Pen culture of Macrobrachium amazonicum: use of artificial diet and impact on benthic community

The pressure on the benthic macroinvertebrate community and the use of artificial diets were evaluated during the pen rearing of Macrobrachium amazonicum. The study followed a completely randomized design with three treatments and three repetitions: treatment no prawns, no feed (noPnoF); treatment prawns, no feed (PnoF); and treatment prawns, feed (PF). Six pens were stocked with 10 prawns m^?2 with average initial weight of 0.63 ± 0.05 g and average length of 4.28 ± 0.14 cm; the other three pens were not stocked with prawns. Every 10 days, prawn biometry was carried out and samples were collected from the water and the sediment in each pen. The results showed that the limnological variables remained adequate for the species' biology. The zootechnical indices did not differ significantly (P > 0.05) in weight, total length and survival, with values of 4.43 ± 0.93 g, 8:03 ± 0:43 cm, and 80 ± 9.6%, respectively, for the treatment PnoF, and 4.83 ± 1.03 g, 8.42 ± 0.51 cm and 73 ± 3.5% for treatment PF. The macroinvertebrate analyses showed a significant difference (P < 0.05) for the total abundance of Oligochaeta among the days of collection and for Polymitarcyidae among the treatments. It is therefore concluded that the presence of prawns affects the abundance in the benthic community and that the zootechnical performance of M. amazonicum in this experimental condition is not influenced by supplied artificial feed.