Effects of water management practices on discharge of nutrients and organic matter from channel catfish ( Ictalurus punctatus) ponds

Abstract

A water quality data set generated by sampling commercial ponds for 2 years was used in a hydrological model of pond overflow volume to describe the effects of water management practices on discharge of nutrients and organic matter from channel catfish Ictalurus punctatus ponds in northwest Mississippi, USA. Average concentrations of total nitrogen, total phosphorus, chemical oxygen demand, and biochemical oxygen demand in pond waters were highest in the summer but waste discharge was strongly influenced by pond overflow volume, and the model indicated that greatest quantities of nutrients and organic matter were discharged in the winter when pond overflow volume was greatest. The model also showed that managing pond water levels to maintain a minimum 7.5-cm water storage potential reduced average discharge of nitrogen, phosphorus, and organic matter in pond overflow by about 70% compared with ponds not managed to maintain storage potential. The model further showed that harvesting fish without draining ponds between fish crops could reduce average annual nutrient and organic matter discharge by over 60% relative to annually drained ponds. Maintaining water storage potential and not draining ponds between fish crops therefore appear to be simple and effective methods of reducing waste discharge from aquaculture ponds and have the added benefit of substantially reducing the need for pumped water to maintain pond water levels.