Evaluation of Teaseed Cake as a Piscicide for the Culture of Giant Freshwater Prawn, Macrobrachium Rosenbergii

Abstract

Results from acute toxicity tests indicated that teaseed cake is more toxic to silver barb (Puntius gonionotus) and marble goby (Oxyleotris marmorata) than to giant freshwater prawn. Giant freshwater prawn can tolerate up to 50.0 mg 1^-1 of teaseed cake without any mortality after 24 h, while concentrations of 18.0 and 28.0 mg 1^-1 of teaseed cake can completely eliminate silver barb and marble goby within 3 and 4 h, respectively. The 24-h LC₅₀ of teaseed cake on 0.05, 4.70 and 23.10 g prawn were 135.0, 62.0 and 61.0 mg 1^-1, respectively, while the 24-h LC₅₀ of teaseed cake on 0.45, 3.26 and 7.00 g silver barb were 2.8, 10.0 and 10.1 mg 1^-1, respectively. Meanwhile, the 24-h LC₅₀ of teaseed cake on 1.43 and 45.05 g marble goby were 16.0 and 22.0 mg 1^-1. Application of teaseed cake at the concentration of 30 mg 1^-1 after reducing water level to half the depth of water storage level and letting it stand for 6 h before refilling to normal level did not have any effect on growth and survival rate of giant freshwater prawn after a 4-week experimental period. Results from this study indicated that selective eradication of competitive and predatory fishes in giant freshwater prawn culture ponds can be done by lowering water level in the ponds to half the volume, applying 30 mg 1^-1 of teaseed cake, letting it stand for 6 h and then refilling the ponds.