Principle of Aquaculture (1+1)

Methods

The following methodology for a 0.4 ha pond exemplifies the technology.
1. Prepare the pond using the urea-bleaching powder method or by draining-drying in June.
2. Stock the pond with 2 000 (5- 8 g) fingerlings of six Asiatic carps: catla, 20; rohu, 25; mrigal, 20; silver carp, 20; grass carp, 5; and common carp, 10.
3. Fertilize the pond daily with 30 litres of biogas slurry. The slurry is rich in nitrogen and phosphorus, and is free from toxic gases which are produced when cow dung decomposes in ponds.The slurry is not applied on a cloudy day or when the fish come to the surface to gulp air.
4. Surface feeders will have reached about 1 kg individual body weight in 6 months. All marketable fish are then harvested every 2 months and replenished with an equal number of fingerlings. A total of 2 000 kg of fish is obtained using biogas slurry as against 800 kg if raw cow dung is used.