A Preliminary Study on Rearing of Juvenil Macrobracium rosebergii in Ditch

Abstract

Three ditches designated as KU-1, KU-2 and KU-3 at Kasetsart University, Bangkhen were used for rearing the juvenilesof Macrobrachim rosenbergii.Area of KU-1, KU-2 and KU-3 were 50, 50 and 100 sq. meters, respectively.Before stocking, the ditches were drained, the mud was taken out and predatory fish were eradicated with derris root at 2 kg. per 100 sq. meter of the ditch area. The ditches were fertilized with NPK ratio of 1-2-0 at 2 kg. per rai per month. Pond weed, Ipomea was also placed in the ditches for shelter and food for the stocked at 5 prawns per one sq. Meter of the ditch area. Prawns were fed with chopped snail flesh, Pila spp. As supplemental food thrice a week. Ditches were drained on December 25, 1970 for determining growth and survivals. The second drining was on June 8, 1970. But no prawn were presented on the draining. Possibly, the depletion of dissolved oxygen in ditchrs in ditches caused the death of the prawns. Results of the first draining showed that prawns that were reared in KU-l ditch attained a bigger size, and yieded a higher production than those in KU-2 and KU-3. The number of remaining in KU-1 was less than those in KU-2 and KU-3, KU-2 also produced a better growth and higher production than those in KU-3. The differences were possibly due to competition for food between stocked prawns and the undesirable Kung foi (Macrobrachium lanchesteri ) predatory Plachons as well as the fertility of the ditches before stocking because these ditches had been used for growing crops for at least 20 years.