The Use of Hematological and Histopathological Biomarkers to Assess the Health of Aquatic Ecosystems in Koh Sichang, Thailand

Abstract Koh Sichang area in Thailand is a sink for a wide variety of contaminants such as heavily polluted water from industry and oil spills. This situation may affect the health status of fish living in the area, but such information remains scarce. In this study, we evaluated the health status of java rabbitfish Siganus javus, an important marine fish in Koh Sichang, using hematological and histopathological biomarkers. All fish samples were collected from the Koh Sichang area during December 2017 and January 2018. Although the salinity, pH, and dissolved oxygen levels at sampling points were all within the normal range, abnormal nuclei were observed in erythrocytes (up to ~6% of all erythrocytes) and in some leucocytes (neutrophil, lymphocyte and monocyte). Visceral organs (gill, kidney and liver) were apparently normal in terms of gross morphology, but a wide variety of the histopathological alterations were found at the microscopic level: epithelial hyperplasia and aneurysm in gills; blood congestion and melanomacrophage centers (MMCs) in the liver; renal degeneration, granuloma and MMCs together with unidentified parasites in kidney. Calculation of semi-quantitative parameters [histological alteration index (HAI) and the average value of alteration (AVA)] demonstrated the highest frequency of histopathological alterations in kidney, suggesting that kidney is a sensitive organ. Overall, our observations suggest that S. javus in Koh Sichang is under the pathological state and warrants conservation efforts. Keywords: Erythrocytes, Fish Health, Hematology, Histopathology, Kidney