MODELING JUVENILE TAMBAQUI Colossoma macropomum GROWTH IN AQUAPONICS SYSTEMS UNDER DIFFERENT STOCKING AND FEEDING RATES

In 2018 Brazilian native fish culture accounted for 38% of the national aquaculture production being the Amazonian fish tambaqui the most produced species. Since aquaponics is a globally growing aquaculture technology, studies that evaluate the performance of tambaqui in aquaponics systems are needed. Growth models are an option to formally describe fish growth and consequently culture performance all along the culture period. These models serve also as a tool to make managerial decisions. A 34-day trial culture of tambaqui and lettuce in permanently coupled aquaponic systems was carried out during the summer in Brazil. The research facility comprises 16 experimental aquaponic units, each one containing one fish tank (0.38m-3), 3 plant beds (0.42 m2 of surface and volume of 60 L each), and filtering systems.  Four fish stocking rates (50, 100, 150 and 200 fish m-3) were combined with four feeding rates. The base feeding rate (E) was adapted from the recommended by the Brazilian Agriculture Research Corporation (EMBRAPA) and a value of 1.5% was added (E+1.5%) or the values of 1.5 or 3% were subtracted (E-1.5%, E-3% respectively) to stablish the other feed rates, totaling sixteen combinations. Fish with initial average weight of 16.88 g were introduced in the systems according to the corresponding stocking rate and at least 10% of the fish of each system were weighted weekly to adjust the feeding rates. With the weight (g) data, and after outlier elimination, the Von Bertalanffy, Champan-Richards, Gompertz, monomolecular and logistic growth models were tested. The model that best adjusted to tambaqui growth in the aquaponics systems cultured with lettuce was the logistic one, , were W is the weight in the respective culture day (t), and ,, the growth model parameters (Table 2).  The models were validated through the Theil index which was minor than 0.2 in each case.

These growth models may be used to compare the tambaqui performance in aquaponics in other seasons or with other production technologies. Likewise, it may be useful as input for analysis of stocking and feeding rate optimization, bioeconomic analysis or system modelling.

Financial support: FAPESP (2018/23658-5, 2018/23605-9, 2017/50431-9), CNPq (311108/2017-2).