A study on the acute toxicity of pyrethroid deltamethrin on the fry rainbow trout (Oncorhynchus mykiss Walbaum, 1792)

Deltamethrin, a synthetic pyrethroid pesticide contaminating aquatic ecosystems as a toxic pollutant, was investigated in the present study for acute toxicity on fry of rainbow trout, Oncorhynchus mykiss. Deltamethrin was applied at concentrations of 0.25, 0.5, 1, 2, 4, 6, 8, 10, 12, 25, 50 μg L−1. The experiments were repeated five times and a total of 1200 fry rainbow trout was used. The water temperature in the experimental units was kept at 14 ± 1 °C. The number of dead fry rainbow trout significantly increased in response to increased deltamethrin concentrations between 0.50 and 12 μg L−1 (p < 0.05). With increasing deltamethrin concentrations, the fry fish exposed duration 1-96 h significantly increased the number of dead fry fish (p < 0.05 for each cases). The 1, 12, 24, 48, 72, and 96-h LC50 values (95% confidence limit) for fry rainbow trout were estimated to be 15.8708 (10.8550-24.2067), 7.0014 (4.3854-11.5177), 3.1856 (1.8438-5.1897), 1.6568 (0.7287-3.1600), 0.9800 (0.3060-1.8760), and 0.6961 (0.3184-1.6575), respectively. The LT50 time at deltamethrin concentrations of 0.25-50 μg L−1 (p < 0.05) were estimated to be 212h55m (138h26m-1485h47m)-1h33m, respectively.