· It is the principal form of aquaculture that involves the breeding and taking care of fish for increasing their production.
· It was established in Nepal in 1957 A.D.
Scope of Fish Farming
· Fishes are easily available and can be cultured in many regions of Nepal.
· Many educated and uneducated people are involved in fish farming due to the following reasons:
(i) Fishes are a rich source of protein.
· The protein content of fish is comparatively higher than that of eggs or another animal source.
(ii) Byproduct of Fish
· The important byproducts of fish are:
(a) Fish Oil
· It is of two types: liver oil and body oil.
· Liver oil is used in making medicines. It is rich in vitamins A, D and B complex.
· Body oil is used in manufacturing soaps, paints, candles, varnishes etc.
(b) Fish Meal
· It is used mainly as feed for pigs and poultry.
(c) Manure
· Low-grade fish that are unfit for human consumption is used to prepare fish manure for the field.
(iii) Demand for fish is high due to the increased population, so it provides a good source of income.
(iv) Nepal has a high scope of riverine and pond fisheries development because of the richness of hill streams, lakes, ponds and rivers in different parts of the country.
(v) Raising desirable varieties of fishes in the ponds, lakes and rivers of Nepal can attract tourists. People enjoy fishing for sport (fish tourism).
(vi) The climate of our country is suitable for raising different types of local and improved breeds of fish.
(ii) Byproduct of Fish
· The important byproducts of fish are:
(a) Fish Oil
· It is of two types: liver oil and body oil.
· Liver oil is used in making medicines. It is rich in vitamins A, D and B complex.
· Body oil is used in manufacturing soaps, paints, candles, varnishes etc.
(b) Fish Meal
· It is used mainly as feed for pigs and poultry.
(c) Manure
· Low-grade fish that are unfit for human consumption is used to prepare fish manure for the field.
(iii) Demand for fish is high due to the increased population, so it provides a good source of income.
(iv) Nepal has a high scope of riverine and pond fisheries development because of the richness of hill streams, lakes, ponds and rivers in different parts of the country.
(v) Raising desirable varieties of fishes in the ponds, lakes and rivers of Nepal can attract tourists. People enjoy fishing for sport (fish tourism).
(vi) The climate of our country is suitable for raising different types of local and improved breeds of fish.
(vii) Fish farming provides full-time employment for millions of people.
(viii) It can be done in small spaces, paddy fields and ponds. Many small ponds and lakes in our country can be used to culture or rear fish.
B. Exotic fishes
· The fishes imported into a country for fish culture are called exotic fishes. Six species of fish of commercial value have been imported into Nepal.
· It is the culture of only a single type of fish species in a pond.
· In monoculture, fishes can be of different ages and life stages or they can be separated in different ponds.
(ii) Polyculture
· It is the culture of two or more species of fishes together in a pond.
· Fingerlings of fast-growing stages of compatible fishes, with different feeding habits are selected and stocked together.
· For example, the culture of Chinese, grass and big-head carps as silver carp eats phytoplanktons, grass carp pond vegetation and big-head carp zooplanktons.
Paddy Cum Fish Culture
· This culture of fish in paddy fields is being practised in Terai and some parts of the valley.
· It is the double cropping system in which fish are reared and paddy are grown at the same time in the same field.
(ii) Induced Breeding (Artificial Fertilization)
· It is the technique used for the purpose of inducing breeding in fishes.
· In this technique, sexually mature males and females are induced to spawn in confined water at the desired time by injecting them with pituitary extract.
· The sperms from males and ova from females are collected and mixed thoroughly. The eggs will be fertilized within half an hour.
· Now, these fertilized eggs should be transferred into the hatching pit.
Nursery Pond
· It should be made 2 months before the transfer of hatchlings (fish fries).
Rearing Pond
· In this pond, fish fries are developed into fingerlings.
· It is larger than the nursery pond due to the greater size of fingerlings than fries. Depth should not exceed more than 1.5 m.
· Pond should be well shaded and fenced.
· Fingerlings must be provided with more nutritious artificial food besides natural foods of the pond.
· After 2–3 months, fingerlings reach up to 75–125 mm.
· Pond should be manured periodically for the rich growth of phytoplankton and zooplankton.
· The well-fed fingerlings are transferred into a stocking pond after 3 months.
Stocking Pond
· It is larger than a rearing pond with a depth of 6 ft. A tank of 100 ft (length), 100 ft (broad) and 10 ft (depth) is considered as an ideal to give support for 4,000 fingerlings.
· Fingerlings grow here for about 2–3 years. It should be well managed before the release of fingerlings into it.
· PH should be maintained.
· Filamentous plants like Spirogyra, Ulothrix and other phytoplanktons should be introduced and grown to increase dissolved O2 concentration.
· Tank should be well manured and well protected from predators.
Harvesting
· It is the collection of fishes. It is done by experts by the 2nd or 3rd year of stocking.
Marketing
· The harvested fishes are stored in a cold store temporarily and supplied to markets by vehicles usually keeping fish inside ice packed baskets.
Selection of Fishes
· For profitable fish farming, it is necessary to select such species of fish that fulfil the following conditions:
i. It should have a fast growth rate.
ii. It should be able to utilize both the natural and artificial food of the pond to the maximum extent.
iii. It should be hardy and resistant to diseases.
iv. It should be able to survive even in low dissolved oxygen concentration.
v. It must be a prolific breeder and easy to breed in ponds.
vi. It should be predaceous and preferably herbivorous in habit.
vii. It should be tasteful and of high nutrient and market value.
Pond Management
· The following physicochemical constituents of the pond water should be considered during pond management for better production of the fish.
(i) Soil
· The soil should not be porous. The clay loam with deep stratification is used for the control of soil leakage.
(ii) Water
· Water source for the pond should be permanent i.e. from spring, river or irrigation.
(iii) PH
· Optimum pH is 7–8 but pH 5–10 is tolerable.
· Fishes prefer neutral or alkaline water.
· If the water becomes acidic, the lime should be added to increase pH.
(iv) Oxygen
· The concentration of oxygen in water increases due to phytoplanktons or other plants.
· Constant flow of water is the best measure for the oxygen balance in a pond.
· Surface swimming fishes take atmospheric oxygen.
· Some amount of CO2 should be retained in the water for the photosynthetic activity and retention of calcium in the water.
(v) Light
· Fish pond must be at a sunny place for the photosynthetic activity of phytoplankton.
· Light affects the activity of the fries, temperature of the water and growth of other plants.
(vi) Temperature
· Optimum temperature of pond water for the common carps is 20°–30°C.
· Decrease and increase in temperature below and above the optimum level have address effects.
(vii) Turbidity
· It is caused due to dust particles, clay or silt or others.
· Turbidity plays an important role in the productivity of fishes by controlling over other physical factors (light, temperature) etc. So, pond water must not be turbid at all.
(viii) Fencing
· Pond must be well protected against snakes, local carnivorous fishes (Channa, Wallago etc) and other predators.
(ix) Manuring
· Less productive soil needs manuring with cow dung, compost and chemical fertilizers.
· Excessive manuring changes pH of the water and other chemicals to reduce phytoplanktons or other aquatic weeds. Excess nitrogenous fertilizers increase NH4+ ions which may act as nerve poisons to fishes.
(viii) It can be done in small spaces, paddy fields and ponds. Many small ponds and lakes in our country can be used to culture or rear fish.
Fish Farming in Nepal
· There are 185 species of fish in Nepal found in various water bodies.
· There are 185 species of fish in Nepal found in various water bodies.
| Indigenous Species | Exotic Fishes | |
|---|---|---|
| Labeo rohita (Bohu) Catla catla (Bhakur) Cirrhina mrigala (Naini) Schizothorax spp. (Asala) Neolissochilus hexagonolepis (Katle) Tor spp. (Mahaseer) Wallago attu (Buhari) Rita rita (Rita) Heteropneustes fossilis (Singhi) Clarias batrachus (Magur) Channa punctatus (Hile) Notopterus chitala (Mohi) |
Cyprinus carpio (Common carp) Ctenopharyngodon idella (Grass carp) Hypopthalmicthys molitrix (Silver carp) Aristichthys nobilis (Bighead Carp) |
Warm-water species |
| Onchorhynchus mykis (Rainbow trout) Salmo trutta (Brown trout) |
Cold water-species |
A. Indigenous Species
· The fish species which are native to our country or found in Nepal are called indigenous species.
· The fish species which are native to our country or found in Nepal are called indigenous species.
· Some common indigenous fish species of Nepal are given in the above table.
B. Exotic fishes
· The fishes imported into a country for fish culture are called exotic fishes. Six species of fish of commercial value have been imported into Nepal.
· They are:
a. Warm Water Species
i. Cyprinus carpio (Common carp)
ii. Ctenopharyngodon idella (Grass carp)
iii. Hypopthalmicthys molitrix (Silver carp)- imported from Japan in 2025
iv. Aristichthys nobilis (Bighead Carp or Hungarian carp)- imported from Hungary in 2028
a. Warm Water Species
i. Cyprinus carpio (Common carp)
ii. Ctenopharyngodon idella (Grass carp)
iii. Hypopthalmicthys molitrix (Silver carp)- imported from Japan in 2025
iv. Aristichthys nobilis (Bighead Carp or Hungarian carp)- imported from Hungary in 2028
b. Coldwater Species
i. Onchorhynchus mykis (Rainbow trout)
ii. Salmo trutta (Brown trout)- reintroduced from Japan (1988)
· The warm-water species of exotic fishes are being cultured with 3 indigenous species (Rohu, Bhakur and Naini).
i. Onchorhynchus mykis (Rainbow trout)
ii. Salmo trutta (Brown trout)- reintroduced from Japan (1988)
· The warm-water species of exotic fishes are being cultured with 3 indigenous species (Rohu, Bhakur and Naini).
FISH CULTURE PRACTICES
(i) Monoculture· It is the culture of only a single type of fish species in a pond.
· In monoculture, fishes can be of different ages and life stages or they can be separated in different ponds.
(ii) Polyculture
· It is the culture of two or more species of fishes together in a pond.
· Fingerlings of fast-growing stages of compatible fishes, with different feeding habits are selected and stocked together.
· For example, the culture of Chinese, grass and big-head carps as silver carp eats phytoplanktons, grass carp pond vegetation and big-head carp zooplanktons.
Advantages
· All the available spaces are fully utilized.
· The fishes with different feeding habits utilize the food resources of the pond effectively.
· For example, Bhakur (surface feeder, feeds on zooplankton), Rohu (middle feeder, feeds on aquatic vegetation) and Naini (bottom feeder, feeds on the benthic organism and faecal matters) have different feeding habits and habitat.
· All the available spaces are fully utilized.
· The fishes with different feeding habits utilize the food resources of the pond effectively.
· For example, Bhakur (surface feeder, feeds on zooplankton), Rohu (middle feeder, feeds on aquatic vegetation) and Naini (bottom feeder, feeds on the benthic organism and faecal matters) have different feeding habits and habitat.
· They are grown together to fully occupy the space and utilize available food resources.
Paddy Cum Fish Culture
· This culture of fish in paddy fields is being practised in Terai and some parts of the valley.
· It is the double cropping system in which fish are reared and paddy are grown at the same time in the same field.
Cage fish culture
· The cages are placed in lakes, ponds, rivers, reservoirs to keep and protect the fishes until they are harvested.
· The cages may be stationary or floating.
· It is practised in Phewa, Rupa and Begnas lakes of Pokhara valley and Indrasarobar reservoir of Kulakhani.
· The cages are placed in lakes, ponds, rivers, reservoirs to keep and protect the fishes until they are harvested.
· The cages may be stationary or floating.
· It is practised in Phewa, Rupa and Begnas lakes of Pokhara valley and Indrasarobar reservoir of Kulakhani.
FISH FARMS IN NEPAL
At present, there are fourteen fish farms in Nepal.
| Tarahara Fishery Development Centre (Sunsari) Fatyapur Fishery Centre (Saptari) Janakpur Fishery Centre (Dhanusa) Parwanipur Fish Centre (Bara) Hetauda Occupational Fishery Centre (Makawanpur) Rapti Occupational Fishery Centre (Chitwan) Balaju Central Hatchery (Kathmandu) Godawari Fishery Centre (Lalitpur) Trishuli Fishery Centre (Nuwakot) Kulekhani Indrasarobar Fishery Centre (Makawanpur) Bhairahawa Fishery Development Centre (Rupandehi) Pokhara Fishery Centre (Kaski) Bardia Fishery Centre (Bardia) Dhangadhi Fishery Centre (Kailali) |
2017 2029 2019 2015 2024 2027 2027 2019 2028 2041 2018 2019 2045 (Newly proposed) 2032 |
Management of Fish Farming
· It consists of the construction of various ponds for various stages of development and the arrangement of various provisions.Collection of Eggs
· Eggs are collected by natural and induced breeding.
(i) Natural Breeding
a. During the rainy season (June–August), mature fishes migrate to adjoining land with shallow water. They are collected and allowed to mate and lay eggs. Eggs are fertilized within 14 hours.
b. Fertilized eggs are collected by a round meshed mosquito net of about 15' × 5' which is tied at the river bank by two bamboo poles.
c. Eggs are gathered at a place and lifted up periodically and are transferred to an earthen vessel kept floating nearly.
· Eggs are collected by natural and induced breeding.
(i) Natural Breeding
a. During the rainy season (June–August), mature fishes migrate to adjoining land with shallow water. They are collected and allowed to mate and lay eggs. Eggs are fertilized within 14 hours.
b. Fertilized eggs are collected by a round meshed mosquito net of about 15' × 5' which is tied at the river bank by two bamboo poles.
c. Eggs are gathered at a place and lifted up periodically and are transferred to an earthen vessel kept floating nearly.
(ii) Induced Breeding (Artificial Fertilization)
· It is the technique used for the purpose of inducing breeding in fishes.
· In this technique, sexually mature males and females are induced to spawn in confined water at the desired time by injecting them with pituitary extract.
· The sperms from males and ova from females are collected and mixed thoroughly. The eggs will be fertilized within half an hour.
· Now, these fertilized eggs should be transferred into the hatching pit.
Hatching Pits
· These are the series of tanks (pits) of 8' × 4' × 2', constructed near the breeding place for hatching the egg.
· These tanks are interconnected for easy flow of water from one tank to another in order to stimulate the eggs to grow.
· Each hatching pit consists of 3 tanks of different dimensions called hapa.
· The outermost is largest measuring 6' × 3' × 1.5' middle 5' × 2.5' × 1' and made up of round meshed mosquito net and innermost hapa is smallest (4' × 2' × 0.75') and is made up of simple cotton cloth.
· These are the series of tanks (pits) of 8' × 4' × 2', constructed near the breeding place for hatching the egg.
· These tanks are interconnected for easy flow of water from one tank to another in order to stimulate the eggs to grow.
· Each hatching pit consists of 3 tanks of different dimensions called hapa.
· The outermost is largest measuring 6' × 3' × 1.5' middle 5' × 2.5' × 1' and made up of round meshed mosquito net and innermost hapa is smallest (4' × 2' × 0.75') and is made up of simple cotton cloth.
Hatching of Eggs
· About 800,000 to 2,000,000 eggs are kept in the inner hapa of each pit for hatching. ·ut of them, only 5% to 25% of eggs are hatched within 8 to 16 hours.
· Newly hatched fries are active, small, slim and tender. They pass out from inner to ·uter hapa through the holes of meshes.
· Fish fries are kept here until they reach up to 5–6 mm and after that, they are transferred into a nursery pond.
· About 800,000 to 2,000,000 eggs are kept in the inner hapa of each pit for hatching. ·ut of them, only 5% to 25% of eggs are hatched within 8 to 16 hours.
· Newly hatched fries are active, small, slim and tender. They pass out from inner to ·uter hapa through the holes of meshes.
· Fish fries are kept here until they reach up to 5–6 mm and after that, they are transferred into a nursery pond.
Nursery Pond
· It should be made 2 months before the transfer of hatchlings (fish fries).
· It should be free from predators.
· Depth of pond must not exceed 1.2 m.
· Firstly, the water of the pond should be drained out and freshwater should be filled and if left undisturbed and unused for about 1 or 2 months, water becomes rich in zooplanktons as fish fries prefer zooplanktons.
· pH must be kept in between 8 and 9.
· In the case of decreased pH, liming is done. Mineral salts (Ca, Na, K, P) should be dissolved in water periodically.
· Depth of pond must not exceed 1.2 m.
· Firstly, the water of the pond should be drained out and freshwater should be filled and if left undisturbed and unused for about 1 or 2 months, water becomes rich in zooplanktons as fish fries prefer zooplanktons.
· pH must be kept in between 8 and 9.
· In the case of decreased pH, liming is done. Mineral salts (Ca, Na, K, P) should be dissolved in water periodically.
· Fish fries are transported in the water-filled earthen or metal vessel.
· Water should be kept clean by removing dead fries and other unwanted substances with the help of a small handled net.
Rearing Pond
· In this pond, fish fries are developed into fingerlings.
· It is larger than the nursery pond due to the greater size of fingerlings than fries. Depth should not exceed more than 1.5 m.
· Pond should be well shaded and fenced.
· Fingerlings must be provided with more nutritious artificial food besides natural foods of the pond.
· After 2–3 months, fingerlings reach up to 75–125 mm.
· Pond should be manured periodically for the rich growth of phytoplankton and zooplankton.
· The well-fed fingerlings are transferred into a stocking pond after 3 months.
Stocking Pond
· It is larger than a rearing pond with a depth of 6 ft. A tank of 100 ft (length), 100 ft (broad) and 10 ft (depth) is considered as an ideal to give support for 4,000 fingerlings.
· Fingerlings grow here for about 2–3 years. It should be well managed before the release of fingerlings into it.
· PH should be maintained.
· Filamentous plants like Spirogyra, Ulothrix and other phytoplanktons should be introduced and grown to increase dissolved O2 concentration.
· Tank should be well manured and well protected from predators.
Harvesting
· It is the collection of fishes. It is done by experts by the 2nd or 3rd year of stocking.
Marketing
· The harvested fishes are stored in a cold store temporarily and supplied to markets by vehicles usually keeping fish inside ice packed baskets.
Selection of Fishes
· For profitable fish farming, it is necessary to select such species of fish that fulfil the following conditions:
i. It should have a fast growth rate.
ii. It should be able to utilize both the natural and artificial food of the pond to the maximum extent.
iii. It should be hardy and resistant to diseases.
iv. It should be able to survive even in low dissolved oxygen concentration.
v. It must be a prolific breeder and easy to breed in ponds.
vi. It should be predaceous and preferably herbivorous in habit.
vii. It should be tasteful and of high nutrient and market value.
Happa
· It is a rectangular structure made up of a mosquito net and sprayed in the pond on four bamboo poles for breeding and hatching of fish.
· It is a rectangular structure made up of a mosquito net and sprayed in the pond on four bamboo poles for breeding and hatching of fish.
Pond Management
· The following physicochemical constituents of the pond water should be considered during pond management for better production of the fish.
(i) Soil
· The soil should not be porous. The clay loam with deep stratification is used for the control of soil leakage.
(ii) Water
· Water source for the pond should be permanent i.e. from spring, river or irrigation.
(iii) PH
· Optimum pH is 7–8 but pH 5–10 is tolerable.
· Fishes prefer neutral or alkaline water.
· If the water becomes acidic, the lime should be added to increase pH.
(iv) Oxygen
· The concentration of oxygen in water increases due to phytoplanktons or other plants.
· Constant flow of water is the best measure for the oxygen balance in a pond.
· Surface swimming fishes take atmospheric oxygen.
· Some amount of CO2 should be retained in the water for the photosynthetic activity and retention of calcium in the water.
(v) Light
· Fish pond must be at a sunny place for the photosynthetic activity of phytoplankton.
· Light affects the activity of the fries, temperature of the water and growth of other plants.
(vi) Temperature
· Optimum temperature of pond water for the common carps is 20°–30°C.
· Decrease and increase in temperature below and above the optimum level have address effects.
(vii) Turbidity
· It is caused due to dust particles, clay or silt or others.
· Turbidity plays an important role in the productivity of fishes by controlling over other physical factors (light, temperature) etc. So, pond water must not be turbid at all.
(viii) Fencing
· Pond must be well protected against snakes, local carnivorous fishes (Channa, Wallago etc) and other predators.
(ix) Manuring
· Less productive soil needs manuring with cow dung, compost and chemical fertilizers.
· Excessive manuring changes pH of the water and other chemicals to reduce phytoplanktons or other aquatic weeds. Excess nitrogenous fertilizers increase NH4+ ions which may act as nerve poisons to fishes.
Also, Read our other Notes on the Application of Biology: