| Abstract | Semi-intensive freshwater fish culture in Indonesia has developed rapidly, but its production is low. One of the efforts to improve fish production is to develop feeding strategies. To attain this goal, a series of field experiments was carried out at the Asian Institute of Technology, Bangkok, Thailand using silver barb (Pumius gonionotus). Feasibility study dealing with silver barb culture in Sumatra, Indonesia was also discussed. Experiment 1 was aimed at evaluating fertilization regimes and the value of supplementary feed for fish that have access and have no access to pond bottom. Fish were raised in floating and sinking cages at a density of 2 fish/m2 or 36 fish/cage with and without feeding supplementary feed containing 25% protein and 4.3 kcal gross energy at ad libitum for 56 days. The cages were placed in ponds fertilized at different rates (1.0 kg nitrogen, N + 0.5 kg phOSphOI’OUS, P/kg/ha against 3.0 kg N + 1.5 kg P/kg/ha). The results showed that growth and yield of silver barb significantly increased with increasing fertilization rates. Feeding significantly increased fish growth and yield. Apparent feed conversion ratio (FCR) was low in high fertilized ponds. However, there was no effect of cage position. Therefore it can be concluded silver barb can be raised in high fertilized ponds with supplementary feed. It was not necessary for silver barb to access pond bottom to obtain the nutrient for their growth Supplementation of dietary protein, vitamin and mineral on diet for silver barb in high fertilized ponds was evaluated in Experiment 2. Stunted fish were raised in floating cages at a density of 2/m2 or 36/cage and fed seven is caloric feeds at ad libitum twice a day for 56 days. Four feeds contained 15, 22.5, 30.0 and 37.5 protein respectively. The rest of the feeds containing 30% protein varied in vitamin and mineral supplementation: added with vitamin and mineral, with vitamin only, with mineral only, or without both materials. The highest growth and lowest apparent FCR of fish were observed for dietary protein level above 30%. Dietary protein between 22.5 to 30.0% resulted in similar protein utilization. Effect of supplementing vitamin and mineral on diet was not significant. Therefore, this experiment showed that required dietary protein level for silver barb in high fertilized pond ranged from 22.5 to 30.0%. Commercial vitamin and mineral were not required in feed formulation. Experiment 3 was conducted to revise Experiment 2. The treatments were dietary protein levels (20%,25%,30%) and vitamin levels (0%,1%,2%). Silver barb were raised in cages in high fertilized ponds at a rate of 2/m2 or 36/cage and fed dietary treatments for 30 days. Effect of protein levels on growth of silver barb was significance. The growth at 25 and 30% protein was comparable and higher than those in 20% protein feed. The best apparent FCR was 1.25 at 25—30% dietary protein levels. The growth was comparable for fish fed on dietary vitamin level of 0 and 1%. This was also observed for 1 and 2% dietary vitamin levels. However effect of vitamin level was not apparent for fish yield and FCR. Hence, it was concluded that diet for silver barb in high fertilized ponds should be formulated to contain 25% protein without supplementing commercial vitamin. Experiment 4 was carried out to determine the effect of feed intake of different sizes of silver barb in fertilized pond. Fish were raised in cages in high fertilized ponds at a rate of 18 fish/one m2 cage and fed a diet containing 25% protein at ad libi’tum for three months. The growth rate of silver barb decreased exponentially with increasing fish size. This was also observed for relative feed intake. Apparent FCR linearly increased with increasing fish size. Observed growth, relative feed intake and apparent FCR within the first month and three month of fish culture showed a similar pattern. This study, therefore, indicated that daily feeding allowance for silver barb in high fertilized ponds could be adjusted accordingly with increasing fish size, namely: 10-<25g= 4.0% of fish weight, 25-<50g= 4.3%, 50- <100g= 2.7%, 100-<150g= 2.5%, 150-<200g= 2.1% and >200g= 1.7%. The effect of stocking density on nutrient requirement of silver barb was evaluated in Experiment 5. Fish were raised in cages in high fertilized ponds at different rate of 0.5, l, 2, 3, 4, and 5/m2 respectively. Diet containing 25 % protein was given to the fish for 92 days. Daily feeding allowance of fish was adjusted after fish sampling. Survival rate of silver barb was as high as 90% and comparable for each cage. Growth of fish linearly decreased with increasing stocking rate. Yield increased with increasing stocking rate. Apparent FCR slightly increased with increasing biomass, ranging from 1.1 to 1.2 for low and high stocking rate. This experiment showed that fish density of 4 fish/m2 was desirable for silver barb cultured in high fertilized pond. From the results of the experiments, it can be concluded that (1) silver barb can be raised quite well in a pond fertilized with urea and TSP at a respective rate of 3.0 kg N and 1.5 kg P/ha/day and 10 kg dry chicken manure/ha/day. (2) Fish should be fed on diet containing 25% protein and 4.3 kcal gross energy formulated using locally available feedstuffs of fish meal, soybean meal, rice bran, corn oil, fish oil. (3) It was not necessary to add commercial vitamin and mineral premix in diet formulation. (4) Stocking density of 4 fish/m2 produced the best growth rate (2.76 %/day), the highest yield (5.4gi’m fday) and the lowest apparent FCR (1.2) of silver barb. A desk study concerning silver barb pond farming to meet local demand was carried out using small scale farmers in Sumatra, Indonesia as the target. Field experiment (Experiment 1 and 5) and secondary data was used in this study. The duration of the project was five years, following the 5 Year Plan of Government of Indonesia. Economic and financial analysis showed that combination of high fertilization and supplementary feed in silver barb culture was profitable in the short and long run. Stocking density suggested ranged from 4-5 fish/m2. Wide range fluctuation of market fish price as well as feed may not influence silver barb farming. It was concluded that the proposed system of silver barb culture deve10ped in this study can be used to develop small scale silver barb farming in Sumatra, Indonesia. |