Acute Toxicity and Behavioural Responses of Amur Common Carp (Cyprinus carpio haematopterus) Exposed to Carbofuran Pesticide

Abstract

Carbofuran is a highly toxic carbamate pesticide widely used in agriculture and frequently detected in aquatic environments, where it poses risks to non-target aquatic organisms. This study determined the acute toxicity and behavioural responses of Amur common carp (Cyprinus carpio haematopterus) fingerlings exposed to different concentrations of carbofuran under laboratory conditions. A 96-h acute toxicity bioassay was conducted using carbofuran concentrations of 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 and 1.7 mg/L, together with a control. Mortality and behavioural responses were recorded at 24, 48, 72 and 96 h, and the median lethal concentration (96-h LC₅₀) was estimated using probit analysis. The 96-h LC₅₀ value of carbofuran for C. carpio haematopterus was estimated as 1.33 mg/L, indicating high acute toxicity under the experimental conditions. Exposed fish displayed concentration- and time-dependent behavioural alterations, including hyperactivity, erratic swimming, increased opercular ventilation, frequent surfacing, lethargy, excessive mucus secretion, fin clamping, reduced responsiveness to external stimuli and respiratory distress. In contrast, control fish maintained normal swimming activity, feeding behaviour and responsiveness throughout the experimental period. The physicochemical characteristics of the test water remained relatively stable, although dissolved oxygen declined during the later exposure intervals. The observed behavioural abnormalities and mortality suggest that carbofuran can disrupt normal physiological and neurobehavioural functions, probably through acetylcholinesterase inhibition. These findings indicate that behavioural responses may serve as sensitive indicators of pesticide-induced stress and highlight the ecological risk of carbofuran contamination to freshwater fish populations and aquatic ecosystems.