What factors affect the profitability of crayfish farming?

Genetics and broodstock quality

Because crayfish have a natural breeding habit, the vast majority of farmers adopt a model of stocking once a year and harvesting for many years, which inevitably leads to inbreeding among the crayfish, ultimately causing genetic degradation of the crayfish, with individuals becoming smaller and smaller. In addition, during the farming process they all adopt the method of harvesting the large ones and keeping the small ones, so when it comes time to select and retain broodstock around September each year, the large-size crayfish have long been sold off, so only the smaller crayfish are left as broodstock for the next year. Such broodstock itself is poor, and the quality of the next generation it breeds is even harder to guarantee.

It is recommended that farmers thoroughly clear the pond once every 3 years, removing all crayfish in the pond without leaving a single one, and replace them with new broodstock the following year, or introduce a certain number of large-size crayfish from farmers elsewhere around September each year as broodstock. Note: when introducing broodstock, it is enough to introduce crayfish of only one sex from the same place. If both male and female broodstock are introduced from the same place at the same time, inbreeding problems may likewise occur. Broodstock selection requires complete appendages, a robust constitution, no disease or injury, strong mobility, and a body weight of about 30-50 g each.

Water quality causes

In recent years, due to the influence of climate factors, our province has had drought and little rain every spring, so most farmers' ponds have relatively shallow water levels in spring. However, as temperatures rise and the amount of feeding increases, the decomposition of leftover feed, feces and organic matter in the pond all has an adverse effect on water quality. At this time there is no fresh external water to promptly refill and exchange to regulate water quality, and water quality directly affects crayfish feeding, molting and growth, all of which constrain the final size of the crayfish.

It is recommended to alternately use photosynthetic bacteria and quicklime to splash the whole pond about every half month to improve water quality, regulate the pH of the water body, and reduce the ammonia nitrogen content in the pond. In addition, regularly apply monocalcium phosphate to increase the content of ionic calcium in the pond water to promote crayfish molting and growth. The dosage of monocalcium phosphate is generally 2 kg per mu per meter. When external water is available for exchange, exchange fresh water about every 7-10 days, with each exchange amounting to about 15%-20% of the original pond water volume.

Feed causes

When feed is lacking, of poor quality, or nutritionally incomplete and cannot meet the normal growth needs of crayfish, it will certainly affect crayfish molting and growth, resulting in smaller sizes. However, if high-protein concentrated feed is fed for a long time, it will lead to nutrient accumulation in crayfish and cause precocious sexual maturity and stop growth, ultimately also resulting in smaller sizes.

Crayfish are omnivorous animals and can feed on both animal-based bait and plant-based bait, so we must consider both aspects. We should not only feed some high-protein concentrated feed, but also feed some grain-based plant feed and animal feed such as live snails. In addition, aquatic plants such as alternate-flowered waterhyssop and whorled waterweed should be planted in the pond, because on the one hand aquatic plants can supplement plant-based feed for crayfish, and on the other hand aquatic plants can also purify the pond water quality. Moreover, ponds with well-grown aquatic plants also have a higher crayfish survival rate and better quality, but the area of aquatic plants must not exceed 60% of the total pond area. Also, around Qingming each year snails must be stocked in the pond, generally about 500 kg per mu. Afterward, whether to stock additional snails can be determined according to the specific conditions of the pond.

Density causes

Due to the natural breeding habit of crayfish, it is indeed very difficult to always control the appropriate farming density during pond farming, and crayfish are naturally aggressive. When the density is too high, cannibalism becomes extremely severe, and crayfish will delay molting because they cannot find a safe place to molt, resulting in fewer molts during the farming process and ultimately smaller sizes.

During crayfish farming, the method of harvesting the large ones and keeping the small ones should be adopted to reduce the farming density in the pond. Do not count on waiting until the market price of crayfish rises before selling, because even if the market price is high, if the crayfish raised are too small in size, they still cannot sell for a high price. On the contrary, even if the market price is not high, as long as the crayfish are large in size and good in quality, they will still sell for a good price. Crayfish have the habit of clinging to aquatic plants, so planting aquatic plants such as alternate-flowered waterhyssop and whorled waterweed in the pond can not only provide hidden places for crayfish to molt, but also increase the living space for crayfish and reduce opportunities for cannibalism.

Disease causes

Disease is also a main reason restricting the size of crayfish, especially ciliate disease, which is the most common. When ciliates parasitize on the crayfish body, they absorb nutrients from the crayfish body and make the crayfish thin and weak. The crayfish cannot molt and grow normally because of nutritional deficiency. Also, when ciliates parasitize the gills of crayfish, they affect the respiratory function of the crayfish gills, causing the crayfish to be unable to breathe normally and to remain in a long-term state of oxygen deficiency. Ultimately, due to long-term oxygen deficiency, the crayfish cannot feed, molt and grow normally, resulting in smaller sizes. In addition, the parasitism of ciliates may even cause other diseases in crayfish and mass mortality, and such crayfish are not wanted by consumers after entering the market.

1. Around one week before the "barley yellowing" period each spring, around one week before the "plum rain season" arrives (the Jianghuai region generally enters the plum rain season in late June each year), and around one week before "White Dew" in autumn, use medication for prevention respectively, that is, first use an insecticide once, and the next day use a disinfectant once.

2. In the high-temperature summer season, alternately use photosynthetic bacteria and quicklime to splash the whole pond about every half month to regulate water quality, and exchange fresh water about every 7-10 days to keep the water quality fresh, with each exchange amounting to about 15%-20% of the original pond water volume.