BIOENERGETICS-BASED MODEL TO DETERMINE GROWTH, FEED REQUIREMENT AND WASTE OUTPUT OF GIBEL CARP (CARASSIUS AURATUS GIBELIO)

Fish growth model, feed requirement model and pollution output prediction model play a vital role in the management of fish culture operations. This study collected numerous literature data about the growth of gibel carp (weight 0.25—550 g) to calculate the growth rate using SGR, DGC, TGC and ADG growth models. The least squares method was used to optimize the growth coefficient within each growth stanza and to choose the best growth model. The TGC model showed that gibel carp has 3 growth stanzas in its life cycle: from first-feeding (0.25 g) to 13.1 g (Stanza 1); from 13.1 to 172.8 g (Stanza 2); and >172.8 g (Stanza 3). Results indicated that the modified TGC model produced a better fit of the growth trajectory of gibel carp than other models (SGR, DGC, ADG) in practical aquaculture operations. Feed requirement of fish in different growth stages was determined by digestible energy requirement (DEreq) based on the summation of expected energy gain, basal metabolism, heat increment of feeding, and urinary and branchial excretion. It was estimated that the requirement of digestible energy was about 1.94×10⁷ kJ, for gibel carp with a weight of 0.25—506 g. A nutrient mass balance method was used to estimate waste output when gibel carp at different growth stages were fed with 43%, 37%, 31% crude protein, respectively. Similarities in live body weight, weight gain and FCR between the observed values and predicted values revealed that the proposed model produced highly reliable estimates of growth performance, feed requirement and waste output for gibel carp farmed.