Tuesday, September 17, 2019 Information Gateway on Agriculture to Convert "Know How To Do How" മലയാളം
Fisheries > Culture Fisheries > Seafishes >Milkfish

Pond Management

Farming in earthen ponds

The ponds where milkfish fingerlings are reared are called “production ponds” or “rearing ponds”. The production pond ranges from 0.5 ha to 3 ha in area and are rectangular in shape, with water depth ranging from 0.3 to 0.7 m. The best bottom for these ponds is a soft, jelly like, colloidal and biologically active mud containing about 4% humus and large amounts of clay. The silt, sand and clay should be in the proportion of 64%, 32% and 4%. In Taiwan, a system of canals is provided on the outer boundary of the ponds to give protection to fish against extreme conditions of temperature.

About two months prior to stocking, the pond management begins for augmenting the growth of blue-green algae in pond bottom. These are similar to those practiced in nursery pond viz., draining of the water, drying, tilling, leveling and raking. Manuring of the ponds is always carried out. Usually, green manure is used, such as leaves and twigs of mangrove plants, rice straw, copra, rice bran, oilcakes, pig manure, chicken manure etc. The rate of fertilization usually varies from 500 to 2,000 kg/ha. Beside organic manure, inorganic fertilizers containing nitrates, phosphates and potassium (NPK) such as superphosphates, triple superphosphates, urea etc may also be applied at required rates. Water is then let into the pond and the depth is increased to about 30 cm gradually. Within two weeks the algal-periphyton complex (Lab-lab) develops at the pond bottom. Stocking in earthen pond follows only after the growth of Lab-lab. Usually fingerlings of 7 to 15 cm length are stocked at a rate of 2,000 to 10,000 per ha. When the growth of Lab-lab in the pond decreases, fresh dosages of manure are added.

Farming in pens

Inexpensive pen structures for farming the milkfish are constructed in shallow natural creeks, swamps, lagoons, lakes and bays, ranging in depth from 1 to 3 m. The bottom in pen culture sites should be of firm clay or mud so that poles and posts can be driven sufficiently deep to make them support the pen structure. Traditionally pens are made up of wooden planks, split bamboo etc. But in recent times, nets materials made of synthetic materials such as nylon, polypropylene, polythene etc are used commonly. A part of the vertical net barrier is buried inside the mud or ground with the aid of a footrope and small weights, secured to a chain link between concrete sinkers. At the upper level, floats are provided. Fingerlings stocked in usually feed upon the natural food in the lagoon or lake and no artificial food is provided.

pen

Pen culture of milkfish

Eradication of predators and pests

Certain predatory fishes, crabs, water snakes are the common threat to milkfish culture ponds and pen structures. These can be prevented from entering the farming area through use of fine meshed screens. Apart from these larvae of certain insects also pose threat to fingerlings of milkfish. Application of 0.5 ppm Baluscide, lime, urea etc. in the initial preparation of the ponds helps to reduce their growth.

Harvesting

 Milkfish has a higher growth rate in its first year in brackishwater, during when it grows to a marketable size of 30-45 cm long and 300-800 gm in weight. The periodicity of harvesting depends upon the number of batches stocked. During harvesting the pond is drained using pumps, while in the case of pens, the lowest tidal period is the best time for harvest. If trenches were provided in culture ponds, it would be easier to gather all the fish inside the trenches by draining the water and then capturing them. Usually, seine nets are operated for capturing farmed fish. The survival rates ranges from 80 to 95% amounting to a production ranging from 500 to 1000 kg/ha in ponds and 250 to 500 kg/ha in pens.

Top

Admin Login

Copyright © 2019. Developed & Maintained by Centre for E-Learning, Kerala Agricultural University