DOI: https://doi.org/10.36347/sajb.2026.v14i03.004

Pages: 218-232

Labeo rohita is a member of the Cypriniformes and Cyprinidae families. It is also referred to as rui, rohu, and rohit. Thirty Labeo rohita fish, measuring twenty to twenty-five grams, were acquired for the current study from a fish seed farm in Head Balloki, Punjab, Pakistan. After applying the experiment samples were sent to laborteries for hematological and histopathological examination. The toxicological consequences of nickel chloride on the freshwater fish species Labeo rohita (Rohu) are examined in this study. The mean corpuscular hemoglobin (MCH) in the low and high-dose groups increased from 21.0 fL in the control group to 38.8 fL and 47.0 fL, respectively, according to hematological analysis. Additionally, there was variation in hemoglobin levels, which went from 8.06 g/dL in the control group to 6.3 g/dL in the low-dose group and then up to 8.5 g/dL in the high-dose group. White blood cell (WBC) counts showed a significant decline; the control group recorded 36.33 ×10³/µL, whereas the low and high-dose groups recorded 30.33 ×10³/µL and 25.66 ×10³/µL, respectively. In contrast, the numbers of red blood cells (RBCs) rose in all experimental groups; in the low and high-dose groups, they were 1.66 ×10⁶/µL and 1.3 ×10⁶/µL, respectively, compared to 1.14 ×10⁶/µL in the control group. These results imply that Labeo rohita is exposed to nickel chloride, which causes notable physiological and cellular changes that may jeopardize the species' survival in contaminated aquatic settings. The study concentrated on hematological parameters and histological alterations in the gills after exposure to different nickel chloride concentrations. Significant gill injury was found, as evidenced by secondary lamellae shortening, hypertrophy, filament structure fusion, and gill epithelial hyperplasia. The findings emphasize how crucial it is to monitor and manage nickel pollution in aquatic environments to safeguard aquatic species that are essential to the survival and biodiversi