Aquaculture has been identified as one of the integral component of the modern farming system all over the world for diversification of agricultural practices. The hill State Himachal Pradesh with its varied topography and diverse aquatic resources, has vast potential for culture fisheries under the different agro-climatic conditions. So far the concept of culture fisheries in the State is at its inception. The Department of Fisheries, College of Vety., & animal Sciences, Palampur is engaged in conducting the need based research on culture aspect of fishery. As such a polyculture fish model has been evolved for the agro-climatic environment of lower reaches of zone II and higher reaches of Zone I, particularly the prevailing conditions 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.
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.
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 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 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.
(iii) 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.
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 the State. Of these, mirror carp is a bottom feeder, grass carp is a macro-vegetation feeder and silver carp is surface feeder.
Selection of species ratio generally depends upon the local conditions, seed availability, nutrient status of pond, etc. The species ratio in the recommended model for Zone II is - 2 mirror carp : 2 grass carp : 1 silver carp.
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.
The level of natural food organisms in the fish culture ponds can not 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:
Ingredients (%) Qty
Fish meal 10 1.0 kg
Wheat bran 50 5,0 kg
Groundnut cake 38 3.8 kg
DCP 2 0.2 kg
Supplevit-M 0.5 0.05 kg
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 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.
Calender for fish farming
(i) Construction of tanks.
(ii) Renovation of Ponds/tank which includes desilting and repairing of old tanks.
February: Preparation of ponds
(i) Liming: General rate 250 kg/ha or 25 g/sq m of water area.
(ii) 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.
(iii) Fill the pond with water just after manuring and leave it for 12-15 days.
(iv) 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 of ponds
(i) 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.
(ii) Species to be stocked are common carp, grass carp and silver carps.
(iii)Species ratio- common carp 3:Grass carp 2: and silver carp 1.
(iv) 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.
(v) Stocking upto 15th March.
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 15th 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.
Harvesting of table fish can be started w.e.f.15th 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.
Zone II and III of Himachal Pradesh have vast potentials for the culture of highly prized fish “Rainbow Trout”. The agroclimatic conditions of the area under these two zones are very congenial for cold water aquaculture. The Deptt. of Fisheries COVAS, HPKV, Palampur has successfully reared the Rainbow trout fingerlings for table purposes at campus fish farm, Palampur. As such the conventional practice of culturing Rainbow trout in the high hills only is no more tenable in the light of recent findings. However, more tenable recent findings included trout can be cultured at lower elevation even upto 1000 m msl, provided the optimum water quality and quantity is ensured.
Selection of site
For trout culture, such a site should be selected where the quality and quantity of water is available through perennial source like spring, river, etc.
Construction of ponds
The cemented ponds/ raceways are required for the culture of trout fish. The rectangular tanks are better than the circular cisterns. The economical size of a trout race way should be 12-15 m x 2-3 ms x1.2 -.5 m with an inlet and an outlet for overflow of water fixed with wire mesh screws to prevent the exit of stocked species. There should be a drain pipe at the bottom of the pond to facilitate the harvesting as well as the cleaning of tank from time to time.
Water supply in the farm
The water supply in trout farm should be through a filter bed/sedimentation tank. There is a lot of silt problem in this area particularly during monsoon season when the water is turbid which is not good for trout farming. The quantity of water required for a trout farm is related with the stocking density, size of fish as well as the water temperature. Therefore, it is necessary to regulate the flow of water very carefully. For example, 30,000 fries need water flow of about 15 L/minute, the fish below 250 g needs a water flow of 0.5 L/kg/minute at 10-12 oC. The water flow of above mentioned economical size of tank should be 52 m3/hour for stocking of fingerlings of 5-50 g at 15oC. Thus, the water flow is regulated in such a way that fishes should not assemble at one place and also do not move fast. The flow of water should be increased with the increase of water temperature.
Physico-chemical parameters required for a trout farm:
The physico-chemical parameters responsible for the successful culture of trout are temperature, dissolved oxygen, pH and turbidity.
Temperature: The fish thrives well within the temperature range of 5 to 18oC, but it has been found to tolerate the water temperature upto 25oC in the region without any mortality. However, the maximum growth is obtained within the temperature range of 10 to 18oC.
Dissolved oxygen: The oxygen concentration range is from 5.8 to 9.5 mg/L. If the oxygen concentration is 5 mg/L, it is better to increase the flow of water.
pH: A neutral or slightly alkaline pH is best for the trout. The tolerable minimum and maximum pH values are 4.5 and 9.2, respectively. However, pH range is ideal for the growth of this fish.
Turbidity: The crystal clear water is required and there should not be any contamination. The turbidity should not be more than 25 cm.
Stocking density: It is related with the water supply, water temperature, quality/water and types of feed. If water temperature is above 20oC, the stocking density should be less than the recommended density. The fry fingerlings (5 to 50 g) is stocked at the rate of 20 kg fish per cubic meter of water surface area.
Supply of feed: The quantity of feed mainly depends on the water temperature and size of fish. If the water temperature is above 18oC, the recommended feed should be reduced to just half of the required amount and above 20oC, better to stop the feeding. The feeding should also be suspended on a cloudy day and when the water is turbid.
A practical feed formula that is in practice at Fish Farm, CSKHPKV, Palampur, is given below :
Feeding @ 4-6 % is necessary for the fingerlings for better growth but due consideration should also be given to the water temperature for following the feeding schedule. At the water temperature range of 10-12oC, feeding schedule of 6% is optimum but when it increases to 15oC, the feeding schedule to be lowered to 4% and beyond 19oC, it should be just 50% of the optimum schedule. The optimum growth rate per month is 80 g.
Table size fish
The fish after gaining the weight of 250 g is advisable to be harvested because beyond this size the growth is slow and rearing is uneconomical.
The cleanliness is a very important factor in trout farming. The trout should be cleaned and disinfected either with 10% formaline or 4 ppm KMno4 solution periodically. The infected fish should be immediately removed from the tank and due care should be taken to consult some fishery expert regarding the disease, if any.