Breeding technique of Boleophthalmus mandshurica in soil pond

Turtle fish is a kind of fish with warm water, wide temperature and wide salinity. Its meat tastes delicious, has the effect of nourishing and strengthening the body, and is deeply loved by the coastal people in Zhejiang, Fujian, Guangdong, Taiwan and other provinces and the Japanese, so the market demand is very large and the price is expensive. Due to the gradual decline of the resources of the big fish, the culture of the big fish was started in the southeast coast of China in the 1980s. Because of the characteristics of short food chain, less disease, long-distance transportation of live fish, easy to master culture technology, low culture cost and high economic benefit, the culture of big fish has developed rapidly. At present, the culture area of big fish in Fujian Province has reached more than 50,000 mu. However, so far, it still depends on natural seedlings. In order to protect the natural seedling resources and promote the sustainable development of the aquaculture industry, it is urgent to carry out the study on the breeding of the fish in the soil pond. In 2003, Xiamen University and Xiapu County Aquatic Technology Promotion Station in Fujian Province undertook the major science and technology project in Fujian Province, "Research on productive breeding Technology and standardized breeding of Blatfish". The project was appraised in January 2006, among which: a total of 1.254 million full-length 1.6~3.1cm fry were cultivated in outdoor soil ponds in 2004 and 2005, and the breeding technology of earthen ponds occupies the leading level in the world. In this paper, the main points of breeding techniques in big blister fish soil ponds are introduced as follows:

I. Seedling facilities

The main results are as follows: 1. The bottom material of the seedling pond is silty clay, the area of each pond is about 1 mu, the depth of the pond is 0.8 ~ 1.3m, the dike is firm and watertight, and it is equipped with intake and drainage system. The four sides of the pool are surrounded by 80 mesh silk screen. A bracket is arranged in the pool to cover the sunshade net above the pool. About 1 inflatable stone per lom2.

2. The reservoir, sand filter and bait biological culture pond are built in the high tide area, the nursery pond covers a total area of 5 mu, and a storage tank is built with an area of 500m2 and a depth of 2m. The most exciting part is to incorporate sea water from the sluice gate, and to store water by pumping water at low tide. A sand filter with an area of 40m2 was built. The sea water was filtered and entered into the seedling pond and the bait biological culture pond through the 120mesh silk mesh. In order to facilitate promotion, the direct extraction of seawater can also be filtered through a double-layer 120-mesh silk cage. A small pot-shaped cement pond (1~2m2) was built to hatch shellfish trochophore larvae, and one or two soil ponds were left to release EM (effective microflora preparation), compound fertilizer and fish pulp to cultivate food organisms such as rotifers and copepods.

2. Clear the pond and cultivate benthic diatom parent fish 45 days before stocking, clean the pond with water and apply quicklime 100kg or bleaching powder 10kg per mu to kill enemy organisms. After washing the pond for 5-7 days, the rice bran was fed with 20kg per mu, 5~1Ocm was fed, compound fertilizer 5~10ppm was applied, and benthic diatoms were cultured.

3. Parent fish are released 30 days before spawning (usually in early March of the lunar calendar). 2-year-old individuals from pond culture and / or intertidal tidal flat were selected as parent fish. When the sex ratio of female to male is 1:1, male and female parent fish can be identified by the appearance of cloacal mastoid. The cloacal mastoid of female fish is large and obtuse, showing red and swollen shape, and the male cloacal mastoid is narrow and pointed. The stocking density is 50kg per mu and the parent fish is about 25g per mu. The parent fish are disinfected by fresh water and povidone iodine before release. During the period of parent fish cultivation, the water level should be maintained at 5~10cm, and the management of benthic diatom culture should be strengthened to ensure the nutritional requirements of parent fish.

4. During the period of natural spawning and hatching reproduction, the parent fish in the pond spawn two batches a month, and the spawning date is from neap tide to neap tide, that is, from the eighth to thirteenth and twenty-third to twenty-eighth lunar calendar, the spawning period of each batch is about 6 days. Before spawning, the water level in the pond was raised to more than 0.7m, and the female and male parent fish entered the cave freely and spawned in the spawning chamber of the cave. The fertilized eggs adhered to the top and periphery of the spawning room and hatched the larvae after 5-6 days. The larvae came out of the hole at the age of 1 ~ 2 days after hatching.

5. Cultivation of larvae, juveniles and juveniles. Larvae and juveniles are reared in the original pond. Chlorella and Brachionus plicatilis were introduced into the nursery pond ahead of time. 10ppmEM, 2~3ppm compound fertilizer, 1~2ppm Huolidan (compound diatom nutrition produced by Xiamen Johnson Science and Technology Co., Ltd.) and copepods in 2~4pm fish pulp culture pond were applied. When the bait in the pond water is insufficient, the bait such as rotifer and copepod must be extracted from the bait biological culture pond in time, and the artificially hatched shellfish trochophore larvae can also be released and sea mud (ooze rich in diatoms and organic debris) can be evenly sprinkled into the pond with a high-pressure spray gun, and egg yolks and Prawn Crackers can also be replenished. The larvae were fed 2-3 days after hatching. The series of diets for larvae, juveniles and early juvenile fish are granular organic detritus, bollworm, polychaete and shellfish trochophore larvae, copepod nauplii, copepod larvae and adults, and benthic diatoms. The species and individual size of food organisms in the breeding pond are diversified, which can basically meet the needs of larvae, juveniles and juveniles at different developmental stages and different individuals. During the seedling raising period, the water level increased gradually, and when the water level in the seedling pond reached the upper limit, the water began to be changed appropriately, and the salinity of the pond water was adjusted to 15: 20 by introducing fresh water. When the water temperature is not more than 32 ℃ during the seedling raising period, the water temperature can be controlled by laying a sunshade net over the soil pond and increasing the water level. The same kind of cannibalism will not occur during the cultivation of different batches of larvae, juveniles and juveniles in the same pond. Often check the water color of the pool and monitor the changes of dissolved oxygen content in the pool water. When the water color is yellowish green, the water quality is better. If it is found that the eutrophication of pond water leads to oversaturation of dissolved oxygen or too low dissolved oxygen and uneven light, the aerator should be turned on in time. Oversaturation of dissolved oxygen will lead to the expansion and death of the swim bladder of larvae. During the period of fish fry cultivation, the high water level affects the reproduction of benthic diatoms. A foam board of about 4m2 can be set up in each pond to feed on artificial compound feed and surface mud (ooze rich in diatoms and organic detritus) for parent fish to eat.

VI. Fry fishing

The early juvenile fish (34 days after hatching) rely on their ventral fins to attach to the net around the pond. At this time, fish fry can be caught in batches with manual nets and temporarily reared in soil ponds rich in benthic diatoms. When harvesting the last batch of fish fry, the pond water can be drained and caught by treading net, setting net and trawling net.