Effects of cowdung application on the production of mud crab (Scylla serrata Forskal) in brackishwater pond

A culture experiment of mud crab for 84 days was conducted in earthen pond at Brackishwater Station, Bangladesh Fisheries Research Institute, Paikgacha, Khulna. The aim of the experiment was to study the effects of cowdung application on crab production and water quality. There were three treatments as without cowdung (T1), 500 kg cowdung/ha/fortnight (T2) and 750 kg cowdung/ha/fortnight (T3) with three replicates for each. The result was evaluated on the basis of growth, production, survival rate etc. The experimental months were mid-April '96 to mid-July '96. To maintain a good water quality, water was exchanged in every spring tide. The range of salinity during the experiment was 8-19 ppt. Trash fish and fresh shrimp head were used as feed on raw basis in every alternate week at a rate of 8% body weight of crab at the same time rice bran and wheat flour were used at a rate of 2% body weight as a source of carbohydrate. The production of T1, T2 and T3, were 720.35 kg, 862.16 kg and 669.19 kg/ha respectively. Though the effects of cowdung on production of crab is insignificant but in terms of production, survival rate and growth, the study suggest that the application of cowdung in addition to feed can be recommended for mud crab culture at a rate of 500 kg/ha/fortnight.

Production of Thai sharpunti (Puntius gonionotus Bleeker) in polyculture with carps using low-cost feed

The effectiveness of duckweed and rice bran as a low cost supplementary feed was compared through a six months production trial of rajpunti (Barbodes gonionotus) with carps. Six earthen ponds of 360 m² each were used for the trial. Three ponds received duckweed, while the other three received rice bran as supplementary feed. Fish biomass after six months of rearing increased to an average of 2,056 kg/ha in ponds which received duckweed and 2,056 kg/ha in rice bran treated ponds. The net profit with duckweed and rice bran worked out to Tk. 69.752 and Tk. 73.480 kg/ha, respectively. This study revealed that duckweed is a low cost supplementary feed, particularly for farmers with limited income.