Effect of water velocity on intermediary metabolism of juvenile matrinxã fish (Brycon amazonicus)

Background: determination of water velocity for optimum fish growth is fundamental since its duration and intensity can interfere with the metabolic preference for some biochemical paths, resulting in the use of specific substrates for fish growth. Objective: the purpose of this study was to assess the metabolic adjustments of juvenile matrinxã (Brycon amazonicus) reared under various sustained swimming conditions (SS). Methods: fish were subjected to SS for 90 days at five swimming speeds: 0.0 (control), 1.0, 1.5, 2.0, and 2.5 Body Length per second (BL/s). At the end of the experimental period, fish were euthanized; samples of blood, liver, white-muscle, red-muscle and ventral muscle were collected and metabolite concentrations were evaluated. Results: fish reared between 1.0-1.5 BL/s increased the hepatosomatic index (HSI) while those swimming at velocities higher than 1.5 BL/s showed diminished HSI and visceral fat. Fish under moderate swimming utilized visceral fat to supply energy for red muscle contractions while white muscle of fish swimming at higher speeds used carbon backbones from amino acids plus visceral fat. Conclusion: sustained swimming between 1.0-1.5 BL/s enhanced the intermediary metabolism of B. amazonicus, improving fish performance. Future studies linking macronutrient dietary levels and SS should allow adjusting rearing conditions under SS to optimize growth versus metabolic performance.