Pisiculture involves the following steps.

Collection of eggs:

Required types of fish eggs are collected during mon­soon months from rivers or other bodies of water. The eggs are collected twelve to fourteen hours after fertilization and made to hatch under pro­tected conditions. For the purpose of collection of eggs mosquito net are other types of suitable net may be used.

Collection of seeds:

ADVERTISEMENTS:

Fish seed means collection of young ones from the breeding ponds or from natural sources. The fish seeds are of two types fries and fingerlings. Fries are just hatched fishes while fingerlings are little older than fries. In our country a large number of collection stations have been established near the banks of Ganga, Yamuna etc. Hatching pits: The fertilized eggs are released into small pits located very close to the breeding ground.

These pits are specially made to promote the hatching of the eggs. The convenient size of a hatching pit is 8’X4’X2′. Usually a series of hatching pits are established with interconnections so as to allow the free flow of water from one pit to another. Hatching pits are of two types. Hatcheries and hatching hapas. Hatcher­ies are small sized pits into which fertilized eggs are transferred. Hatcher­ies have some drawbacks such as vagaries of temperature, attack by fish predators and drying up of the pit etc.

Hatching hapas is an improved method when compared to hatcheries. These are rectangular troughs made of a very coarse cloth of three layers. The outermost layer is made of a cheap coarse cloth. The middle layer of the tank is somewhat smaller and is made up of a round meshed mosquito net. The inner most cloth tank is still smaller in size.

In some parts of India, Hatcheries are made of cement and consist of two walls.

ADVERTISEMENTS:

Hapas have an advantage over plain hatcheries as they are generally pro­tected from predators and are not-subject to vagaries of temperatures. Transport of fries to cultured ponds. The fish fries are collected from hatcheries and transferred to large culture ponds. The fish hatchery is not a place for the complete growth of fish as its area is small. It is mainly meant to produce fish seeds. These seeds should be transported to larger ponds. These ponds ape of three types. Nursery ponds, rearing ponds and stocking ponds.

Nursery pond: The fries which are transported to nursery ponds are very fragile and they should be carefully maintained. As there is a possibility of high rate of mortality during transport it is advisable to have nursery ponds as close as possible to hatcheries.

The nursery pond is a shallow water reservoir ranging in depth from 3 to 8 feet. The extent of a nursery pond may vary from 2000 Sq feet to about

half an acre. A very vast nursery pond is not recommended as it will not be possible to control the conditions necessary for fish culture. The nursery pond generally has less natural food and it should be augmented by adding food and promoting development of natural food for fish.

ADVERTISEMENTS:

For this purpose chemical fertilizers should be added to the water which will promote the growth of zooplanktons and phytoplanktons. By the use of these manures it has been seen that the pond water will be full of tiny aquatic life within a matter of 10 to 15 days. When once the natural food is available in nursery ponds, the fries of fish can feed on them comfort­ably.

One of the important precautions to be taken in a nursery pond is to pre­vent the presence of predators which will create havoc to the fish culture. Another care to be taken is not to allow excess growth of planktons which may decrease the oxygen content of water.

After the fish fries are grown to about 10 to 15 cms they are transferred to another type of a pond called rearing pond which is necessary for their further growth.

Rearing ponds: After the fish fries have grown to a sufficient size, they should be transferred to larger ponds for two reasons. 1. As the size of the fish increases they should have free mobility in water without hindrance. 2. Large bodies of water like the rearing pond will have higher quantity of food resources which is necessary for fish.

ADVERTISEMENTS:

Generally the rearing ponds are much larger than nursery ponds (not nec­essarily in depth). They are usually narrower and longer to allow the fish to swim for long distances. Paddy fields having a depth of water, up to 2 or 3 feet may be an ideal rearing pond. The depth of the water in any case should not be more than six feet.

The water of rearing pond is usually seasonal and it should retain water for at least two or three months. The rearing pond, even though it may be a seasonal body of water, should be prepared properly before the fries are transferred. The preparation in­cludes removal of extra weeds, eliminating the predators, manuring the ponds to facilitate the growth of suitable planktons etc. The fish fries are usually transferred by collecting them in nets and trans­porting them into metal containers. In rearing ponds the fish reach a maxi­mum size of about 20 cms when they should be transferred to the stocking ponds for further growth.

Stocking ponds: The fingerlings that have reached the maximum size in rearing ponds are transferred to stocking ponds in containers of 1000 liter capacity. These containers are specially made to prevent injury to young fish. These containers should have facility for aeration. In some instances, in order to prevent excessive movement of the fish, mild sedatives are also used.

Before transportation, the fingerlings should be carefully washed by using medicated water (such as antibiotics, potassium permanganate) in order to prevent the spread of any possible diseases that the fish might have super­ficially contacted when they are in rearing ponds. One of the fungi, Saprolegnia parasitica is known to create havoc in fish hatcheries as it can kill the entire stock due to infection.

ADVERTISEMENTS:

The stocking ponds are usually large perennial ponds covering an area ranging from 2 to 20 hectares with an average depth of about 6 feet. Some precautions have to be taken to prepare the stocking ponds before the fingerlings are released into them. The process of preparing is same as that followed for rearing ponds. Preferably all predators must be elimi­nated even though it is difficult as the stocking pond is very wide and deep also. A

s increased quantity of food is required because the fish are in a rapid stage of growth, measures are to be taken to promote the growth of natural food for fish. Manuring is an important step to promote the growth of natural food. Organic manuring to the extent of 20,000 to 25,000 Kgs. of cow dung per hectare per year is essential for the proper growth of planktons. Chemical fertilizers such as super phosphate, ammonium ni­trate and ammonium sulphate at the rate of 1000 to 1500 Kgs. per hectare per year should also be used.

In addition to this, artificial food like pow­dered rice, oil cakes, mustard seeds, groundnut powder, etc., may also be added to argument the food resources. The artificial food should not be added in large quantities at a time. Small quantities of this are to be added daily, preferably in the morning hours.

The carrying capacity of the stocking pond depends on several factors like the type of fish, availability of food, oxygen content etc. It has been seen that a mixture of different species of fish(polyculture) in a stocking pond would have a higher yield when compared with a single species (monoculture). No fixed ratio of different species of fish in a polyculture has been evolved as yet. But experiments have shown that a combination of catla, rohu and mrigala in the ratio of 3:3:4 would yield best result. On an average polyculture of above species would yield be­tween 1000 to 1500 pounds per acre.