ACIAR Project FIS/97/73 - Library - Network of Aquaculture Centres ...

Research into the optimal protein requirement of humpback grouper C. altivelis hasbeen conducted at RSCF Gondol and at RICF Maros. At RSCF Gondol, theexperiment on dietary protein requirement was conducted in 15 polycarbonate tanks,each 30 litres in volume. All tanks were equipped with flow-through water system.Hatchery produced juveniles of 5.5 ± 0.2 g in body weight were randomly selectedand 10 fish stocked in each tank. Fish fed experimental diets containing differentlevels of protein, i.e., 36, 42, 48, 54, and 60% for 50 days. The experiment wasdesigned using CRD with three replicates for each treatment. Broken line analysis ofbody weight gain data showed that optimum dietary protein requirement formaximum growth of juvenile humpback grouper was 54.2 %. Details of thisexperimental work are appended (Appendix 3).At RICF Maros, these experiments were carried out at the floating net cage site atBarru. Diets were formulated to provide crude protein contents ranging between 30and 55% at 5% increments. Juvenile C. altivelis sourced from RSCF Gondol wereselected on weight uniformity and assigned randomly into 18 of 1×1×1.2 m net cagesat a stocking density of 15 fish/cage. The mean weight (± SD) of the fish was 17.3 ±2.10 g. Fish were fed twice daily at 0800 and 1600 h.Growth rate and food conversion ratio improved curvilinearly with increasing dietaryprotein content. Survival rate was not significantly different over the dietary range.Broken line analysis of the growth rate data detected a break point at a dietary proteincontent of 45.3%, suggesting that this level appears to be the optimal for maximisinggrowth rate of C. altivelis. Full details of this experiment are appended (Appendix 3).3.3.2 Fatty acidsExperimental work at Gondol has investigated the n-3 HUFA requirements ofC. altivelis, with the objective of identifying the minimum dietary requirement toprevent n-3 HUFA deficiency. The results indicated that growth of C. altivelis wassignificantly affected by the level of n-3 HUFA in diets. Fish fed diet without n-3HUFA supplementation had significantly lower growth than those fish fed diets withn-3 HUFA level of 1.0% – 3.0%. Growth of fish that were fed diets with levels of n-3HUFA 1.0%, 1,5%, 2.0% and 3.0% were not significantly different (P>0.05). Thisexperiment shows that the minimum dietary n-3 HUFA requirement for growth ofhumpback grouper juveniles is 1.0%. Details of this experimental work are appended(Appendix 3).3.3.3 PhospholipidsThis component has not yet commenced. Based on the results of the inter-laboratorycalibration exercise, which demonstrated substantial differences between laboratoriesfor phospholipid analyses, some additional cross-checking of phospholipid analyseswill be necessary.3.4 Fishmeal replacementA series of eight experimental diets was tested at SEAFDEC to determine the effectsof replacement of fish meal with meat solubles at proportions ranging from 0 to100%. Generally, weight gain and SGR tended to decrease as the percent replacementof fish meal with processed meat solubles increased. The fish-meal-based control dietgave significantly better growth than diets with 60% to 100% replacement. Thosefish given diets with 100% meat solubles, 0% fish-meal exhibited the lowest growthrate compared to the rest of the dietary treatments.ACIAR Project FIS/97/73 – Annual Report – June 2000 17