Feeding rate for newly weaned tambaqui (Colossoma macropomum) juveniles in a recirculating aquaculture system

Determining the optimal feeding rate for fish is crucial to promote growth and feed efficiency, avoid wastage, and maintain water quality. Endogenous factors and the farming environment can influence the feeding rate. Therefore, the present study aimed to investigate the effects of five different feeding rates on water quality, growth performance and gene expression in newly weaned tambaqui (Colossoma macropomum) juveniles reared in a recirculating aquaculture system. Five feeding rates were tested in triplicate: 5 %, 10 %, 15 %, 20 %, and 25 % of biomass daily for 28 days. Dissolved oxygen levels were higher only in the fish tanks fed with 5 % of biomass. The greatest total length, length gain, length gain rate, weight, weight gain, weight gain rate, and specific growth rate were observed in tambaqui juveniles fed with 10 %, 15 %, 20 %, and 25 % of biomass, respectively. However, segmented regression analysis determined that the optimal theoretical total length and weight corresponded to feeding rates of 10.35 % and 11.87 % of biomass, respectively. Ghrelin and leptin were directly proportional to the increase in feeding rate, although there was no difference in the expression of myod and myog genes in tambaqui fed at different feeding rates. For optimal feed utilization and productivity, we conclude that feeding tambaqui juveniles at 11.87 % of biomass per day is most suitable for this species during the nursery phase in a recirculating aquaculture system.