Histopathology of Selected Economically Important Fish Species from the Escravos Estuary, Nigeria: A Baseline Study for Environmental Monitoring

Abstract

The estuarine environment is a major sink for potentially hazardous chemical pollutants emitted from industrial and domestic sources. Particularly, the Escravos estuary is vulnerable to crude oil spillage due to the numerous crude oil exploration and transportation activities. This could lead to the contamination of water and affect the health of aquatic organisms. In the present study, the histopathological structures of the liver and gills of three selected economically important fish species (Ethmalosa fimbriata, Pseudotolithus elongatus, and Caranx senegallus) from the Escravos estuary were studied. Fish samples were collected through fishers operating on the estuary using purse seine and gill nets. After the catch, the liver and gills were harvested, labeled, and prepared for photomicrography. Liver histopathology showed a diffused preponderance of macrovesicular steatosis, ballooning degeneration, and mononuclear inflammatory infiltrates in all target fish species. Whereas no observable lesion was observed in the gills of P. elongatus and C. senegallus, the gill histopathological evaluation of E. fimbriata indicated that the lamella appeared acellular with no evidence of epithelial cells. The observed discrepancy in alterations in the gills among the selected fish species could be attributed to the evolutionary history of fish species, age, and differences in species behavior, diet, or habitat preference. The study revealed that the liver was mostly affected. This is could be largely due to the recent government intervention in combating vandalism of crude oil facilities and oil theft which has played a crucial role in the significant improvement of water quality in the estuary.