Technical Points and Precautions for Catfish Farming in Rice Paddies

In recent years, fish farming in rice paddies in Wuyishan City, Fujian Province, China, has seen further development in terms of farming methods, scale and species. Stocking local catfish or Clarias leather in mountain rice paddies has good economic benefits. The techniques for farming catfish are summarized and introduced as follows:

Selection and Facilities of Rice Paddies for Catfish Farming Paddy Conditions: Any early, middle or late rice paddy with sufficient water supply, convenient irrigation and drainage, strong water retention, that does not dry up in drought and is not flooded by floods can be used for catfish farming. However, late rice paddies are best for catfish farming.

Basic Paddy Facilities: ① Raise and reinforce the field ridges. The ridges should be raised to 40 cm~50 cm in height and 30 cm~35 cm in width, and must be solid and firm, not collapsing or leaking, to prevent fish from escaping. ② Dig fish pits and fish trenches. A fish pit, also called a fish hole or fish nest, is a deeper area in the paddy field. The fish pit is the main place for fish to rest, escape the heat and grow, and is also an important measure for resolving the conflicts between rice paddy fertilization, pesticide application and field drying. Its shapes include square, rectangular and circular. It can be dug in the middle, at the field edge or at the water outlet, choosing as concealed a spot as possible to prevent disturbance, prevent theft, and facilitate cleaning, observation, feeding and harvesting of fish. Each fish pit is 3 sq m~5 sq m, 50 cm~80 cm deep; slightly deeper is even better, which is beneficial to fish growth. The fish pit area accounts for 3%~5% of the area of that field.

The fish trench is the passage for fish to live and enter the fish pit. It is generally 30 cm~35 cm wide and 30 cm~40 cm deep, with layout shapes such as the “sun” shape and the “field” shape, etc., often determined by the shape of the field. The fish trench area accounts for about 3%~5% of the paddy field area. The time for digging fish trenches and fish pits can be before transplanting rice seedlings or after. Digging before transplanting is convenient to do and easy for soil removal, and the trench quality is good, but it must be re-tidied during plowing and transplanting; digging trenches after transplanting makes soil removal more troublesome. Seedlings that are pulled up should be replanted on both sides of the trench as much as possible, trying to reduce rows without reducing plants.

Installing escape-prevention screens: Fish-blocking screens should be installed at the water inlet and outlet of the paddy field. The water inlet and outlet should be set at the field ridges on opposite corners, with smooth water flow passing evenly through the entire field. The fish-blocking screen material can be made of bamboo rafts, plastic strips or wire mesh. Generally 60 cm long, 40 cm wide, with a height exceeding the field ridge by 20 cm~40 cm, embedded 10 cm~15 cm into the soil at the lower part of the field ridge, to prevent catfish from jumping over against the water flow or escaping by drilling from the bottom.

Farming Management Techniques

Stocking Species: In order to make full use of the natural aquatic feed in the rice paddy, a farming model is adopted with local catfish or Clarias leather as the main species, supplemented with a small number of grass carp and common carp.

Stocking Size and Quantity: In the catfish-based model, catfish fingerlings of 1.5 cm~3 cm in size are stocked at 300~500 fish. The farming period is generally April~August. Local catfish individuals are large and can grow to an average of 0.25 kg~0.5 kg; Clarias leather can grow to 1 kg~1.5 kg. The survival rate is 40%~50%, and the yield can reach 60 kg~120 kg, with a certain amount of grass carp and common carp harvested as well, showing remarkable results. Rice grain yield can reach about 500 kg~600 kg.

Stocking Time: Generally 7 days~10 days after transplanting rice seedlings, the fingerlings can be released into the fish pits. If the water temperature is suitable, about 16°C~20°C, and the paddy field is relatively rich in feed, some commercial feed can be appropriately put in; if the paddy field is relatively lean, more feed or an appropriate amount of organic fertilizer, etc. can be added so that the fingerlings have food, allowing them to adapt to the new living environment for future feeding and management.

Management Techniques: In rice paddy catfish farming, rice is the main focus. We should make full use of the paddy field ecological conditions, correctly handle the relationship between paddy field fish farming and fertilization, pest control and field drying, so that rice and fish benefit each other and coexist, achieving the goal of a double harvest.

(1) Fertilization: Excessive fertilization or incorrect methods are harmful to fish. Fertilization should be mainly base fertilizer, supplemented by top dressing. Organic fertilizer must be fermented before application. The amount used is about 500 kg per mu. For chemical fertilizer application, urea 5 kg~10 kg per mu, ammonium sulfate 10 kg~15 kg, potassium nitrate 3 kg~7 kg, potassium superphosphate 5~10 kg. When fertilizing, try to avoid harming the catfish; half-field alternate application can also be used.

(2) Pesticide Application: Fish farming in rice paddies can devour some pests. For rice diseases and insect pests, high-efficiency and low-toxicity pesticides should be selected according to the specific problem, and the concentration should be strictly controlled. Before applying pesticide, the fish trenches should be cleared and dredged, and the water level should be lowered so that the fish enter the fish pits; only after inspection can the pesticide be applied. Minimize the harm of pesticides to fish. After applying pesticide, observe the fish's movements and add fresh water in a timely manner, so that the fish can continue to be safely raised until harvest.

(3) Field Management: The key to a bumper rice harvest and a good fish harvest is that the fish do not escape and do not die, among which not drying up the water is the most important. Therefore, frequent field patrols and inspections should be carried out. Check the fish's activity, feeding and water quality conditions as well as the growth of the rice, to decide on feeding, fertilization and pesticide application; check whether the field ridges have collapsed or leaked, whether the fish-blocking screens are firm, and whether harmful animals have sneaked in. If there is no rain for a long time, guard against drought; before heavy rain, guard against waterlogging and escape. For feeding of grown fish, be sure to observe water quality and fish conditions, and follow the feeding principles of regular timing, appropriate amount, fixed location and guaranteed quality.

Harvesting After 5~6 months of field rearing, the fish have reached the harvest season. Fish are generally harvested 10 days~15 days before rice harvest. Before harvesting, first dredge the fish trenches and prepare fishing tools, such as dip nets, small pull nets, net cages, wooden buckets, etc. When harvesting fish, release the water slowly, so that the fish gather from the fish trenches into the fish pits and are captured. Those reaching market size are sold, and small-sized ones are kept and transferred to small ponds to continue being raised the next year. After the fish are harvested, the rice paddy can be drained and the rice harvested.