Acute toxicity of the synthetic pyrethroid deltamethrin to fingerling European catfish, Silurus glanis L.

摘要

S. glanis fingerlings were exposed to various concentrations of deltamethrin (0.25, 0.50, 0.75, 1.0, 2.0, 3.0 and 4.0 micro g/litre). Mortality was evaluated at one, 24, 48, 72 and 96 h after the onset of exposure to deltamethrin. The toxicity of deltamethrin increased with the increase in its concentration and exposure duration. The LC50 values for one, 24, 48, 72 and 96 h were 2.497, 1.446, 1.215, 0.866 and 0.686 micro g/litre, respectively. Behavioural responses were observed in S. glanis at 1-12 h during the first day of exposure and every 12 h during the last 3 days of exposure. Specimens exposed to 0.0 and 0.25 micro g/litre exhibited normal behaviour, whereas those exposed to 0.50 micro g/litre showed normal behaviour during the first 48 h, but exhibited abnormal behaviour, such as reduced activity and loss of equilibrium, with longer exposure. Changes in behaviour were evident at 20 minutes after exposure to 0.75, 1.0, 2.0, 3.0 and 4.0 micro g deltamethrin/litre. The abnormal behavioural responses recorded for deltamethrin concentrations higher than 0.50 micro g/litre included the loss of equilibrium, rapid gill movement, erratic swimming, swimming on the water surface, gulping of air from the water surface, or staying motionless at the bottom of the aquarium..