Freshwater aquaculture (2+1)

Unit 3 - Nursery, Rearing and grow-out ponds

3.3.2. Supplementary feeding
When fish are stocked at high stocking densities, the natural food produced through fertilization and manuring may not be sufficient to sustain high growth in shorter period of time. Hence, the stock has to be fed with supplementary feeds. Commonly, supplementary feeds such as mixture of rice bran or wheat brawn mixed with oil cakes such as groundnut cake or mustard cake or cotton seed cake and other cakes are used in a ratio of 1:1. In order to improve the quality of feed to get better growth and production, extra ingredients such as fish meal, soya flour, vitamin and mineral mixtures could be added to the feeds. The feed mixture is generally mixed with appropriate quantity of water and made in dough which is then shaped into a form of ball or cake is either broadcast into the ponds or kept in feeding trays at several places in the pond.

Feeding rates vary according to the size of the fish. Spawn are fed at a rate of 8-10% of the biomass, while fry when stocked in rearing ponds up to fingerlings stage are generally fed @ 6-8% of the standing crop. In grow-out ponds the fish are fed initially at a rate of 5% which is gradually decreased to 2-3% biomass till harvest. Periodic sampling of the stock is necessary to estimate the biomass and adjust feeding rates.