Trout farming in HP

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.  Recent find­ings indicate that 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 15^oC.  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 18^oC, but it has been found to tolerate the water temper­ature upto 25^oC in the region without any mortality.   However, the maximum growth is obtained within the temperature range of 10 to 18^oC.

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 20^oC, 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 18^oC, the recommended feed should be reduced to just half of the required amount and above 20^oC, 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 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 10-12^oC, feeding schedule of 6% is optimum but when it increases to 15^oC, the feeding schedule to be lowered to 4% and beyond 19^oC, 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.

Hygiene

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.

Source : Himachal Pradesh Agricultural University, Palampur