.01) at 8 DAH compared with that at 4 DAH. During this period, predation on rotifers by larvae was significantly higher (P<0.05) in mixed species of algae (12.85 +/-5.73 rotifers larva(-1)) than that of the control (6.75 +/-1.20 rotifers larva(-1)). The fatty acid composition of rotifers used during this investigation shows that significantly higher (P<0.05) 3 HUFA was present in rotifers treated with mixed algae plus commercial enrichment media 'Super Selco' and 'DHA Protein Selco'. Rearing of silver pomfret larvae up to the juvenile stage using mixed species of microalgae in the hatchery has been discussed. During 38 days of the larval rearing period, it was possible to achieve 3.6-4.2% larval survival with a mean of 3.9 +/-0.42%, which was considerably higher than in previous attempts (survival up to 1.5%).