Susceptibility of Fluvalinate and Esfenvalerate on Adult Tarek Alburnus tarichi (Güldenstädt 1814)

Fluvalinate and esfenvalerate are pyrethroid insecticides and are used to control insect pests. These pesticides can enter the aquatic environment in different ways after use, causing toxicity. Tarek is a fish of the Cyprinidae family native to the Lake Van basin in Turkey. This study was conducted to determine the acute toxicity of fluvalinate and esfenvalerate to adult tarek. In the bioassays, tarek with an average length of 20.6±1.2 cm and an average weight of 93.9±14.0 g were used for fluvalinate, while an average length of 19.7±1.2 cm and an average weight of 85.5±16.6 g were used for esfenvalerate. Fish were exposed to fluvalinate using the semi-static test method, and esfenvalerate using the static test method. The toxicity tests were performed under the natural photoperiod. The concentrations used for fluvalinate were 0.15, 0.30, 0.45, 0.60 µg L⁻¹, while for esfenvalerate they were 0.33, 0.67, 1.00, 1.34 µg L⁻¹. The tests were performed at 13±1 °C for 96 hours with dechlorinated tap water. At the end of the toxicity tests, the mean lethal concentration (LC₅₀) of fluvalinate after 96 hours was determined to be 0.338 (0.230-0.477) µg L⁻¹ and the above concentration of esfenvalerate was determined to be 0.475 (0.293-0.640) µg L⁻¹ for adult tarek. Tarek exposed to fluvalinate and esfenvalerate showed toxic effects throughout the test, such as splashing, vigorous and then slower swimming, loss of balance, increased respiratory rate and contraction. Consequently, fluvalinate and esfenvalerate were found to be highly toxic to tarek and therefore the concentration of fluvalinate should not exceed 0.003 µg L⁻¹, and that of esfenvalerate should not exceed 0.005 µg L⁻¹ in freshwater environments where tarek lives.