International Journal of Agriculture and Sustainable Development July 2025|Vol 07 | Issue 03 Page |301 Estimation of Lethal Concentrations of Chlorpyrifos and Its Effect on Behavioral and Hematological Parameters in Exposed Cyprinus Carpio Omar Zahid 1 , Rooh Ullah 1 , Ikram Ilahi 2 , Syed Ihteshamullah *1,3 , Muhammad Yousaf 1 , Akhtar Rasool 1,4 and Naseer Ullah *1 1 Centre for Animal Sciences and Fisheries, University of Swat, Pakistan 2 Department of Zoology, University of Malakand, Pakistan 3 Department of Zoology, Hazara University, Mansehra, Pakistan 4 Center for Biotechnology and Microbiology, University of Swat, Pakistan * Correspondence: *naseer@uswat.edu.pk (NU); *syedihtesham15@gmail.com (SI) Citation| Zahid. O, Ullah. R, Ilahi. I, Ihteshamullah. S. I., Yousaf. M, Rasool. A., Ullah. N, “Estimation of Lethal Concentrations of Chlorpyrifos and Its Effect on Behavioral and Hematological Parameters in Exposed Cyprinus Carpio”, IJASD, Vol. 07 Issue. 3 pp 301-309, June 2025 Received| June 19, 2025 Revised| July 02, 2025 Accepted| July 04, 2025 Published| July 06, 2025. esticides are harmful to humans, birds, fish, and other organisms. Chlorpyrifos is an insecticide (organophosphate) used universally in farming and home settings around the world to control pests. Assessing damage caused by pesticides is very crucial to find out their harmful effects on non-targeted fauna. The current research was designed to identify the toxicity and harmful impact of Chlorpyrifos on the mortality, behaviour, and haematology of Cyprinus carpio. The lethal concentrations were observed for 24, 48, 72, and 96 hrs. The behavioral and hematological alterations were also observed in the groups exposed to Chlorpyrifos. The LC0 was determined as 0.08, 0.10, 0.15, and 0.19 mg/L for 24, 48, 72, and 96 hrs. The LC50 was found to be 0.160, 0.18, 0.21, and 0.48 mg/L for 24, 48, 72, and 96 hrs, while the LC100 values were found to be 0.32, 0.64, 0.96, and 1.28 mg/L for 24, 48, 72, and 96 hrs. Changes in behaviour, such as loss of body balance, irregular swimming, etc, have been observed. A significant change in haematological parameters has been determined in experimental groups as compared to the control (p < 0.05). It has been concluded that chlorpyrifos has a lethal effect on Cyprinus carpio. Keywords: Chlorpyrifos; Cyprinus Carpio; Lethal Concentration; Pesticide; Swat and Toxicity. Introduction: Pesticides like Chlorpyrifos (CPF) and Cypermethrin (CYP) are extensively used in Pakistan for the large-scale control of pests and insects in crops, vegetables, and fruits [1]. However, these pesticides belong to a class of environmental toxins known to cause significant harm to non-target organisms. Numerous studies have reported both acute and chronic toxic effects of these chemicals on aquatic life, particularly fish, with residues commonly detected in various fish tissues [2]. Fish may exhibit modifications in various haematological parameters when exposed to different chemical substances, which are commonly used to assess fish health. Haematology has long been used to detect physiopathological changes in response to a diversity of stressors. Consequently, the most frequent way to find out the sublethal impacts of contaminants is to use haematological tests [3]. Chlorpyrifos (CPF) is a broad-spectrum organophosphate insecticide extensively used in agricultural and domestic applications worldwide [4]. It is the second most widely used organophosphate (OP) [5]. Organophosphates (OPs) have gotten a lot of attention in Pakistan P