Freshwater aquaculture

Unit 3 - Nursery, Rearing and grow-out ponds

3.3.1. Stocking

Nursery, rearing and stocking ponds are stocked with spawn, fry and fingerlings respectively. They need to be acclimatized in ponds before stocking to prevent abrupt changes in water quality which will stress them resulting in poorer survival.
 
Generally mono-culture is followed in nursery and rearing ponds, while poly-culture of carps in followed in grow-out ponds. When rearing space is limited polyculture is also followed in the rearing ponds.
Grow-out culture of carnivores is done under monoculture.
 
The stocking densities followed vary according to the level of management that can be under taken. For example when carp spawn are stocked in earthen nursery ponds, a stocking density of 300 to 500 numbers per m2 of pond area, while, stocking densities of 1000 t0 2000 numbers per m2 followed when they are stocked in cement tanks where, higher level of management is followed.
 
Rearing ponds are stocked with carp fry @ 20 to 30 numbers per square meter in rearing ponds while carp grow out ponds are stocked @ 5000-1000 numbers per hectare when polyculture is followed.
 
Stocking has to be done in cool hours, early morning is better, but they can be stocked in evenings or nights. One disadvantage of stocking early in the morning in fertilized ponds is that if plankton bloom is heavy, dissolved oxygen could be less in the early morning. The disadvantage if stocking in the evenings is that the temperature of the water may be high resulting in stress to the stocked fish. These aspects should be taken care of while stocking ponds with spawn, fry or fingerlings.