Wen Zhu said
Editor丨 Zeu said
preface
Sturgeon, also known as swordfish, is a large freshwater fish, distributed in China's Yangtze River system, Pearl River system, Taiwan freshwater river basin and Southeast Asia, its body is large, the head is large, the mouth lobes are wide, about 3 times the length of the head, the fish body is spindle-shaped, the side is flat and thin, and the abdomen is round; The scales are small and stiff, fan-like; The scales have developed spines with protective effect.
Spoonnose sturgeon is a genus of fish in the order Cyprinidae, Cyprinidae, subfamily Sturgeon, and spoonnose sturgeon. Since the fish has no teeth, it cannot chew the food into small pieces and swallow it directly into the gastrointestinal tract when eating. The fish is known as the "giant panda in the water" because of its unique living habits and physiological characteristics, and is currently listed in the Red Book of Endangered Animals in China.
Distribution and habit characteristics of the spoonnose sturgeon
Spoonnose sturgeon is a large sturgeon living in freshwater, but also one of the earliest freshwater economic fish found in the Yangtze River basin of the mainland, spoonnose sturgeon was originally only found in the upper reaches of the Yangtze River in the mainland Jinsha River and Min River, in the late 80s of the 20th century, in Yunnan Luquan Jinsha River Gorge section, Guizhou Weining Daitang Reservoir, Chongqing Wushan Daning River and other places, there are distribution records of spoonnose sturgeon.
At present, the distribution of spoonnose sturgeon has been recorded in Heilongjiang, Liaoning, Jilin, Hebei, Inner Mongolia, Xinjiang and other places in the mainland.
Spoon sturgeon is a carnivorous fish, preferring to inhabit clear water, slow water flow and high dissolved oxygen content of water bodies, mainly feeding on small invertebrates in the water, its diet is similar to that of Chinese sturgeon, mainly animal food.
During the spawning and breeding period, adults are mostly concentrated in estuarine waters for migration and spawning, usually adults and juveniles go up the river together; During the spawning period, juveniles migrate with broodstock to upper rivers or lakes to spawn.
The spoonnose sturgeon enters the breeding season from the end of September to the beginning of October every year, and the peak spawning period is March ~ April of the following year; During the breeding season, broodstock have obvious circadian rhythms, males are mostly active at night to the deep water layer, and females are mostly active in shallow waters.
Sturgeon has typical ovoviviparous characteristics, and the fertilized eggs can directly produce larvae after hatching and membrane release in 20~24 hours; The larvae grow rapidly, with an average length of 10.4 mm in the first larvae, and develop into juveniles in about 4 months.
The average adult length is 28.2 mm, and the largest individual can reach 48.7 mm; its weight is generally 15~45 grams, and the group size of spoon sturgeon in the breeding period is generally between 50~500; The population size in the spawning period can reach more than 2~30,000; In terms of growth rate, adults generally gain about 50% of their weight every two years.
Requirements for the breeding environment of spoon sturgeon
Spoonnose sturgeon is a very economically valuable freshwater fish, because of its strong reproductive ability, so the environmental requirements are higher, in the mainland, south of the Yangtze River is the main production area of spoon sturgeon, in the north of the Yangtze River can not naturally reproduce, only through artificial breeding can obtain spoon sturgeon.
The growth rate of spoon sturgeon is very fast, the maximum individual can reach 1~1.5 kg, but most of the spoon sturgeon has the characteristics of small individual, slow growth, poor disease resistance, low water quality requirements, and can adapt to the general freshwater aquaculture environment.
Spoon sturgeon belongs to cold-water fish, suitable for growth of 15~28 °C, the most suitable water temperature is 23~27 °C, more than 32 °C above can not grow normally, sensitive to water temperature changes, when the water temperature is higher than 10 °C to start feeding; Stop feeding when the water temperature is above 30°C.
The feeding and growth of the spoonnose sturgeon require sufficient dissolved oxygen, and it is generally believed that its breathing volume should reach 3 times the water weight in a suitable environment; When the dissolved oxygen is less than 4 mg/L, the spoon sturgeon has symptoms of hypoxia; When the dissolved oxygen is less than 2 mg/L, severe hypoxia will occur, and insufficient dissolved oxygen in the water can lead to the death of fish.
Water quality conditions are one of the important factors affecting the growth, development and reproduction of spoon sturgeon, because spoon sturgeon is an omnivorous fish, and its feeding is closely related to water temperature, special attention should be paid to the influence of water quality conditions and changes in food biomass on its growth, development and reproduction.
Spoon sturgeon is very sensitive to salinity changes, spoon sturgeon is a low-salt fish, the optimal salinity value is 18~20, can not tolerate more than 26 salinity.
Growth is slow and poor feeding when salinity is high, and feeding, growth and reproduction are inhibited when salinity increases. When salinity decreases, feeding and reproduction are improved. Therefore, special attention should be paid to controlling the change of salinity in the process of spoon sturgeon culture, and insufficient dissolved oxygen is one of the important causes of the death of spoon sturgeon.
The main link technology of the breeding stage of spoonnose sturgeon
Nursery pond conditions The nursery pond for cultivating fish fry requires sufficient water source, good water quality, a certain fertility, no industrial wastewater and domestic sewage inflow, the area of the nursery pond should be 5-10 mu, the water depth should be maintained at 0.5-1 meter, and the inlet and drainage are convenient.
In the process of fry cultivation, water source is a very important condition, and it is necessary to always pay attention to the changes in water quality indicators such as salinity, water temperature, dissolved oxygen, ammonia nitrogen and nitrite of the pool water, and take timely measures to prevent water quality deterioration.
The density of the fry cultivation stage should not exceed 1500 per mu, because the fry are small, so the growth space required is also small, so the cultivation density should not be too large; At the same time, in order to facilitate management and improve breeding efficiency, the cultivation density is required to be relatively small.
The seedling stage is mainly compound feed, and small-sized seedlings require that the feed protein content of daily feeding is more than 40%, and the feeding should be timed, fixed and quantitative, and the feeding amount should be 5%~10% of the fish body mass.
When the water temperature rises above 15 °C, fresh feed can be fed; When the water temperature reaches above 20 °C, compound feed can be fed, because the growth rate of spoon sturgeon is slow, so it is necessary to feed in separate ponds in time.
Dissolved oxygen is one of the most important conditions in the growth process of fry, sufficient dissolved oxygen will promote the rapid growth of fingerlings, and it is also necessary to pay attention to the changes in water quality indicators such as pH value, ammonia nitrogen concentration, nitrite concentration and so on in the pool water.
Generally, the water can be changed every 4-5 days on sunny days, and the water change is 1/3 of the pool water each time; in rainy days or hot weather, the number of water changes can be reduced or no water can be changed.
The specific treatment method is: put an appropriate amount of beneficial bacteria (EM bacteria, photosynthetic bacteria), EM original dew, biological enzymes and other biological agents or organic acids and other water quality improvers in the water body, the dosage of water quality improvers is generally 10 ppm ~ 20 ppm, and adjust the dosage in time according to the water quality.
Sturgeon is prone to the following diseases in the breeding process: water mold, enteritis, erythrotic disease, etc., disease prevention and control should be based on prevention, especially in the season of high water temperature and high temperature season should pay more attention to prevention, water mold is mainly caused by bacterial infection; Enteritis is mainly caused by malnutrition; Red body disease is mainly caused by nutritional deficiencies.
These diseases will adversely affect the growth and breeding of spoon sturgeon, so it should be prevented in time during the feeding process, and the fingerlings must be fed in separate ponds when they grow to a certain size, so that they can also avoid mutual cannibalism and food grabbing during the growth process.
When dividing the pool, the pool water should be drained first, and the pool water should be dried and disinfected before the pool dividing work; After dividing the pool, new water should be injected in time, and if the water quality is poor, the water should be changed in time.
After dividing the pool, the daily management should be strengthened, mainly including water quality monitoring, regular water change, disease prevention, observation of fish body changes, etc., and check whether the disinfection facilities are perfect before dividing the pool; Pay attention to the change of water temperature after dividing the pool, generally when the water temperature is higher than 15 °C, you can not divide the pool;
After dividing the pool, the water quality and water temperature changes should be monitored frequently, and measures should be taken in time once abnormalities are found; Pay attention to the changes in the fish body; Do a good job of daily inspection records.
The specific method is: when the water temperature is stable above 20 °C, the fish are scattered in the culture box for culture; When the fish grow to about 3 cm, the fish are gathered together for culture; When the fish grows to more than 4 cm, it can be directly put into the plastic cage prepared in advance for culture, and after being put into the cage, it is necessary to check whether the cage is damaged in time, and repair or replace it in time if it is damaged.
Development prospect of artificial breeding mode of spoonnose sturgeon
At present, the artificial culture mode of spoonnose sturgeon mainly includes cage culture, pond culture, factory culture and other modes, of which cage culture and factory culture are the two most common modes at present.
Cage culture refers to the setting up of one or more artificial fish nests in natural waters, in which large fish such as spoonnose sturgeon are placed for rearing, and when the fish reach a certain size, they are removed from the cage and divided and transported.
The history of artificial breeding of spoonnose sturgeon in the mainland can be traced back to the seventies of the last century, when the mainland is the only country in the world that can artificially cultivate spoonnose sturgeon, which has a history of nearly 50 years, but because the mainland has been in the traditional aquaculture mode, the research and utilization of large fish such as spoon sturgeon is not deep, resulting in the species is endangered in the mainland.
Since the eighties of the last century, the mainland began to establish large artificial fish nests in some natural waters and began to explore the artificial breeding technology of spoonstock sturgeon, but due to the long reproductive cycle, slow growth rate, small individuals and other factors of large fish such as spoonnose sturgeon, its population is not large.
In the nineties of the last century, due to a large number of fish diseases in the development of freshwater aquaculture in the southern region, resulting in a large number of deaths of large fish such as spoon sturgeon, some local aquaculture units chose to stock large fish such as spoon sturgeon as wild seeds in order to obtain more economic benefits.
However, due to the rapid decline in the number of this species, the depletion of resources and the serious pollution of the environment caused by overstocking, the current research and utilization of large fish such as spoonnose sturgeon in the mainland has not achieved the expected results.
The mainland is one of the world's largest producers of freshwater fish, with an average annual freshwater production of about 60 million tonnes, of which aquaculture production is about 50 million tonnes.
With the increasing prominence of socio-economic and population growth and environmental pollution caused by climate change, which has had a serious impact on the freshwater aquaculture industry, the development of freshwater fishery in mainland China mainly faces two major problems:
First, there are severe challenges in environmental protection and ecological protection in the freshwater aquaculture industry; Second, freshwater fishery resources are facing depletion, and some areas have experienced the decline or even depletion of freshwater fishery resources.
Therefore, how to protect and rationally utilize existing resources is one of the important issues facing the mainland at present, and some data show that there are more than 600 species of freshwater fish identified in the mainland, including some rare and endangered species, such as Chinese sturgeon and cochineal.
In the context of these precious and rare species if not properly protected and utilized, their populations will be sharply reduced or even extinct, and how to make full use of existing resources to develop the mainland freshwater aquaculture industry has become an urgent problem to be solved in the mainland aquaculture industry.
With the continuous strengthening of the management of freshwater aquaculture industry in the mainland and the continuous enhancement of people's awareness of ecological environmental protection, more and more attention has been paid to rare fish species, including large fish such as spoon sturgeon.
In recent years, the mainland has not only included large fish such as spoon sturgeon in the national aquatic germplasm resources protection plan, but also implemented strict management of them as key protection objects.
In order to promote the healthy and sustainable development of the mainland freshwater aquaculture industry, it is necessary to conduct in-depth research and exploration of the problems faced by large fish such as spoon sturgeon in artificial farming.
By studying and discussing the problems faced by large fish such as spoonnose sturgeon in artificial culture, it will be conducive to the healthy development of the mainland freshwater aquaculture industry and the protection of the ecological environment of waters.
conclusion
The distribution and habit characteristics, breeding patterns, disease control, disease research and nutritional requirements of the spoonstock are elaborated on the distribution and habit characteristics, breeding mode, disease prevention and control, disease research and nutritional requirements of the spoonnose sturgeon, in order to provide theoretical basis and technical support for the cultivation and seed cultivation of the spoonnose sturgeon, and promote the healthy development of the spoonnose sturgeon culture industry.
By elaborating on the distribution and habit characteristics, artificial breeding mode, disease control and nutritional requirements of spoon sturgeon, it is pointed out that there are still problems such as few seed source channels, slow growth rate and poor awareness of disease prevention in artificial breeding of spoonnose sturgeon.
Therefore, it is necessary to increase investment, improve the quality of seeds, develop appropriate feed formulas, strengthen research and prevention of diseases, etc., so as to improve the economic and social benefits of spoonnose sturgeon culture.
bibliography
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