Blood chemistry profile of Surubim hybrid fish (Pseudoplatystoma reticulatum X P. corruscans) raised in different stocking densities

Massive production, such as fish growing in water recirculation system, imposes challenges to animals capable of altering their homeostatic balance, and is able to affect their physiological performance. Therefore, the levels of ions and serum enzymes can be used as indicators of fish health. This study aimed to analyze the blood biochemistry profile of hybrid surubim (P. reticulatum X P. corruscans) submitted to different stocking densities in water recirculation system, in two distinct stages of production, from 150 to 400 g (first trial), and 400 to 1000 g (second trial). In the first trial, the five stocking rates were: 27.5, 47.5, 67.5, 87.5 and 107.5 fish/m³ of water. To obtain these densities, it was used 11, 19, 27, 35 and 43 fish per tank, respectively. In the second trial, five stocking rates were: 10, 20, 30, 40 and 50 fish/m³ of water. To obtain these densities we used 4, 8, 12, 16 and 20 fish per tank, respectively. The concentrations of glucose, cholesterol, triglycerides, urea, creatinine, alkaline phosphatase (ALP), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), calcium, phosphorus, potassium and magnesium were obtained. Only urea concentrations in first trial and ALP and AST concentrations in second trial were influenced by stocking density, presenting a significant difference between groups. Thus, in both trials the hybrid fish studied maintained homeostasis when reared in different stocking densities