An energy budget and efficiency of sewage-fed fish ponds

An energy computation of a serially-connected, sewage-fed fish pond system was made. The annual solar radiation was 4456•2 MJ/m2. The synthetic efficiency of solar radiation to different fish ponds varied from 0•46 to 1•24%. The total energy input and phytoplankton production in ponds ranged from 11328 to 29082•2 MJ/y and 8•89 to 23•60 kg/m2/y, respectively. The gross conversion efficiencies of total, photosynthetic, biological and biological-industrial energy varied from 0•58 to 3•3%, 1•5 to 6%, 0•95 to 11•1% and 0•92 to 10%, respectively, in different fish ponds. The gross energy consumption for the production of fish varied from 116•9 to 732•5, 68•9 to 275•8, 34•9 to 443•7 and 38•9 to 456•8 MJ/kg fish for total, solar, biological and biological-industrial energy, respectively, in different ponds. The selection of fish species and maintenance of optimum physico-chemical and biological parameters are suggested to improve the energy transformation in sewage-fed fish ponds.