WATER QUALITY‐TILAPIA AUREA INTERACTIONS IN PONDS RECEIVING SWINE AND POULTRY WASTES

Juvenile Tilapia aurea were reared from June through early October, 1976 in ponds at densities of approximately 6,000/ha with the following treatments: 1) control, 2) 210 laying hens/ha, 3) 222 hogs/ha, 4) 74 hogs/ha, and 5) 25 hogs/ha. Poultry or swine were maintained over the ponds in suspended cages and slotted floor pens, respectively, to allow waste products and spilled feed to fall directly into the water. Rapid growth of T. aurea occurred throughout most of the experiment in the ponds receiving chicken waste and the two lowest levels of hog waste. Poorest fish growth was obtained in the pond receiving the highest level of hog waste, with the non-fed control fish demonstrating slightly better growth than those in the 222 hogs/ha pond. A complete fish kill occurred in the pond receiving the intermediate level of hog waste near the termination of the experiment. It is hypothesized that a combination of deteriorating water quality and the complete coverage of the pond surface by duckweed contributed to the mortality. Dissolved oxygen (DO) levels were satisfactory in the control ponds and the pond receiving poultry waste, and were generally acceptable in the 25 hogs/ha pond. Morning DO levels (between 0800 and 1030) of less than 2.0 mg/l were common in the other two ponds receiving hog waste. Ammonia levels (as NH3 nitrogen) were generally low except in ponds receiving the waste from 222 and 74 hogs/ha. Values in the 222 hogs/ha pond reached in excess of 50 mg/1 and contributed to the high level of mortality which occurred in that pond during the experiment. T. aurea reared on poultry and swine wastes can be used directly for human consumption or they can be fed back to the livestock as a feed supplement. In addition, the use of ponds to collect terrestrial animal waste eliminates many of the odor and fly problems associated with animal feeding operations.