Using stable isotopes (C and N) to determine plankton contribution in tambaqui juvenile growth in earthen ponds

Tambaqui production is commonly performed in fertilized ponds, considering that this species feeds from zooplankton throughout its life. This study evaluated plankton’s participation in the production of tambaqui juveniles in ponds using different stocking densities. A total of 72,000 fish (1.9 ± 0.01 cm and 0.4 ± 0.1 g) were stocked in 12 ponds (600 m 2 ), in the densities of 5, 10, or 15 fish.m −2 , with four replicates in a completely randomized design. Fish were fed twice a day to the point of satiety, with a commercial diet containing 36% of crude protein for 56 days. Zootechnical performance parameters were evaluated, and limnological variables were monitored. With the aid of stable isotopes, both the diet and plankton participation were assessed in the produced biomass of fish. Turbidity and Secchi were the only limnological variables that varied due to stocking density, while final biomass and final average density were the only zootechnical indexes that presented differences. Plankton contributed to the formation of muscles throughout the production period, with an average participation of 22.75 ± 12.82%.