Histopathology of Liver and Kidney of the River Catfish (Mystus nemurus) as a Bioindicator of Satui River Water Quality, South Kalimantan, Indonesia

Due to their ability to accumulate pollutants, fish are commonly used as bioindicators in river ecosystems. Their direct contact with dissolved substances has given the chance for the livers and kidneys of fish to be affected by chemical changes in aquatic environments. Thus, concerns have emerged regarding the potential degradation of water quality in the Satui River due to human activities, where Mystus nemurus is commonly found. In response, this study aimed to evaluate the histopathological alterations in the liver and kidney of the river catfish, as well as assessing the water quality of the Satui River. Histopathological lesions are detected through paraffin-based microtechniques. While pollution Index methodology is employed to evaluate river water quality according to the Water Quality Standards as specified in Government Regulation No. 22 of 2021 of the Republic of Indonesia. The present study utilized a scoring-based qualitative descriptive histopathological analysis to investigate the histological characteristics of the liver and kidneys. The Satui River's water quality was classified as "lightly polluted" based on the average pollution index values of 1.11 and 2.31 for the first and second samplings, respectively. Fat degeneration, congestion and necrosis were monitored as the characteristic features of liver histopathological damage in river catfish. Simultaneously, the histopathological analysis discloses the existence of melanomacrophage center (MMC), congestion and glomerular swelling as observable manifestations of kidney damage. Based on the obtained scoring results, a score of 1 was recorded, which indicates the occurrence of relatively minor damage, encompassing a range of 25-50%. Between stations 1 & 2, no significant difference (P> 0.05) was observed in the histological damage for the liver and kidneys of river catfish. To conclude, the utilization of histopathological assessment for river catfish offers significant benefits since it allows accurate evaluation of the health of both fish and water at any given time.