Thesis (M.Sc.) - Asian Institute of Technology, 2000

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development

Thesis (M. Sc.) - Asian Institute of Technology, 2000

Although small-scale aquaculture in Cambodia has gradually developed, farmers received low fish yields, which had 62.43 kg/297 m2/7 months for trial farmers and 48.9 kg/310 m2/7 months for non-trial farmers. The extrapolated net fish yields were 3, 153 and 2,366 kg/ha/year for trial and non-trial farmers, respectively. It was hypothesized that one can improve fish production by optimize stocking ratio, feeding and fertilizer strategies. On station experimental trial, it was carried out to check the validity of the hypothesis growth rate of silver barb in polyculture (silver barb, tilapia and common carp) system at the Asian Institute of Technology. A 2 x 2 factorial experiments with two different stocking ratios ( 4. 5:4.5:1, silver barb: tilapia: common and 1. 5: 5: 3 . 5, silver barb: tilapia: common carp) at two feeding treatments (with or without supplementary feed) were used to evaluate fish growth and fish yields. Initial stocking sizes were 1.82, 0.16 and 0.4lg of silver barb, tilapia and common carp, respectively. Fish were stocked at a rate of 3 fish/m2 for a culture period of 90 days, in twelve earthen ponds with an area of 200 m2 . Water depth ranged from 0.7 - 0.8 m and was maintained during the experimental period. There were three replicates for each treatment. All ponds were fertilized with cow manure (50 kg/ha/day), green manure (25 kg/ha/day), urea (4 kg N/ha/day) and triple superphosphate (1 kg P/ha/day) at the same rate in each pond. Supplementary feeds were duckweed (3% of fish body weight on dry matter basic) and rice bran (3% of fish body weight). The net fish yields for 200 m2 for experimental ratio (4.5:4.5:1, silver barb: tilapia: common carp) with and without feeding and farmer ratio (1.5 :5:3.5, silver barb: tilapia: common carp) with and without feed were 40.62, 23.49, 39.61 and 29.83 kg/3 months, respectively. The correspondent extrapolated net yields of experimental ratio with and without feeding and farmer ratio with and without feeding were 8127, 4698, 7926 and 5964 kg/ha/year, respectively. The experimental ratio with feeding had higher gross margin (81, 73 4 Riels) than the rest of the treatments. The present experiment of both experimental ratio with feeding and farmer ratio with feeding provided the highest growth rate. The results showed that the feeding is more important feeder significantly affecting fish growth and yield than the stocking ratio of difference fish species.