In order to verify the common knowledge about the growth of cold water masses and shrimp scallops, a reporter from Securities Times contacted Professor Fang Jianguang, a marine ecologist at the Yellow Sea Institute of Oceanography, Chinese Academy of Fishery Sciences. Related issues are described. The following is the full text of the article written by Professor Fang Jianguang.
1. What is the North Yellow Sea Cold Water Mass?
The Yellow Sea is a semi-enclosed continental shelf shallow sea. The most prominent feature of its submarine topography is that there is a northwest-southeast-trending Yellow Sea deep trough in the central part of the South Yellow Sea, with a water depth of about 50-80m, and the trough gradually becomes shallower after entering the North Yellow Sea. Go east-west. Existing studies have pointed out that geographical features such as the deep trough of the Yellow Sea and its east-west asymmetry play an important role in the formation and evolution of hydrodynamic environments such as the Yellow Sea cold water mass and the Yellow Sea warm current. The Yellow Sea is divided into North and South Yellow Sea by the line connecting Chengshantou of Shandong Peninsula of my country and Changshan of North Korea (193km wide). The North Yellow Sea is located in the Shandong Peninsula, between the Liaodong Peninsula and the Korean Peninsula. The west side is connected to the Bohai Sea through the Bohai Strait, and the south side is connected to the South Yellow Sea. The average water depth is only 38m. One of the most striking hydrological features of the North Yellow Sea is the distribution and evolution of the cold water mass in the Yellow Sea. In summer, there is always a low-temperature isolated water body above the depression of the North Yellow Sea; The range of degree variation is usually about 31.8 to 32.5. This large temperature difference, small salinity difference, is mainly characterized by low temperature, and has a low temperature water body that is almost constant for a long time, and is called the "North Yellow Sea Cold Water Mass".
Key points: Because the coast of the North Yellow Sea is shallow and the middle seafloor is in the shape of a trough, the low-temperature water on the surface in winter descends into the trough through vertical mixing. After warming up in spring until summer, the surface temperature of the ocean trough is high and the bottom temperature is low, and vertical mixing cannot be formed. Therefore, the low-temperature water formed in winter is still stored in the ocean trough, thus forming a cold water mass. The temperature of the surface water was lower than that of the bottom layer from autumn to winter, and through vertical mixing, the low-temperature seawater began to sink into the ocean trough again, and the cold water mass gradually disappeared.
2. Is the distribution range of the North Yellow Sea cold water mass unchanged, or is there an annual change?
Song Xin from Ocean University of China et al. (Journal of Guangdong Ocean University, 2009. Vol.29 No.3) conducted an observational analysis of the interannual variation data of the Yellow Sea cold water mass. The directional and zonal wind speeds are related, and the larger the wind speed, the larger the range. Therefore, the variation of the Yellow Sea cold water mass has obvious annual variation characteristics, and its distribution range is very different even in the adjacent two years. That is to say, the distribution range of the cold water mass in the North Yellow Sea is not static, but varies from year to year, which is positively correlated with the wind speed in winter.
Key points: The distribution range of cold water masses varies with natural factors such as winter weather, covering a large area in some years and a small area in some years.
3. Does the cold water mass in the North Yellow Sea have seasonal changes?
Yao Zhigang et al. analyzed the distribution and seasonal changes of the North Yellow Sea cold water mass in the article "Analysis of Seasonal Variation Characteristics of the North Yellow Sea Cold Water Mass" published in the Journal of Ocean University of China (Natural Science Edition) in 2012. In winter, the cold water mass in the North Yellow Sea disappears; in spring, the cold water feature in the central part of the North Yellow Sea begins to appear. The cold water at 6°C covers the range of 38.0-38.8o north latitude and 121-123o east longitude, and the salinity in the center of the cold water is greater than 32‰; in summer, The cold water mass in the North Yellow Sea is completely formed, and the minimum temperature is about 6 °C. An obvious front is formed between the cold water mass and the high temperature and low salt water on the shore; in autumn, the strength of the cold water mass in the North Yellow Sea is weakened, and there are two low temperature centers of 9 °C and high salt centers. Still located near 38.5o north latitude and 122.5o east longitude. It can be seen from this that the cold water mass in the North Yellow Sea has obvious seasonal changes, and is the strongest in summer.
Key points: The seasonal changes of the cold water mass in the North Yellow Sea are very obvious, and the most obvious in summer. At the same time, due to the influence of bad weather, such as typhoons, the coverage of the cold water mass in the North Yellow Sea also varies greatly in the same season.
4. Can the annual variation of the distribution range of the North Yellow Sea cold water mass be predicted?
Although some scholars have used physical ocean models to try to predict the annual changes of the North Yellow Sea cold water mass, they have not yet reached the level of accurate prediction. Currently being explored.
5. The ecological habits and introduction time of Ezo scallops?
Ezo scallops are native to Japan, the southern waters of the Kuril Islands of Russia, Hokkaido, Japan, and northern Honshu, and are large cold-water shellfish.
Ezo scallops are distributed on the bottom of the sea with hard bottom and less silt. The natural distribution water depth is 6-60m, the growth temperature range is 5-20°C, and the optimum growth temperature is around 15°C. The growth is slow below 5°C, and the movement slows down sharply until it stops at 0°C; when the water temperature rises to 23°C The ability to live gradually weakens, and the movement will soon stagnate after the temperature exceeds 25 °C. Ezo scallops are a high-salt species, with a suitable salt range of 24-40. According to records, the maximum shell height of Ezo scallop can reach 27.94 cm, and its life span is about 25 years.
From 1980 to 1982, Liaoning Provincial Institute of Marine and Fisheries introduced the parent scallop scallop from Japan for four times, and the artificial seedlings were successfully raised. The main breeding areas are distributed in the Liaodong Peninsula, Shandong Changdao and other sea areas in northern my country.
7. Is there a direct relationship between the large-scale death of bottom-seeded scallops and the temperature fluctuation of the cold water mass in the North Yellow Sea?
The Changshan Islands in Liaoning Province is the main sea area for breeding scallops in my country. However, since the 1980s, a large number of farmed scallops died in this sea area in summer, resulting in many disasters and major economic losses. Domestic scholars such as Zhou Wei and Wang Xihou have analyzed the hydrological environment and scallop mortality in aquaculture areas from the perspective of water temperature fluctuations. Zhang Mingming, Zhao Wen, etc. published a paper entitled "Discussion on the Causes of Death of Ezo Scallops in my country and Control Measures". (China Aquatic Products, 2008, 2: 64-74). Zhou Wei, Xue Zhenfu, Wang Youjun, etc. published "The relationship between abnormal fluctuation of water temperature in the sea area of Ocean Island and the death of cultivated scallops." (Ocean Limnology Bulletin, 1992, 4:56-62). Relevant studies have confirmed that the cold water mass in the North Yellow Sea is an important physical ocean factor affecting the sea area, and it is the macro environment formed by the thermocline and water temperature fluctuations. The death of Ezo scallops was associated with abnormal fluctuations in water temperature. .
8. Does the temperature fluctuation of the cold water mass in the North Yellow Sea affect the physiological metabolism of scallops?
Xu Dong et al. used indoor controlled experiments to study the effects of rapid temperature increase and slow temperature change on the oxygen consumption rate and ammonia excretion rate of scallops and their differences. In the experiment, two temperature treatment methods were set, namely, the temperature sudden change group) and the temperature slow change group. The results show that drastic changes in water temperature can lead to abnormal metabolism of shellfish, and scallops consume more energy. It shows that the scallop is relatively sensitive to temperature, and its ability to cope with severe temperature changes is weak. Frequent alternation of warming and cooling may have a greater impact on scallops (Xu Dong, Zhang Jihong, Wang Wenqi et al. Effects of temperature changes on oxygen consumption and ammonia excretion rates of scallops, China Fisheries Science, 2010, 17(5): 1101-1106 .).)
Key points: Temperature changes, especially sudden changes in temperature, significantly affect the physiological state of scallops. Sudden increases in temperature, especially in the high temperature range, can affect the survival of scallops.
1. Strengthen the long-term and continuous monitoring of physical, chemical, biological and other factors in the adjacent North Yellow Sea cold water mass, and provide basic data for the prediction and forecast of the impact of the North Yellow Sea cold water mass on the breeding of scallops.
2. Evaluate the capacity of the scallops in the North Yellow Sea to increase the breeding capacity, so as to determine the scientific and reasonable breeding density, layout and structure.
3. According to the maximum distribution range of the cold water mass in the North Yellow Sea in summer, determine the southern limit of the sea area for scallop growth and scallop growth, and leave a certain isolation zone between the cold water mass and the growth area for scallop growth.
4. Strengthen international cooperation, learn from foreign marine aquaculture management decision-making systems, and implement ecosystem-level aquaculture management.
(Note: The opinions of experts in the article only represent my own opinions, not the position of the institution where they work)