Aquaculture in Hills

The pre-requisite for the fish farm­ing is the availability of perennial water. As such the fish farming in the hilly region may be practiced in the watershed areas, along the streams and river banks or any place where the water supply is assured either by irrigational channel or lift irrigation scheme.

A polyculture fish model has been evolved for the agro-climatic environment, like that of Palampur valley in Distt. Kangra.  In this model, 3 species of exotic carps (Grass carp, Silver carp, Mirror carp) have been recommended to the farmers which is based on their growth performance, adaptability and other eco-biological parameters that have been inves­tigated thoroughly.

Selection of site

For fish culture such a site should be selected where the water is available through a regular source like spring, river, channel, etc. or even water­logged land may be reclaimed for this purpose.  The soil should not be completely sandy but should be a mixture of sand and clay so that it has the capacity of retain­ing the water.  Alkaline soils are always better for good growth of fish.  Before construction of pond, the physico-chemical properties of soil should be tested.

Construction of ponds

The size and shape of the pond depends upon the availability of land and type of production.  For an economically viable project, the minimum size of pond should not be less than 300 sq.m and1.5 m deep.  A typical pond should have an inlet for the entry of water fixed with wire mesh so as to prevent the entry of unwanted indigenous fauna and an outlet for overflow of excess water fixed with wire mesh to prevent the exit of stocked spe­cies.  There should be a drain pipe at the bottom of pond and a harvesting pit to facilitate the harvesting and to dry the pond from time to time.  The sides or dykes of the pond should be well compacted, sloppy and planted with grasses or herbs to protect them from erosion.  The gullies and watershed area can also be converted into pond by raising an earthen dam.

Preparation of ponds

• Liming: Liming of the pond is necessary to eradicate the harmful insects, micro-organisms, to render soil alkaline and provide calcium to the growing fish.  If soil is not acidic, the lime can be used at the rate of 25 g per sq m and if soil is acidic increase the quantity of lime by 50%.  After broadcasting of lime in whole tank, it must be left dry for 4 days to one week.
• Manuring: Manuring is done with the objective to increase the plankton biomass, which form the natural food of the fish.  The rate of manure depends on the fertility status of soil.  The organic manure such as cow dung is used @ 20 tones/ha i.e. 2 kg per sq. m area in the mid hill region.  Initial manuring is to be done with 50% of total required manure and subsequently the rest 50% should be used in the equal monthly installments.  Fill the tank with water just after manuring and leave it for 12-15 days.
• Control of aquatic weeds and predators: The algal blooms are sudden out-bursts due to higher manuring or organic effluent.  These blooms liberate good amount of carbon dioxide leading to oxygen depletion, which can cause large-scale mortality.  If reddish scum appears on the surface of the water, this means the outbreak of algal bloom.  The manuring and artificial feeding should be stopped immediately and allow fresh water in the pond.  If the algal blooms are in excess, spray 3% copper sulphate solution selectively to worst affected areas of pond or superphosphate at the rate of 1 g/m water area.  The eradication of weed and predatory fishes is necessary to avoid competition with cultivable fishes for space and food.  These fishes may be eradicated either by repeated netting or draining the water or poisoning the pond.  Generally used poisons for this purpose are mahua oilcake (200 ppm), 1% tea seedcake or turpentine oil @ 250 l/ha.  The other chemicals such as Aldrin (0.2 ppm) and Endrin (0.01 ppm) can also be used but should be avoided. In case of the use of these chemicals, the stocking of fish seed (fry/fingerlings) may be delayed at least by 10 to 25 days so as to facilitate elimination of the chemicals/residues.
• Stocking: Judicious selection of compatible fast growing species is of vital importance in maximizing fish production.  A combination of three species viz. mirror carp, grass carp and silver carp fulfills the species selection requirements and this model has proven to be the ideal combination for sub-temperate region.. Of these, mirror carp is a bottom feeder, grass carp is a macro-vegetation feeder and silver carp is surface feeder.
• Species ratio: Selection of species ratio generally depends upon the local conditions, seed availability, nutrient status of pond, etc. The species ratio in the recommended model is - 2 mirror carp: 2 grass carp: 1 silver carp.
• Stocking details: Rate of stocking usually depends on the fertility of the pond and the measures adopted to increase its biological productivity by manuring, artificial feeding, monitoring of growth and maintaining good health of fish. The rate of stocking recommended for this zone is 15,000 fingerlings per ha. With artificial feeding. It is good to stock the ponds with fingerlings of 40-60 mm size for better survival and higher production. It is better to stock the pond after 15 days of manuring in early hours of day or in the evening. The cloudy day or warmer part of day is to be avoided for stocking.
• Supplementary feeding: The level of natural food organisms in the fish culture ponds cannot be maintained to the required extent even after manuring. Hence, supplementary feeding with diet rich in protein, carbohydrates and fats is essential for higher rate of fish growth. The ingredients generally used for artificial feeding are groundnut oil cake and wheat bran in the ratio of 1:1. Feed should be preferably provided in the form of pellets or bowls @ 2% of the total biomass and feed them by hand at different places in the ponds so that all the fishes must get uniform quantity of feed for their uniform growth. Grass carps are to be fed with chopped succulent grass or discarded vegetable leaves. Kitchen refuse can also be used as supplementary feed for fish culture.

A practical feed formula which is in practice at Fish Farm, CSKHPKV is given below:

For preparing 10 kg feed:

Supplementary feeding @ 2-3% is necessary for better yield per unit area since the natural productivity of water in this zone is very less.

Monitoring of growth

Besides nutrients, the abiotic factors like temperature, salinity and photoperiod influence the growth of the fish.  After 2 months of stocking, the 20% of the stock should be harvested so as to evaluate the growth per month as well as to calculate the correct amount of feed to be supplied daily.  Later on, this practice is to be repeated every month till the fish stops artificial feed­ing.  Based on research data generated at Fish Farm HPKV, Palampur, it is seen that the fishes attain their growth during 8 productive months (i.e. middle of March to middle of November) under the existing climatic conditions.  During four winter months (i.e. middle of November to middle of March), there is no growth.  As such the supplementary feed is to be given during the eight productive months.  The results in terms of production efficiency of afore­said model is computed as high as 5 tones per ha per year.

Harvesting

Harvesting is conveniently done either by drag netting or by cast netting (useful for small ponds) or by draining the pond.  Supplementary feeding is stopped a day before the date of harvesting.  Har­vesting is done during cool morning hours as per the demand of market.  For this region, the best time of harvesting is December and January which are non-produc­tive months for fish farming.  The prefera­ble time of stocking is mid of March or first week of April.  In this way the four non-productive winter months can be uti­lised for the renovation, desilting and preparation of ponds.

Calendar for fish farming

January:

• Construction of tanks.
• Renovation of Ponds/tank which in­cludes desilting and repairing of old tanks.

February: Preparation of ponds

• Liming:  General rate 250 kg/ha or 25 g/sq m of water area.
• Manuring:  After a week of liming, manuring should be done @ 20 tones/ha.  Initially half of the total quantity and subsequently rest half in equal monthly installments.  For example 1 hectare area (10000 sq. m.) the total amount of manure required is 2000 kg i.e.  1000 kg to be applied in the beginning and rest to be applied @ 145 kg per month from March to October.
• Fill the pond with water just after manuring and leave it for 12-15 days.
• In case of old ponds, the unwanted weed fish, predatory fish and harmful in­sects etc. to be eradicated either manually or by poisoning the water.

March to November:

• Stocking should be done after 15 days of manuring when watercolour is green, which is indicative of the presence of natural food in water.  The cloudy day or warmer part of the day is to be avoided for stock­ing.
• Species to be stocked are common carp, grass carp and silver carps.
• Species ratio- common carp 3:Grass carp 2: and silver carp 1.
• Stocking rate - 15,000 finger­lings/ha.  For example 0.1 ha tank is to be stocked with 1500 fingerlings, in the ratio of 750 common carp : 500 grass carp : 250 silver carp.
• Stocking upto 15th March.

Stocking of ponds

• Stocking should be done after 15 days of manuring when watercolour is green, which is indicative of the presence of natural food in water.The cloudy day or warmer part of the day is to be avoided for stocking.
• Species to be stocked are common carp, grass carp and silver carps.
• Species ratio- common carp 3:Grass carp 2: and silver carp 1.
• Stocking rate - 15,000 finger­lings/ha.  For example 0.1 ha tank is to be stocked with 1500 fingerlings, in the ratio of 750 common carp : 500 grass carp : 250 silver carp.
• Stocking upto 15^th March.

Feeding: Feeding should be started after two days of stocking, at the rate of 3% of total biomass of fish seed stocked, during first month i.e up to 15^th of Aporil. Subsequently the feeding rate should be reduced to 2%. The chopped succulent grass should also be supplied to feed the grass carp at lib. The feeding is to be done thrice daily. December: Harvesting of table fish can be started w.e.f.15^th of November on wards as per the demand. There is no need of harvesting the entire stock at a time, this may be prolonged during the three winter months as per the demand so as to get good price.

Source : Himachal Pradesh Agricultural University, Palampur