About Fisheries: Fish farming is a type of aquaculture where fish are bred in enclosures with the purpose of being sold as food. It is the sector of animal food production that is expanding at the highest rate. Approximately half of the world’s fish is now raised in these artificial habitats. Salmon, tuna, cod, trout, and halibut are some of the most often farmed species. Mesh cages submerged in natural bodies of water or concrete enclosures on land are examples of “aqua farms”.
Pre-stocking management
During this time, interested farmers can build new fishponds. Rectangular clayey loam ponds with a depth of 1.5-2.5m and a slope ratio of 2:1 are generally regarded suitable. Maintain a water depth of up to 6-7 feet (2 metres) in the winter to allow space for fish in the warmer bottom layer of the pond.
Reduced oxygen levels are induced by fluctuations in photosynthetic activity during the rabi season, which are driven by a drop in day length and light intensity. To keep the dissolved oxygen level in ponds between 6.5-8 mg/l, aeration with aerators or water exchange with a submersible pump is recommended.
Remove undesired weeds and aquatic insects using a combination of hand and mechanical methods at regular intervals. Doses of organic and inorganic fertiliser should be given according to soil and water quality factors. If the water becomes murky or dark in colour and the transparency decreases, fertilisation should be avoided.
Stocking management
Always buy high-quality fish seeds from a reputable hatchery. Loosen the mouth of the plastic bag and gently dip the bag for free flowing after 15-20 minutes to condition the fish. Fish overstocking should be avoided. The ideal stocking density is from 7500 to 8000 fingerlings per hectare.
Encourage the use of composite fish culture, which includes a variety of fish species, at appropriate stocking rates. Generally, six (6) species carp culture is the most adopted one in Bihar- which includes Catla: Rohu: Mrigal: Silver carp: Common carp: Grass carp at the ratio 1.5:2:1.5:1.5:1.5:2.
Pothia, mola, murrels (murrai), and other small indigenous fishes can be introduced to the fishpond. In comparison to other large-sized cultural fishes, one kilogramme of small indigenous fishes contains 1000 times more vitamin content. Diversify potential species for freshwater fish production, such as Amur carp, Jayanti Rohu, Pacu, Mono sex Tilapia, Puntius gonionotus, Bighead carp, Magur, Pabda, and giant river prawn, among others.
To develop adult prawns from post larvae in seasonal ponds, build a polyhouse out of low-cost, locally available materials. When the ambient temperature lowers, the polyhouse helps to regulate the temperature, which is good for high-cost fish like Macrobrachium rosenbergii (Giant river prawn).
Post-stocking management
Maintain a pH of 6.5-7.5 in the water. Apply lime if the level falls below the ideal level, and gypsum if it rises over the optimum level. When the temperature dips below 10°C, don’t feed.
Because of the decreased metabolic rate, fish growth slows from mid-November to February and then picks up when the temperature rises. Observe the fish by netting the pond once every 15 days and giving them a bath with potassium permanganate solution.
If you see any strange fish behaviour, take urgent action to eliminate it. For example, when fish begin to move in unusual patterns and come close to the top of the water to gasp, this indicates a low oxygen concentration in the fishpond, necessitating quick aeration.
Fish are more susceptible to bacterial, fungal, parasitic, and viral diseases such as tail or fin rot, dropsy, gill fluke, EUS, and fungal infections. As a result, an emergency treatment for the fish is required, and it is recommended that the pond be treated with CIFAX @ 1l/ha immediately before the winter season begins. Apply potassium permanganate at a rate of 3-5 kg/ha, or limestone at a rate of 150-200 kg/ha. Salt solution can also be treated in ponds at a rate of 250 kg/ha, which helps to prevent fish from illness outbreaks over the winter.
Fish based Integrated Farming System
Horticulture – Duck-based fish aquaculture is regarded the greatest approach for year-round income creation in Bihar among all available possibilities.
Ducks should be stocked at a density of 200-300 per hectare, which is sufficient to create manure and act as a bio-aerator for the fishpond.
Biofloc farming
For farmers who don’t have enough acreage to build a pond, this is a novel technology.Fish aquaculture with a low or no water exchange system that uses wastewater.
Pangas, Magur, Kawai, Tilapia, and Common carp are suitable species for this farming technique. A budget of Rs. 7-8 lakh is required to build a biofloc set-up consisting of 7 tanks with a diameter of 4 metres and a height of 1.5 metres.
The availability of electricity 24 hours a day, seven days a week is a major constraint in this technology. In big reservoirs, cage culture is used.An essential water resource (Bihar’s chaurs and mauns) for maximising fish production. Cage culture may be promoted in areas with a year-round water depth of 10 metres and a water spread area of 1000 hectares or more.
Harvesting
Crafts used for catching fish must be rinsed in soap solution, then dipped in 1 percent sodium hypochlorite solution for 5 minutes before drying. After each use, disinfectants or a home-made neem solution should be applied to fish-catching equipment.
Fishing in freshwater bodies will be limited to a maximum of two people during vessel operation. Indigenous vessels operating in each region must adhere to the 3m safe distance guideline when fishing.