Histopathological Effects of Aquafarming on the Liver and Testes of Nile Tilapia (Oreochromis niloticus L.) from Taal Lake, Philippines

Abstract

Background: The intensive fish cage farming in Taal Lake ecosystem has generated socioeconomic benefits for the community. However, accompanying these gains is the continuous deterioration of the aquatic system and consequent decline in the quality of fish health. The present study attempted to investigate the impact of aquafarming on the general health, as well as on liver and testes histology of Oreochromis niloticus L. in Taal Lake.

Methodology: Water and sediment samples from the three sites of varying degrees of aquaculture were obtained for physicochemical analysis. Ten male adult tilapia samples were also obtained and subjected to gross examination, which included the computation of the necropsy-based fish health assessment index (NFHAI), condition factor (CF), hepato-somatic index (HSI), and gonado-somatic index (GSI). Qualitative and semi-quantitative histological analysis based on the level of histological alterations in the liver and testes were also done.

Results and Conclusion: CF, GSI, and HSI values showed that tilapias from the aquaculture sites (Banyaga and Balakilong) experienced organ degeneration. Semi-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 melanomacrophage 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. Histopathological observations were attributed to high levels of ammonia and copper detected in the lake.