High economic returns from raising adult crabs as a supplementary crop in fingerling ponds

Raising adult crabs as a supplementary crop in fingerling ponds, relying on high density for success, practicing ecological farming, and replacing concentrated feed with coarse feed, is a new low-input, high-output farming model that the author has summarized from years of practice. Last year, in a pond of two mu, the author invested a total of 1,000 yuan in fingerling costs and feed costs. The result was an output of 70,000 "huopian" fingerlings worth 3,000 yuan, 20,000 one-year-old fingerlings worth 4,000 yuan, and 40 kg of adult crabs worth 1,000 yuan, for a total output value of 8,000 yuan. After deducting costs, a net profit of 3,500 yuan per mu was obtained, achieving the goal of low input and high output.

Supplementary stocking method: At the end of April, 75 kg of lime per mu was used to thoroughly clear the pond. On May 18, 250,000 grass carp and silver carp/bighead carp fry were stocked, half grass carp and half silver carp/bighead carp; on May 20, 2,000 juvenile bean crabs were stocked.

Feeding method: One month after the fry were stocked into the pond, soybean milk was fed once a day. After one month, when the fry had grown to 3-4 cm, concentrated feed was stopped, and from then on only duckweed (fu lang cao, also called sesame duckweed) was fed. This aquatic plant is small, with roots only as thin as a hair, and grass carp love to eat it very much. At first the grass carp forage on the roots, and after about a week they begin to forage on the duckweed bodies. The feces excreted by the grass carp also fertilize the water and can be eaten by silver carp and bighead carp. Especially in the three high-temperature months of July, August, and September, herbivorous fish are particularly fond of eating it, and river crabs are no exception. From mid-June to late September, a total of 7,500 kg of duckweed was fed, and the pond was almost never without grass, so the grass carp grew especially fast. After October, when aquatic plant resources were scarce, fresh chicken manure was fed exclusively. Chicken manure contains large amounts of feed that the chickens did not digest and absorb, as well as soybean cake, corn, and other concentrated feed that the chickens pecked and dropped into the manure, and these feeds are palatable feed for grass carp and river crabs. There is one principle for the feeding method: feed as much as the fish and crabs will eat. In this way, the feed will not ferment in the water and consume oxygen. If too much bait is fed at one time and the fish and crabs cannot forage it all, it will ferment in the pond, consume oxygen, and affect the growth of the fish and crabs, and in severe cases cause a pond-wide fish kill. During the entire rearing process, 3,000 kg of fresh chicken manure was fed, and the pond water quality was relatively fertile, generally controlled at about 5-10 cm, meeting the requirement of fertile water and strong fish. In the past, books required pond water transparency to be 30-40 cm, but this standard cannot meet the requirements of high yield. During the rearing process, repeated catching and restocking were maintained. When the fish grew to 3-5 cm, that is, "huopian" size, they were continuously caught and restocked, and a total of 5 catches were made, harvesting 70,000 "huopian" fingerlings worth 3,000 yuan. Pond water fed with chicken manure generally becomes acidic, which affects the growth of fish and crabs, so quicklime must be used regularly to adjust water quality, generally 15 kg per mu per meter of water depth. The quicklime used must be lump lime, mixed with water and splashed over the whole pond. This can neutralize acidity and keep the pond water neutral, which is very beneficial to the growth of fish and crabs, preventing disease and purifying water quality while promoting healthy growth of fish and crabs.

Benefits of supplementary stocking: 1) After river crabs are raised as a supplementary crop in fingerling ponds, the pond has relatively abundant feed for the river crabs to forage. Supplementary stocking often gives better returns than separate stocking. 2) No anti-theft facilities are needed. 3) Practice has proved that raising river crabs as a supplementary crop in fingerling ponds generally does not cause disease, so less or no medicine is needed. 4) The river crabs should be fully harvested within 15 days before and after National Day, so no effort is needed to guard them. 5) Adult fish ponds can also imitate this method with very good results, generally increasing income by 200-300 yuan per mu.