In China's coastal areas, Shijiugong is a relatively common small seawater fish, commonly known as tiger head fish, stone fish, stone perch, etc., and the biological name is Sebastiscus marmoratus. Because of its tender and delicious meat, Shijiugong is also known as the "little grouper" and is quite popular in high-end hotels and restaurants.
Shi Jiugong /Brown Calamus
Shi JiuGong is very suitable for steaming and boiling soup, the taste is very delicious, but even so, Shi JiuGong has not become a mainstream aquatic product like pomfret and sea bass, the main reason is that it is difficult to catch, natural production is low, and the size is also very small.
In the natural environment, Shijiugong mainly inhabits the reef area by the sea, feeding on small fish, shrimp and crabs, wheat straw insects, mud snails, etc. Adult Shijiu is between 10 and 20 centimeters long and weighs 50 to 300 grams, making it a suitable small fish.
The catch of Shi Jiugong
Due to the inconvenience of large-scale fishing operations in the reef area, fishermen generally do not target Shijiugong as their catch. If you want to capture Shi Jiugong, the general method is sea fishing or longline fishing, and you can also try to trap with a cage, but the yield cannot be guaranteed, and how much you can catch in the end depends on luck.
In addition to the coastal waters of China, Shi Jiugong is also distributed in Japan, North Korea and other places, and it is also a famous and valuable seafood overseas. In the 1970s, Japan took the lead in conducting systematic biological research on Shijiugong, and also successfully broke through artificial breeding technology, and has now achieved large-scale breeding.
Ishikuko in the Japanese aquatic market
From the perspective of nutritional value and market conditions, Shijiugong has the potential to develop as a farmed species, as long as the output can be increased, considerable industrial benefits can be created. In order to develop and utilize this biological resource, China's older generation of aquatic experts began to investigate the resources of Shijiugong along the coast in the 1960s, and found that the East China Sea and the South China Sea are the main distribution areas of Shijiugong, and the amount of resources is considerable.
According to the records, around 1966, there were a large number of Shijiugong resources in the fishing grounds of Zhongshan Street Archipelago in Zhejiang, but due to the gradual increase in the fishing intensity of hand fishing and longline fishing, the resources of wild Shijiugong were gradually reduced. By the early 1980s, small fishing boats along the coast began to transform into squid fishing (one of the four seafood in China), hand fishing and longline fishing vessels began to decrease, Shi Jiugong was given the opportunity to recuperate, and resources began to gradually rise again.
Squid fishing industry offshore
According to the memories of old fishermen around Dongting Mountain, Beiting Mountain and Dongfu Mountain, in the past, from January to March every year, they could catch up to 100 kilograms of Shijiugong per day, and the market price was more expensive than grouper. By April-June, Shijiugong's production began to decrease, and each fishing boat could generally catch about 10-20 kilograms, and if it was lucky, it could catch 50 kilograms.
Little Stone Nine Gong in the mesh
Fishing alone is not a long-term solution, and it is difficult to meet market demand. In terms of efficiency, the harvesting of wild Shijiugong is far inferior to artificial farming, which has a more stable yield and meets the needs of commercialization.
Around 2008, the domestic research team tried to cultivate Shijiugong in offshore cages, and all the fry were caught in cages, avoiding the physical damage of fishing. In order to improve the survival rate, the farmers also further screened out healthy seedlings with robust physique and no damage to appearance, and all the seedlings were sterilized with potassium permanganate before being put into cages.
Fish steaks and cages in the Sanduao Sea area
The site of the test was selected in the Sanduao Sea District of Ningde City, Fujian Province, which is a famous yellow croaker production area with excellent water quality and abundant bait. The transparency of the seawater in the breeding area is about 0.5 to 0.8 meters, and the content of dissolved oxygen is more than 6 mg/l all year round, which provide excellent natural conditions for the cultivation of Shijiugong.
However, in the early stage of breeding, Shi Jiugong's feeding was not active, and even if sufficient bait was put in, it would not be eaten immediately. Later, after a period of domestication of food habits, Shi Jiugong began to eat normally, and the growth rate gradually accelerated.
According to statistics, the initial weight of this batch of seedlings is 23 grams, after 150 days of breeding, the weight of Shi Jiugong increased to 44 to 53 grams; after 300 days of artificial breeding, most individuals weighed 71 to 87 grams; after one year of breeding, the weight of Shi Jiugong reached 85 to 104 grams, at which time it can start to catch and market.
Growth curve of Shijiugong under monoculture and polyculture modes
Interestingly, if Shijiugong and Yellow Croaker are polycultured together, the growth rate is faster than that of single culture (you can refer to the growth curve in the figure above), and the survival rate can reach 72.8% - while in the case of single culture, the survival rate of Shijiugong is only 67.1%.
Therefore, the most feasible way is to take the yellow croaker as the main fish farming, and the Shijiugong as the fish breeding, the main and secondary combinations can not only make full use of the bait resources and water space, but also save time and cost, and improve economic benefits. For farmers, while breeding mainstream marine fish such as yellow croaker, some Shijiu gong seed can be released by the way, which is easy to operate, saves trouble and worry, and has a lot of success in one fell swoop.
Therefore, the most cost-effective way to achieve high production is artificial farming (rather than fishing) - but the problem is that at this stage, the domestic farming technology is not particularly mature, the cost of breeding is still very high, and it is not suitable for large-scale promotion.
Shi Jiugong died during the breeding process
Especially from June to September every year, excessive sea temperatures often lead to a spike in Shijiugong's mortality rate. When the water temperature is higher than 26 ° C, Shi Jiugong is prone to enteritis, and the symptoms of white eyes and festering fins occur from time to time, and even healthy fish will have a significant reduction in feeding rate.
Compared with the above unfavorable factors, the most "stuck neck" problem is artificial breeding technology. The inability to break through artificial breeding technology means that a large number of seedlings cannot be obtained, and it is impossible to artificially breed.
Unlike other fish, Shijiugong's breeding method is oviparous birth – fertilized eggs hatch in the mother's body and are produced outside the body when the body length of the larvae reaches 3.5 to 4.2 mm. A large Shijiugong weighing 300 to 400 grams can give birth to 30,000 to 50,000 calves, which is already considered "high yield" for oviparous fish.
Artificially bred Shijiu broodstock (for breeding offspring)
The breeding method of this fish is relatively special, and the artificial breeding technology of Shijiugong has not been conquered in China for a long time, and it has only achieved certain results in recent years. In 2018, the staff of the Shanghai Fisheries Research Institute successfully bred more than 300,000 Shijiugong seedlings, and the commercial development of this species has taken a big step forward.
Our researchers spend so much time and energy on this fish, but not just to develop it into a food fish. In addition to having a high edible value, Shijiugong itself is also a good sport fishing species, which can be developed as a target fish species for the marine fishing industry, which is also a new project in China. As a resource support for the sport fishing industry, it is possible to release the seeds of Shijiugong in a specific reef area by artificial breeding, and the commercial potential is huge.
Therefore, in the future, Shijiugong is likely to be developed into a new commercial fish species, and artificial breeding may become the mainstream "harvesting" method. We'll see!