Fish spawn rearing techniques – rearing ponds

After stocking- attain a length of 20-25mm in 15 Artificial feeding-less than 10 % to as high as 95-100% The rearing ponds - second phase of carp culture fry to fingerlings- rearing ponds The rearing period - 2 and 3 months Figure: A series of rearing ponds Figure: A haul of carp fingerlings from a rearing pond

The management includes : removal of weeds by manual/mechanical method (ii) eradication of predatory and weed fishes by netting and/or poisoning (iii) manuring with organic and inorganic fertilizers, iv) stocking with carp fry in suitable combinations and ratios, (v) supplementary feeding (vi) Harvesting

The experiments conducted by CIFRI in various combinations of IMC and exotic carps, showed average survival of 76.6% (range 53.5 to 97.4%) The species combination -catla, rohu, mrigal and common carp; silver carp and grass carp; silver carp, grass carp and common carp Rate of stocking - 62,500 and 1,25,000 fry/ha, the number of fingerlings harvested ranges between 33,425 and 95,900/ha The production value- 1,505-3,486 kg/ha (av. 2,204 kg/ha) per 3 months.

The CIFRI – after 6-month rearing - survival rates of 62. 1- 98 The CIFRI – after 6-month rearing - survival rates of 62.1- 98.0% (av 78.2%) and gross production values 755-2,462 kg (av. 1,712 kg/ha/6 months) Here, fry of grass carp, silver carp and common carp were stocked at 0.1-0.25 million/ha in the ratio of 4:3:3 The survival - silver carp -99%, grass carp - 80-98% Zooplankton - most preferred food of catla fry The fry of rohu and mrigal accept other feeds, with silk worm pupae mustard/groundnut oil cake/rice bran/wheat bran/soybean/prawn waste Advanced fry of catla (35mm/2.2g) and rohu (45mm/2.9g) recorded high survival of 84.4 and 96.6% and a growth of 90mm (7.0g) and 117mm (14.7g), respectively, in 32 days

Rearing carp seed in pens/cages cage and pen systems For rearing larvae, fry and fingerlings Cages and pens - abundant supply of oxygen, flushing of metabolic wastes of the stocked fish, and nutrients from the catchment area In India, rearing of major carp seed in pens - Bhavanisagar and the Tungabhadra reservoirs

Rearing of carp seed in pens erected in the Tungabhadra reservoir Rearing of larvae in pens in Tungabhadra Board - one of the best managed and largest fish seed farms in south India The main objective -nurse the delicate carp spawn in pens up to fingerling stage and then stock them in the same reservoir in order to improve the fish landings and boost the socio-economic status of fisher folk It produced 24 t in 1954-55 and 4,200 t in 1981-82 : mainly catfishes, minor carps, minnows, etc.

An ideal site for pen erection - gentle slope with red loamy soil where water remains for a period of 2-3 months between August and November protected from wind and wave action A pen is normally made up of casuarinas poles, 2 m high, fixed at intervals of about 1.2 m, enclosing an area of 2,000 to 5,000 m2 Between the vertical poles, three horizontal rows of spilt bamboo stripes are tied to give support for the net materials

Close mesh (monofilament nylon fabric, 30 mesh) having a width of 1 Close mesh (monofilament nylon fabric, 30 mesh) having a width of 1.5 m is used as the pen wall material The bottom of the nylon fabric is inserted firmly into the mud and the vertical part securely tied to the poles and bamboo stripes After establishment of pen, the enclosure is limed, fertilized with cattle dung and treated with soap-oil emulsion The water in the pen is about 1.0-1.2m deep.

The pen - stocked with three-day-old major carp larvae (4-5 million/ha), fed with a mixture of groundnut oil cake and rice bran at a ratio of 1:1, from a boat Pens are periodically manured with organic and inorganic fertilizers to sustain production of zooplankton 10,000 kg cow dung, 400kg urea and 100 kg superphosphate per ha, followed by repeated applications, at 10% of these rates, every two or four weeks

Survival to 70-80 mm fingerlings is as high as 60% after three to four months Fishing licenses are given to local residents to uplift their socio-economic status Advantages of pen:easy, easy, less expensive and efficient for the nursery rearing of carp fry Drawback: the shortage of foreshore area for large-scale pen operation.