Research verification of four commercial scale split-pond designs

Abstract

Split ponds are earthen ponds divided into two sections: a small fish-confinement basin and a larger water-treatment basin. Water is circulated between the two basins using a high-volume pump. Although split ponds have proven their potential to increase the productivity of earthen catfish ponds, various pumping systems have been used in commercial settings. Choice of the best pumping system requires systematic verification of production and economic performance at commercial scale. In this study, we evaluated four commercial-scale design variants of split-pond systems. These four designs were primarily differentiated by the mechanism of water circulation between the fish-confinement and the waste-treatment sections. The water-moving devices include the slow-rotating paddlewheel, modified-paddlewheel aerator, screw pump, and axial-flow pump. This study investigated the production, economic, and investment feasibility of these four split-pond designs under controlled conditions over multiple years. An economic engineering approach using standard enterprise budget analysis was used to develop estimates of annual costs and returns for producing foodsize hybrid catfish from four split-pond systems. The additional investment capital required for converting a traditional open pond to any of the four split-pond designs ranged from $54,400 to $71,150 per 4-ha pond. The cost of production of the four split-pond designs ranged from $2.02/kg to $2.37/kg and was less than the 3-year average fish price. Higher breakeven yields are required to cover total costs, indicating increased financial risk associated with these intensive-production systems. Net present value (NPV) was highest for the modified-paddlewheel aerator design ($223,893/4-ha pond) and lowest for the screw-pump design ($74,621/4-ha pond). Similarly, the modified-paddlewheel aerator design had the highest modified internal rate of return (31%) while the screw-pump design had the lowest returns (27%). The economic and investment feasibilities of the four split-pond designs were sensitive to the prices of fish and feed. All four designs were economically feasible under current economic conditions with the modified-paddlewheel design showing greater economic potential for adoption.