Finfish Breeding and Hatchery Management

Unit 5 - Fish seed rearing techniques

5.2.3. Rearing of carp seed in pens erected in the Tungabhadra reservoir

• Rearing of larvae in pens made from locally Tungabhadra Board which has one of the best managed and largest fish seed farms in south India. In the early 1980s, initial trials were made to establish pens in the periphery of the reservoir.
• The main objective was to 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.
• Since then, the practice of raising carp spawn up to fingerlings has become well-established.
• The Tungabhadra reservoir has a maximum water area of 37,814 ha and offers vast scope for fish production. It produced 24 t in 1954-55 and 4,200 t in 1981-82 : mainly catfishes, minor carps, minnows, etc.
• With the release of pen-cultured carp fingerlings starting from 1982, the major carps, which were not formerly part of the catch, accounted for nearly 60% of the total catch in 1994.
• An ideal site for pen erection will generally have a gentle slope with red loamy soil where water remains for a period of 2-3 months between August and November.
  The site should be will protected from wind and wave action by small hillocks surrounding the area.
• 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 1.5 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.
• Pen preparation starts 15-20 days before the dam reaches its full level.
• 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 is then stocked with three-day-old major carp larvae (4-5 million/ha), produced in the adjacent fish seed farm, fed thereafter with a mixture of groundnut oil cake and rice bran at a ratio of 1:1, from a boat.
• In addition, the pens are periodically manured with organic and inorganic fertilizers to sustain production of zooplankton.
• There is a basal application of 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.
• Periodic sampling is done to monitor growth and adjust the feed quantity.
• The fingerlings thus grown are stocked in the same reservoirs to enhance major carp production.
• Fishing licenses are given to local residents to uplift their socio-economic status.
• Although the pen construction is simple, easy, easy, less expensive and efficient for the nursery rearing of carp fry, one drawback is the shortage of foreshore area for large-scale pen operation.