How To Calculate Fish Pond Carrying Capacity Using Stocking Density

Each pond has a carrying capacity or production capacity based on species of fish, water quality, temperature and quality of fish feeds. All agricultural activities have such a carrying capacity. A maize farmer would space planting his seeds at certain distances apart to allow for maximum production; too many seeds planted too close together would produce a small crop. The same is true for fish. Under the best of conditions in static earthen ponds in Nigeria, catfish productions of 10-12 tons per hectare have been achieved although some farmers claim productions up to 50 tons per hectare. This is possible as Asian catfish farmers achieve productions up to 200 MT/ha/ year. For yields of 50 MT, it is necessary to stock ponds with catfish at a density of 6 fish/m2. This would assume a mortality of up to 20% and harvested fish averaging about 1 kg each in weight. Still many ponds are routinely stocked at 5-10 fish/m2. During rearing of juveniles, densities may be 50 fish/m2 or even more as their density would be reduced upon stocking in production ponds. Many fish farmers rearing fish in concrete block tanks stock fish for grow out at 15 to 30 catfish/m2 and achieve total productions of 750 kg in six months from 3 tanks of about 50m2 total surface area. This extrapolates to a production of 300 MT/ha/year, but this is by using the tanks in a partial flow through system to remove wastes and foul water with regular flushing of water. The less hardy tilapias cannot be stocked at such densities as Clarias as their tolerance for limiting conditions of low oxygen and accumulation of waste are very limited in comparison with catfish.