Acute Toxicity of deltamethrin and permethrin and their Sublethal effects on Growth and Feeding in Anabas testudineus

The 24, 48, 72 and 96 h LC 50 values of the synthetic pyrethroid insecticides deltamethrin and permethrin for the climbing perch Anabas testudineus were 0.11, 0.09, 0.08, and 0.07 mg l -1 , and 2.07, 1.41, 1.02, and 0.93 mg l -1 , respectively. Although deltamethrin was more toxic than permethrin, the 24-96 h LC 50 pattern of the latter displayed a steeper slope that predicted increase in its toxicity on longer exposure. The fish was also exposed to sublethal concentrations of 1% and 10 % of the 96 h LC 50 of the two pesticides for 11 weeks. The sublethal exposure of the two pesticides affected food consumption significantly thereby resulting in inhibition of growth.