Principal investigator: Dr. Md. Akhtar Hossain, Assistant Professor

Project site: Meherchandi Village, Motihar, Rajshahi, Bangladesh.
Collaboration: Rajshahi University and BFRF (Bangladesh Fisheries Research Forum)
Project duration: 2006-2007

Status: Completed

Executive Summary

The effect of stocking density of prawn in surface feeding carps cum prawn polyculture was studied for a period of six months from September, 2006 to February, 2007 in ponds of 0.1 ha in Northern Bangladesh under 4 treatments each with 3 replications. The stocking density of surface feeding carps was the same (silver carp 12 + catla 8/decimal) in all the treatments while that of prawn was 20, 40, 60 and 80/decimal in treatments T1, T2, T3 and T4, respectively.  The initial average weight of prawn, silver carp and catla was 2.39 ±0.10 g, 49.17 ±6.59 g and 50.10 ±1.09 g, respectively. Ponds belonging to all the treatments were subjected to the same fertilization (cowdung-200g/decimal + urea-5g/decimal + TSP - 5g/decimal/day) and feeding (rice bran-50% + fishmeal-20% + mustard oil cake-30% twice daily at a rate of 5% of the prawn body weight regime). Water quality parameters were monitored fortnightly and significant variation was found in the parameters like temperature, transparency, pH, dissolved oxygen, ammonia nitrogen, alkalinity, phytoplankton concentration and zooplankton concentration while treatment to treatment variation was significant in case of alkalinity, pH and transparency but that of dissolved oxygen, ammonia nitrogen, temperature, phytoplankton concentration and zooplankton concentration was not significant. The variation of average weight gain and final weight was found to be significant (P<0.01) by the treatments and but that of average SGR, survival rate and yield was not significant irrespective of species and months. Species and month based variations were found to be significant (P<0.01) for all the growth parameters. In case of total yield (2721-2918 kg/ha) treatment to treatment variation was not significant. The combined effect of species and treatment was found to be significant (P<0.01) on the mean values of yield where the contributions of prawn and carp were found to be 14.74% (T1) – 37.87% (T4) and 62.17% (T4) – 85.26% (T1), respectively. The study indicates that comparatively higher production of the valuable species like freshwater prawn can be obtained with more or less satisfactory production of surface feeder carps by treatment T4. The present investigation was done in the cooler months, it is felt necessary to study the growth of prawn in warmer season as well as to explore the feasibility of prawn nursery and to find out the cost benefit analysis of the prawn based surface feeding carp polyculture system in Northern Bangladesh.