How do temperatures affect the performance, muscular cellularity and physiological parameters of tambaqui (Colossoma macropomum) and hybrid tambatinga (C. macropomum x Piaractus brachypomus)?

Abstract This study evaluated the effects of different water temperatures on growth parameters, muscle cellularity and physiological responses of juveniles of tambaqui ( Colossoma macropomum ) and hybrid tambatinga (♀ C. macropomum × ♂ Piaractus brachypomus ) reared in a recirculating aquaculture system (RAS). A total of 224 juveniles (112 per fish group; initial weight of 1.31 ± 0.39 g) were distributed at 0.5 fish L⁻ 1 in 16 circular tanks (28 L each), in a completely randomized 2 × 2 factorial design with four replicates following treatment: CT 28 , HT 28 , CT 32 , and HT 32 , corresponding to the two fish group maintained at 28 °C or 32 °C for 30 days. Dissolved oxygen and water pH were lower at 32ºC ( P < 0.05). After 15 and 30 days, C. macropomum showed greater weight, weight gain, daily weight gain and biomass than the hybrid, regardless of temperature ( P < 0.05). Plasma protein showed an interaction effect, with higher values in tambatinga at both temperatures. In the comparison between fish groups, only HT 32 showed values higher than HT 28 (P < 0.05). Hemoglobin concentrations were higher for C. macropomum and 32ºC ( P < 0.05). Hepatosomatic and viscerosomatic indices were higher in C. macropomum at 28 °C (P < 0.05), while muscle cellularity varied between fish group and temperatures, with hybrid tambatinga presenting larger fiber diameters and 32 °C promoting hypertrophy (P < 0.05). Therefore, the temperature of 32 °C promoted short-term growth in RAS, particularly in juvenile C. macropomum , and induced genotype-specific physiological and muscular responses. However, considering the short duration of the study, further studies are needed to establish definitive recommendations.