Detailed Guide to Carp Farming Techniques: Scientific Feeding and Daily Management Methods

The carp is an economic fish species of the order Cypriniformes, family Cyprinidae, genus Cyprinus, distributed throughout the country and one of the most important farmed fish species in China. Common varieties include local varieties such as scaled carp, mirror carp, red carp andHepo carp, as well as improved varieties such as Feng carp, Ying carp, Jian carp and all-female carp.

Biological Characteristics

1. Morphological Characteristics

The fish body is spindle-shaped and slightly flattened, with a grayish-black back, a pale white or light gray belly, and a golden-yellow color below the lateral line and near the caudal peduncle (body color also varies by variety, including golden yellow, orange-red, pink, etc.). The mouth is terminal and horseshoe-shaped, with 2 pairs of barbels, and the maxillary barbels are about 2 times as long as the rostral barbels. The scales are relatively large. The individual is relatively large, commonly 0.5-2.5 kg, with a maximum of over 15 kg.

2. Feeding Habits and Growth

The carp is an omnivorous bottom-dwelling fish. Fry with a body length under 3 cm mainly feed on rotifers and small cladocerans; those over 3 cm mainly feed on cladocerans, copepods, chironomid larvae and other insect larvae; those with a body length over 20 cm mainly feed on chironomid larvae and ciliates; and those over one year old feed on benthic organisms such as insects, snails and clams, as well as fragments of aquatic vascular plants, while algae are also often found in the intestine. Because of its omnivorous diet, wide food range, low requirements for living conditions and fast growth, it generally reaches market size at two years of age; if compound feed is used, it can reach market size at one year of age.

3. Living Habits

The carp prefers to inhabit the lower layer of water bodies. The optimum growth water temperature is 25-32°C; growth slows noticeably above 32°C or below 15°C, and feeding stops below 10°C. The suitable dissolved oxygen level is above 4.5 mg/l; below 2 mg/l it eats less, and at 1 mg/l it stops feeding and comes to the surface for air.

4. Reproductive Characteristics

It generally reaches sexual maturity at two years of age, and some individuals can also mature at one year of age. The spawning season varies by region, and spawning can occur from March to August (with April to June as the peak period); it is a batch-spawning type. Spawning grounds are mostly in shallow lake bays or river bays with dense aquatic vegetation. The eggs are strongly adhesive and firmly attach to aquatic plants immediately after spawning. The number of eggs carried varies with age and individual size, ranging from 150,000 to 800,000. After the eggs are laid, fry can hatch in 4-6 days at a water temperature of 15-20°C.

Breeding Techniques

1. Brood Carp Rearing

(1) Selection Criteria

Good body shape, strong activity and no injuries, with a body length to body height ratio of 3:1, and typical varietal characteristics. It is best for females to be at least 2 winters old and weigh 1.5 kg, and for males to be 2 winters old and weigh over 1 kg. Carp that are reaching sexual maturity for the first time or are in the aging stage have poorer egg-carrying capacity and egg quality, so they are not suitable as brood fish.

(2) Sex Identification

① Non-breeding season: The female has a wide body, high back, small head, relatively large and soft abdomen, small and round-wide pectoral and pelvic fins, and a flat or slightly protruding vent with radiating folds; the male has a narrow and elongated body, a relatively large head, a small and hard abdomen, large and pointed-long pectoral and pelvic fins, a slightly inward-concave anus, and no parallel folds.

② Breeding season: The female has a soft, round sac-shaped abdomen, and the anus and genital pore are relatively large, slightly red and protruding; the male has a relatively small abdomen, obvious secondary sexual characteristics "nuptial tubercles" on the operculum and pectoral and pelvic fins, an inward-concave anus and genital pore that are not red or swollen, and milky-white semen flows out when the abdomen is lightly pressed.

(3) Rearing Management

① Rearing: The brood fish rearing pond is 1-2 mu, with a water depth of about 1.2 m, sheltered from wind and facing the sun, with convenient water inlet and drainage. Stock 150-200 kg per mu. During artificial breeding, separate males and females to prevent them from mating and spawning on their own. Disinfect with quicklime or bleaching powder before stocking.

② Management: Intensify brood carp rearing, and feed high-protein feeds such as soybean cake, silkworm pupae and fish meal. In recent years, some manufacturers have developed brood fish feed. This feed is rich in ve and other vitamins, can promote development and improve stress resistance, and has good results. At the same time, pay attention to regulating water quality during rearing, often add fresh water, and maintain slight water flow to stimulate gonadal development.

2. Induced Spawning and Hatching

(1) Timing of Induced Spawning

Induced spawning can be carried out when the water temperature rises and stabilizes above 16°C. Usually, during the period from Qingming to Guyu, after a cold wave has passed and the temperature has risen and stabilized, induced spawning can be carried out.

(2) Induced Spawning Methods

① The natural spawning type is a very common method because its investment and scale are both relatively small.

◆ Spawning pond: A pond with an area of 0.5-1 mu, a water depth of 1.2 m and convenient water inlet and drainage is sufficient. Fish can be stocked one week after disinfection with quicklime.

◆ Artificial spawning nest: Used to attach fish eggs. Choose materials that are soft in texture, good in toughness, non-toxic and not easily rotted, such as pine branches, palm sheets, polyethylene sheets (woven bags), poplar roots, etc. Before use, they must be washed, tied into bundles and disinfected (0.3‰ formalin or malachite green). Rice straw is not suitable as a spawning nest because it rots easily.

◆ Hatching pond: It can also serve as a fry rearing pond. The area should be small (1-2 mu), with little silt, a water depth of 1 m, and disinfected. Both the inlet and outlet must be filtered with densely meshed netting to prevent impurities from entering the pond and fry from escaping.

◆ Combined-pond spawning: According to a female-to-male ratio of 1:1-1.5, place 35-30 groups of well-matured brood carp into the pond and slowly add fresh water. At the same time, stretch 1-8 thin iron wires across the water surface, and hang artificial spawning nests on the wires (or split bamboo in two and clamp them in the middle on the water surface). Usually, 4-6 spawning nests should be provided for each group of brood fish.

◆ Management: Spawning generally occurs from 22:00 to 9:00 and lasts 2-3 days, so the spawning nests should be checked and cleaned every afternoon, the nests with attached eggs should be moved into the hatching pond, and new spawning nests should be added. If spawning is poor after combining the ponds, the water level can be lowered to let sunlight shine on the pond, more ve can be added to the feed, or slight water flow can be used as stimulation. To ensure the uniformity of fry, eggs from the same day should be put into hatching together, which can also prevent an increase in the number of dead eggs caused by eggs sticking together into clumps.

② Artificial induced spawning is mostly seen in fish breeding farms.

◆ Injection of induced spawning agents: For each kg of female fish, use 600-1000 iu of human chorionic gonadotropin (hcg) or 30-50 micrograms of luteinizing hormone-releasing hormone analogue (lrh-a), or use a reduced-dose mixture of the two; the dose for male fish is halved. Generally, at 6 p.m. on a sunny day, inject the predetermined dose once into the thoracic cavity at the base of the pectoral fin, then immediately move the fish into the spawning pond, and add fresh water for half an hour. At a water temperature of 18°C, spawning behavior occurs after 6-15 hours (the higher the water temperature, the shorter the response time, and vice versa).

◆ Spawning and fertilization: After induced spawning, brood fish can spawn on their own in the pond, using the same method as the natural spawning type. If artificial egg collection is used, the fish can be caught before the peak of spawning behavior, the water on the fish body wiped off with a towel, the eggs squeezed into a dry porcelain basin, and semen quickly squeezed in, stirred with a feather to allow full fertilization, then the fertilized eggs evenly spread on the spawning nest and placed in the hatching pond for hatching. Alternatively, use a talc solution to remove adhesiveness and then carry out flowing-water hatching. At a water temperature of 16-22°C, fry emerge in 3-5 days.

(3) Hatching Management

① Natural hatching: Put 300,000-500,000 fertilized eggs per mu of pond, and eggs from the same day should be put in together to ensure uniform fry size. Special attention should be paid to preventing saprolegniasis, and the spawning nests with attached eggs can be pre-soaked in 0.3‰ formalin or malachite green.

② De-adhesion hatching: The key is to adjust the water flow speed so that the fish eggs do not sink but remain suspended in the water. At the same time, prevent the sand screen from clogging. When fry begin to hatch, slightly reduce the flow speed to prevent excessive water flow from consuming the fry's energy.

③ Precautions: Improving the hatching rate is the key to artificial breeding. The main reasons affecting the hatching rate are sudden weather changes during the spawning period, poor water quality, low dissolved oxygen, and mold parasitism on fish eggs, etc., and measures should be taken to prevent their harm.