Fish are widely recognized as bioindicators of aquatic pollution, reflecting the impact of pesticides on ecosystem integrity and human health due to their position in the food chain. Freshwater ecosystems, including lentic and lotic systems, sustain diverse fish populations whose survival is influenced by physicochemical parameters and environmental stressors. The mosquitofish (Gambusia affinis), owing to its wide distribution, adaptability, and high reproductive capacity, serves as an effective model organism in toxicological studies. In the present study, the LC50 value of the tested pesticide was determined to be 3 ppm, indicating moderate acute toxicity.

Biochemical analysis revealed a concentration- and time-dependent decline in protein content. After 24 hours of exposure, protein levels decreased remarkably from the control value (172 µg; OD 1.9) to 2.7 µg (OD 0.03) at 2.5 ppm. A further reduction was observed after 48 hours, with protein content reaching 1.8 µg (OD 0.02) at the same concentration. These findings suggest that the pesticide exerts significant toxic effects by disrupting protein metabolism, possibly through inhibition of synthesis or enhanced degradation, thereby indicating potential ecological risks in aquatic environments.