Biomarker Evaluation in Nile Tilapia (Oreochromis niloticus) to Assess the Health Status of Aquaculture Areas in the Seven Lakes of San Pablo

The seven lakes of San Pablo have been subjected to different degrees of stresses brought about by intensive aquaculture, sewage discharges, and other anthropogenic disturbances, which could have serious implications on the health of these ecosystems. This study was conducted to assess the health condition of cage aquaculture areas in the lakes using biomarkers in the adult Nile tilapia (Oreochromis niloticus). A total of 84 cultured fish samples consisting of 12 individuals per lake were examined to determine the condition factor (K-factor); hepatosomatic index (HSI); splenosomatic index (SSI); and histopathological features of the liver, spleen, and gills. The measured values for K-factor are suggestive of isometric growth and good health condition; however, fish from Sampaloc Lake had relatively lower values in comparison to the other groups. Although all liver samples had normal microstructure, the HSI of fish in Sampaloc and Palakpakin Lakes was significantly reduced than those obtained in fish from Lakes Bunot, Calibato, and Yambo. All spleen samples showed melanomacrophage centers (MMCs), with fish in Calibato Lake having higher SSI compared to the others. The majority of the gill samples showed minimal to mild clubbing of secondary lamellae, thrombosis, and aneurysm. Based on the endpoints considered in this study, Yambo Lake had the most optimal condition for fish culture. Lakes Sampaloc, Palakpakin, and Mohicap – on the other hand – had the lowest environmental status.