Histopathological effects of aquafarming on the liver and testes of Nile tilapia (Oreochromis niloticus L.) from Taal Lake (Philippines)

Abstract

The present study investigated the impact of aquafarming on the liver and testes histology of Oreochromis niloticus L. in Taal Lake by comparing samples from three sites with varying degrees of aquaculture. Water and sediment samples were obtained for analysis from Gonzales, the reference site, and Banyaga and Balakilong, the aquaculture sites. Ten male adult Tilapia samples were obtained from each site and were subjected to gross examination through the computation of the Necropsy-based Fish Health Assessment Index (NFHAI). The length of the fish, as well as the weight of the fish, the liver and the testes were measured and used for the calculation of the Condition Factor (CF), Hepatosomatic Index (HSI), and the Gonadosomatic Index (GSI). Liver and testes samples were subjected to qualitative and quantitative histological analysis. Liver samples were also checked for glycogen content through Periodic Acid Schiff staining. Tilapia from Banyaga gave the highest CF values, indicative of overnutrition. GSI and HSI values showed that tilapia from the aquaculture sites experience organ degeneration. Quantitative histological analysis and NFHAI showed a direct relationship between frequency of macroscopic and microscopic lesions and the intensity of aquaculture. Necrosis and hemorrhage were observed in both organs. Nuclear alterations, increase in melano-macrophage centers, fatty degeneration, and decrease in glycogen reserves were uniquely seen in the liver, while disorganization of lobules, lifting of the basement membrane, and intersex were seen in the testes. Observed external changes were attributed to congestion. On the other hand, histological differences were attributed to high levels of ammonia and copper observed in the lake. Clearly, aquaculture has an effect on the overall health of the Nile tilapia in Taal Lake.