Optimization of feeding frequency of Asian seabass ( Lates calcarifer) fry reared in net cages under brackishwater environment

Abstract

An experiment was conducted in brackishwater environment to determine the optimal feeding frequency for growth, effective feed conversion, survival, shooters emergence and size variation in Asian seabass fry reared in the net cages. Four feeding frequencies of one (T1), two (T2), three (T3) and four (T4) times a day were evaluated as treatments in triplicate for a period of 5 weeks. Hatchery produced weaned seabass fry (25.9 ± 0.3 mm/203.8 ± 4.6 mg size) stocked at 120 numbers per cage were fed with a commercial marine fish larval diet containing 55% crude protein at 10% of the biomass daily for the first 3 weeks, followed by 8% for the remaining 2 weeks. Although, the highest growth was recorded in T3, the final length (45.9 ± 0.3 mm) and weight (1203.8 ± 4.6 mg) did not differ significantly ( P > 0.05) from that of T4. Whereas, fish with one or two times feeding exhibited significantly lower growth ( P < 0.05). Daily weight gain, percentage weight gain and specific growth rate were significantly higher in T3 ( P < 0.05), while there was no significant variation ( P > 0.05) between T3 and T4. Significantly higher survival of 75.89 ± 4.17% was recorded in T3 than those of one and two times fed fish ( P < 0.05). The fish in T3 had significantly improved feed conversion ratio ( P < 0.05). No significant differences were recorded among treatments for the cumulative number of shooters separated and coefficient of variation in the harvest weight, which were ranging from 9.67 to 12.00 and 0.113 to 0.124, respectively. This study infers that the Asian seabass fry can achieve maximum growth, survival and better feed conversion when they are fed a given ration with three times feeding daily in brackishwater net cage rearing. The findings also have practical significance towards establishing Asian seabass seed rearing package and will directly benefit the nursery operators.