Polyculture of freshwater prawn (Macrobrachium rosenbergii) and red seaweed (Gracilaria tenuistipitata) following biofloc technology with partially reduced feed rations

Abstract

Study on the polyculture of freshwater prawn (Macrobarchium rosenbergii) with red seaweed (Gracilaria tenuistipitata) following biofloc technology was randomly arranged with five different feeding rations for 75 days. The control group (monoculture) was fed a commercial feed at 100% feed ration (8% of biomass per day). The four other groups were co-cultured with red seaweed (1.5 kg/m3 ) and received commercial feed at 100%, 80%, 60%, and 40% feeding ration of the control. Prawns (initial weight of 0.48 g) were reared at a density of 200 ind/m3 in the 150-L tank at a salinity of 5 ppt. Molasses was used as a carbon source to maintain a C:N ratio of 17.5:1. Results showed that the concentrations of TAN and NO2 - in the coculture tanks were much lower than in the monoculture. The growth rate and production of prawns in the 60% feeding ration treatment were comparable to those in the control group (p>0.05). However, prawn performances were reduced at 40% feeding rates and were significantly inferior to the control group (p<0.05). The feed conversion ratio (FCR) was lower at lower feeding rates. These results indicated that the polyculture of prawn-Gracilaria supplied at 60% feed ration, which could reduce FCR by 57.71%, still obtained normal growth as well as maintained better water quality.