Potential Influence of Shading in Freshwater Ponds on the Water Quality Parameters and the Hematological and Biochemical Profiles of Nile tilapia (Oreochromis niloticus Linnaeus, 1758)

Nile tilapia is a high-demand commodity in most developing countries including the Philippines, but its production is hampered by fluctuating water temperature (WT) and dissolved oxygen (DO) concentrations, which are mostly influenced by temperature warming. Net shading has been demonstrated to reduce pond temperature and increase the rate of spawning in cultured tilapia. The current study aimed to investigate the potential effects of shading on the water quality parameters, blood indices, and serum biochemical profiles of cultured Nile tilapia. Fish were collected from unshaded (control) and shaded (experimental) ponds in three breeding cycles. WT and DO concentrations were measured, while hematological and biochemical analyses were performed. The results showed that the average WT was considerably decreased in the shaded pond with no significant difference in the DO concentrations. Red blood cells, hemoglobin, and lymphocyte counts were significantly lower in fish raised in shaded ponds, although mean corpuscular volume and neutrophil counts were significantly higher. Likewise, Chole, TP, and Alb values were significantly affected by the interaction of cycle and shading setup. Cortisol, Glb, K+, Cl-, Mg2+, and TCa values showed significant differences and were only affected by the cycle. Similarly, AST and ALT values showed significant differences and were affected by both cycle and shading setup. Water quality parameters (WT and DO), hematological blood indices, and serum biochemical variables were correlated positively with each other. In brief, prior data imply that net shading can reduce WT in aquaculture ponds, reduce stress in Nile tilapia, and lessen the consequences of temperature warming on species production.