The potential of increasing pond fish production by growing dhaincha (Sesbania rostrata) in the pond bottom

An on-farm trial was carried out in 12 earthen ponds at the Montala Village, Muktagacha, Mymensingh for a period of 4 months (July-October 2003) to assess the potential of increasing pond fish production by growing dhaincha (Sesbania rostrata) in the pond bottom. The experiment consisted of four treatments each with three replications with an object of replacement for the use of fertilizers in fish production. In treatment-I (T sub(1)) dhaincha without fertilizer, in treatment-II (T sub(2)) dhaincha with 25% fertilizer, in treatment-III dhaincha with 50% fertilizer and in treatment-IV (T sub(4)) dhaincha with 100% fertilizer were used. Dhaincha seed was sown at 100 g times 40m super(-2) from bottom to dike. After 50 days of sowing dhaincha on the moist pond bottom, lime and fertilizer were used and fish fry were released after watering the ponds. The stocking density of rohu (Labeo rohita), catla (Catla catla), mrigal (Cirrhinus cirrhihosus), silver carp (Hypophthalmichthys molitrix) and Thai sarputi (Puntius gonionotus) was 12,350 fish times ha super(-1) in all treatments. Fertilization was done at 100 g urea + 100 g TSP times 40 m super(-2), 50 g urea + 50 g TSP times 40 m super(-2), 25 g urea + 25 g TSP times 40 m super(-2) in treatments T sub(4), T sub(3) and T sub(2), respectively and no fertilization in T sub(1). Some of the water quality parameters showed significant difference among different treatments, but most parameters were found within the suitable ranges for pond fish culture. Recorded periphyton groups were composed of Bacillariophyceae (9), Chlorophyceae (10), Euglenophyceae (2), Cyanophyceae (6), Crustacea (2) and Rotifera (3). Among these groups Cyanophyceae was the most abundant in number of which Microcystis was most abundant. The mean abundance of Cyanophyceae in treatments T sub(1), T sub(2), T sub(3) and T sub(4) were 62,099 plus or minus 7,159 cells times cm super(-2), 59,259 plus or minus 7,941 cells times cm super(-2), 53,827 plus or minus 12,983 cells times cm super(-2) and 56,419 plus or minus 13,015 cells times cm super(-2), respectively. The mean survival rate in treatments T sub(1), T sub(2), T sub(3) and T sub(4) were 82.14, 84.53, 82.83 and 83.23%, respectively. The highest growth rate of fish observed after one month of stocking and then growth rate was decreased gradually. Highest total net fish yield was recorded in T sub(2) (1,619 kg times ha super(-1)), where 25% fertilizer was used along with Dhaincha followed by T s