Evaluation of growth performance, carcass yield, and proximate composition of fillets of male and female pirarucu (Arapaima gigas) during the fattening phase

The objective of this study was to evaluate the comparative growth performance, carcass yield, and the proximate composition of the muscle between male and female Arapaima gigas (pirarucu) during the fattening phase. Juvenile pirarucu (n = 114; 1126 ± 219 g; 55 ± 3 cm) were kept in 120 m2 brick tanks at a stocking density of 1.55 g m-2. Fish were raised under the same management conditions during 427 days and biometrics were performed monthly to evaluate the growth performance. Fish (n = 15 per collection day) were sampled at 91, 187, 273, 341 and 427 days to evaluate the carcass yield, proximate composition of the muscle and to determine its gender via histological analysis of the gonads. Data were analyzed using a multivariate statistical method. Growth performance, carcass yield and proximate composition of the muscle were similar between genders up to 427 days of rearing. The coefficients of variation in total weight and length that express the batch heterogeneity were higher for females throughout practically the whole experimental period. This was probably due to the dominance behavior between female fish, which also justifies why some females reached larger sizes at the end of the experiment. The yields for the fillet, abdominal muscle and loin were greater at 273 days compared to other sampling events, regardless of gender. Partial harvesting of pirarucu during the fattening phase can therefore be a management strategy for slaughtering fish with a higher meat yield. •The male and female pirarucu showed similar growth performance and carcass yield.•Female pirarucu showed greater size heterogeneity during the fattening phase.•Partial harvest during the fattening phase can be performed in Arapaima gigas.