Effects of feeding strategies on growth, biochemical parameters and waste excretion of juvenile arapaima (Arapaima gigas) raised in recirculating aquaculture systems (RAS).

Abstract An 8-week experiment (trial 1) was conducted to determine the optimal feeding frequency for juvenile Arapaima gigas. Seventy-two fish (500.0 ± 50.9 g, mean ± S.E) were randomly assigned to 12 tanks (500 l) in recirculating aquaculture systems (RAS). Four treatments with three replicates each were considered: T1) fish fed using self-feeders (free choice to eat); T2) fish fed by hand to apparent satiation twice daily (09:00 h, 17:00 h); T3) fish fed by hand to apparent satiation 3 times daily (09:00 h, 12:00 h, 17:00 h); T4) fish fed by hand at fixed rates (2% BW day-1) twice daily (9:00 and 17:00). After 60 days, growth parameters, biochemical indices in blood plasma and digestible enzyme activities were evaluated and water flow was closed to evaluate the effect of feeding strategies on total ammonia nitrogen (TAN) and phosphorous (P) accumulation. The results showed that growth parameters and body composition were not influenced by feeding strategies (p >.05). The biochemical analysis revealed no differences in glucose, cholesterol or aspartate aminotransferase (p >.05). However, alanine aminotransferase and alkaline phosphatase increased in the treatments with the lowest feeding frequency (twice daily – T2) p <.05. No differences in protease, amylase or lipase in intestine were found (p >.05). TAN excretion was lower in T1 (0.100 μg/ml) compared to T2 (p =.001). P excretion was low (0.470 g kg BW) in T1 fish compared to T2 (0.615, p =.011). In short, all the feeding strategies evaluated can be used without compromising arapaima growth. However, apparent satiety twice daily led to increased N and P excretion. Highlights • Arapaima can be fed efficiently with self-feeders, though there was no difference in growth parameters and body composition. • Alanine aminotransferase and alkaline phosphatase increased in fish fed under apparent satiation three times per day. • There were no significant differences in digestive enzymes in fish subjected to different feeding strategies. • Phosphorus and total nitrogen excretion was low in RAS system when fish was allowed to trigger the self-feeders. [ABSTRACT FROM AUTHOR]