Histopathological Alterations in Clarias gariepinus from Biu Dam, Borno State, Nigeria as Indicators of Aquatic Pollution

Abstract

This study assessed heavy metal concentrations and associated histopathological alterations in Clarias gariepinus (African catfish) from Biu Dam, Borno State, Nigeria. Water and fish tissue samples were collected monthly from three sites (Main Dam Area, Dam Slope Area, and Gwalam Area) over six months (March–August 2024). Heavy metal concentrations (Arsenic, Cadmium, Chromium, Copper, Lead) in water and fish tissues (gill, liver, kidney, heart) were determined using Atomic Absorption Spectrophotometry, while histopathological examination was conducted using standard light microscopy with Haematoxylin and Eosin staining. Results revealed alarmingly high metal concentrations in water, with Arsenic (0.31±0.02 mg/L) and Lead (0.13±0.02 mg/L) exceeding WHO/FAO permissible limits by 31-fold and 130-fold, respectively. Correspondingly, catfish tissues showed significant bioaccumulation, with the liver accumulating the highest Arsenic concentration (0.045±0.005 mg/kg) and the heart showing elevated Cadmium (0.038±0.005 mg/kg) and Lead (0.028±0.004 mg/kg). Histopathological examination revealed severe tissue alterations, including gill filament necrosis, extensive hepatocyte necrosis with vascular congestion, renal tubular necrosis, and cardiac inflammation. Seasonal analysis showed significantly higher Arsenic (p=0.024) during the wet season and higher Copper (p=0.014) during dry season. The study concludes that C. gariepinus from Biu Dam is exposed to hazardous levels of heavy metals, resulting in severe histopathological damage across vital organs, posing significant ecological and public health risks to dependent communities.