At present, Hyriopsis cumingii is the most important shellfish for cultivating pale pearls in China.
1. For most mussel farmers, pearl mussels are generally not cultivated. Judging from the development of industrialization, there is no need for professional companies to complete the three production links of "artificial seedling raising-operation mussel culture-pearl culture operation". Generally, farmers only engage in pearl mussel breeding. Judging from the current production situation, most people buy young mussels, raise and manage them themselves, and then hire people to manage them. So briefly introduce the breeding process of mussels.
When the breeding season of mussels comes, female mussels pregnant with eggs are generally selected directly from mature pearl mussels, and when their fertilized eggs develop into hookworm larvae, they are collected (delivered) with Pelteobagrus fulvidraco in time.
20-30 small fish parasitized with hookworm larvae can be placed in each square meter of running water seedling pond. The nursery pond should master a certain amount of water flow, but the flow should not be too fast. Feed the fry every day to make them grow normally. When the water temperature is above 30℃, hookworm larvae mature in 4-7 days, and it takes 7-9 days at 25-30℃. The hookworm larvae parasitic on fish begin to live freely after shedding, which is called juvenile mussel. This process is called seedling removal. Young shellfish (65438±0-2mm) were cultured in shallow ponds in nursery until they grew to about 65438±0cm. The production process is as follows: pregnant mother mussels → hooked larvae → Pelteobagrus fulvidraco seedlings → young shellfish cultivation → young shellfish.
2. There are many ways to cultivate young mussels to operate mussels, but mussel farmers in Zhejiang widely use the method of cultivating mussels in small cages with large water surface in production, and the effect is quite obvious. The young mussel of 1 cm was directly cultivated into an operation mussel of about 8 cm, and the time was shortened to about 3 months. This reform made it possible to raise seedlings and pearls by surgery that year.
The general specification of this Xiao Mu cage is (40-45) cm× (40-60) cm× 10 cm, and it is made of Chinese fir (or bamboo) strips, and the specification of Chinese fir strips is generally (1.5-2) cm× (3-4) cm. After the wooden frame is nailed, it is closed with a 2 cm net, leaving a seam on the upper part. The bottom of the cage is padded with plastic film and placed with fertilizer mud. It is appropriate to put about 0/50-200 young shellfish in each net, so it is expected that more than 60% young shellfish will be cultivated into operational mussels in the autumn of that year.
The aquaculture water area should be above 10 mu, and the water level should be at 1.5-2.5 meters. 3-5 days before the young shellfish are put into the box, base fertilizer should be applied according to the water environment (xintang or laotang) and the fish stocking situation (50-200 flowers and silver carp in a certain proportion/mu) to improve the water quality. Make the water light brown or yellow-green, and the transparency is 30-40cm. The water quality of young mussels should not be too fat before 3 cm, otherwise a slightly higher concentration of ammonia and nitrite ions will inhibit their growth.
In the process of culture, topdressing should be done in time according to the change of transparency and water color, generally once every 10- 15 days, and wet pig manure 150-250 kg/mu should be used each time. Fertilizer must be fully fermented and decomposed. It is best not to use chicken and duck droppings. It is recommended to use professional compound fertilizer (the dosage can be according to the instructions), which is safe and efficient.
When the young mussels grow to 3-5 cm, the amount of fertilizer can be appropriately increased to improve water fertility (transparency 30 cm). In addition, quicklime should be applied every 10- 15 days (10 kg/mu). During the whole cultivation period, topdressing should be done in time when the water becomes weak and the transparency increases. But blue-green algae must not flourish, otherwise the transparency will drop below 25 cm.
If scientific management can be carried out according to the requirements, 60% of the young shellfish can reach the surgical specifications in less than 3 months.
(2) Operation technology of freshwater seedless pearls
Transplanting epithelial tissue of shellfish mantle into cultured pearls has always been a basic surgical technique for artificial pearl cultivation. After years of efforts, we have scientifically combined tear film technology with systematic disinfection technology to form a set of new surgical operation techniques, processes and quality management measures. The training of operators and the practice of aquaculture production show that the technology and its management measures not only greatly improve the high-quality pearl rate of "big, bright, round and bright", but also the survival rate of pearl mussels after operation is over 95%, and can effectively prevent the occurrence of mussel diseases.