Freshwater aquaculture (2+1)

Unit 4 - Cultivable fish and their culture methods

4.1.3. Production of carp fingerlings

• Though a crucial phase for production of good quality seed of carps, this stage is often ignored due to paucity of space. Farmers often stock the grow – out ponds with fry resulting in poor survival.
• Ponds of size 500-2000 m2 are generally used for rearing carp fry to fingerling stage.
• The control of aquatic insects is not necessary in rearing ponds, but control of weeds, predators and weed fish is necessary in undrainable ponds. The pond preparation steps are similar to those of necessary ponds.

Pond fertilization
Ponds are manured with cow dung @ 3-4 tons/ha as basal dose 7-10 days before stocking and one week after liming at a dose of 200-500kg/ha. Thereafter cow dung is applied @ 500 kg/ha every fortnight. When poultry manure is use half the dosage of cow dung is used.
Additionally urea and single super phosphate @ 10 and 15 kg/ha are used for sustaining plankton growth.

Stocking
Fry (25mm) are transferred from nursery to rearing ponds, during cool hours. Either monoculture or polyculture is followed. Recommended combined stocking density is 2-3 lakh/ha

Supplementary feeding
Fry are fed @ of 8-10% of biomass for the first month, followed by 6-8 and 4-6% during the second and third month. The commonly used feed a mixture of rice bran and oil cakes particularly groundnut oil cake in the ratio of 1:1. Other ingredients such as fishmeal, soybean floor etc., can be incorporated for improving feed quality.

Post stocking pond management
Maintaining water level of 1.0 – 1.5m and intermittent fertilization as mentioned earlier are the other management measures required.

Harvesting
Fingerlings are harvested after 2-3 months at a size of 80-100 mm/ 8-10g. Survival rates of 70-80% can be obtained with good management measures.

Transportation of fry and fingerlings
Long distance transport of fry and fingerlings can be done by packing them in sealed polyethylene bags filled with water and pure oxygen in the ratio of 1:2 to 1:3 water to oxygen.
The number of seed per bag depends on the size of the seed and duration of transport.
Fry and fingerlings are conditioned by crowding them in hapas and starving the seed for 24-48 hours. They are then packed during cool hours in polythene bags with water and oxygen. The polyethylene bags are supported by suitable boxes/bags to prevent damage during transport. Ice can be added to bags to reduce temperature and metabolic rate of the fish.