STABLE ISOTOPE ANALYSIS IN AMAZON RIVER PRAWN AND TAMBAQUI FARMED IN DIFFERENT CULTURE SYSTEMS
Stable isotops composition is an important tool for trophic web studies. This frame may be very useful in aquaculture to define the main food items of a species inside ponds. Amazon River prawn, Macrobrachium amazonicum and the fish tambaqui, Colossoma macropomum are important species for Brazilian Aquaculture. Both inhabit Amazonia rivers and have similar environmental requirements. Thus, the culture of both species in integrated multi-trophic aquaculture system is possible and may be more efficient and sustainable than the monoculture.
The aim of this research was to analyse the 13C e 15N isotops composition in the muscles of the Amazon River prawn and tambaqui farmed in different culture systems. An experiment was performed following a completely randomized design, with three treatments and four replicates each. The treatments were: T1_freshwater prawn monoculture, T2_polyculture of freshwater prawn and free tambaqui, T3_polyculture freshwater prawn with fish in cage, during five months. The water variables were measured daily and food provided consisted of specific feed for fish (Fri-Ribe 32% CP) and marine shrimp (Guabi Potimar, 38% CP) in monoculture systems. For polyculture systems, only the fish received the inert diet.
Samples of prawn and fish muscles were collected at the end of the experiment. After, these samples were submitted to stable isotopes analysis of 13C e 15N by Isotope ratio mass spectrometry (IRMS) coupled to the elemental analyzer. The results were presented (‰) according to the international standard Pee Dee Belemnite - PDB and the atmospheric nitrogen - N2 for carbon and nitrogen.
There were significant differences among the culture systems for prawn (p < 0.05), but not for tambaqui (Table 1). These results may be related to the difference in food eat by animals. In prawn monoculture commercial feed was suplyed, whereas in polyculture prawns ate wastes of diet supplied to tambaquis and fish feaces. On the other hand tambaqui eat the same commercial diet in all systems.