What is the name of the cold current in Zhoushan Fishing Ground?

The Zhoushan fishery is located in the northern part of the East China Sea and the southeastern sea of ??the Yangtze Estuary. It is located outside the Qiantang River estuary and south of the Yangtze Estuary fishery. Its range is 29°30ˊ～31°00ˊN and the sea area to the west of 125°00ˊE, with an area of ??approximately 14,350 square meters. Square nautical miles

Physical environment The annual average surface water temperature is 16~20.1℃, the annual average surface salinity is 12.8~33.2, and the water depth is 2~70 meters

The hydrological environment includes the Yangtze River and Qiantang River The diluted water from the two major rivers is injected into it. The Kuroshio Warm Current passes through it in the east, the coastal water in northern Jiangsu and the cold water mass of the Yellow Sea extend southward in the north, the Taiwan Warm Current flows northward in the south, and the islands of the Zhoushan Archipelago system are distributed along the coast, which are rich in nutrient salts. , conducive to the reproduction of feed organisms

Taking the survey of nekton in Zhoushan fishery in July 1999 as an example, there were 43 species of nekton, of which hairtail accounted for 87.27%, Japanese mackerel accounted for 3.24%, spiny pomfret accounted for 2.58%, and small yellow croaker accounted for 2.03%, luminous sea bream accounted for 1.61%

According to the survey of zooplankton in Zhoushan fishery in October 1997, there were 141 species of zooplankton, among which 22.50% were daphnids and 22.50% were daphnia. Fleas accounted for 10.91%, Pacific spindle water fleas accounted for 6.75%, long-spined small thick-shelled water fleas accounted for 6.28%, and microspiny water fleas accounted for 4.94%.

The phytoplankton Zhoushan fishery was surveyed in July 1999. Example: There are 50 species of phytoplankton in ***, of which Rhizophora elongatus accounts for 61.88%, Chaetoceros lowlandii accounts for 15.33%, Trachophyton mediterranea accounts for 6.54%, Chaetoceros stenostoides accounts for 4.22%, and Chaetoceros pseudofidus accounts for 4.22%. Hair algae accounted for 3.21%

Benthos Zhoushan fishery took the survey in January 2000 as an example. There were 76 species of benthic organisms, with high-skeletal sandgrouse accounting for 23.53%, eagle claw shrimp accounting for 12.95%, and Onu Philippine worms account for 7.24%, white snout silkworms account for 5.14%, and Japanese beauty shrimps account for 4.14%

The main fishing objects are hairtail, small yellow croaker, large yellow croaker, green fin pufferfish, white croaker, pomfret, Mackerel, blue-spotted mackerel, mackerel, trevally, jellyfish, squid, Pacific tuna, swimming crab, round-toed crab and shrimp, etc.

The main fishing season is from November to January of the following year

The fishery is a spawning and feeding place for many economic fish and shrimps. It is the largest and most productive hairtail fishery for mass fisheries along my country's coastal winter. It is a good area for bottom trawling operations and has become the most famous fishery in the country. Important types of operations in this sea area include light seines, gill nets and sail nets, etc.

Introduction to the fishery

The Zhoushan fishery is the largest offshore fishery in my country, similar to the Hokkaido fishery in Japan. , Canada’s Newfoundland fishery, and Peru’s Peruvian fishery are equally famous. Fishermen are accustomed to dividing Zhoushan fisheries into Daji fisheries, Shengshan fisheries, Langgang fisheries, Huangze fisheries, Daiqu fisheries, Zhongjieshan fisheries, Yang'an fisheries and Jintang fisheries according to each operating sea area.

Since its development, Zhoushan Fishing Ground has been the first fishing place for coastal fishermen. Since liberation, the number of fishing boats coming to Zhoushan fishery from Zhejiang, Jiangsu, Fujian and Shanghai (referred to as "three provinces and one city") has been increasing. Some fishing boats from Liaoning, Hebei, Shandong, Tianjin and other provinces and cities also came to Zhoushan fishery for a time. In the 1960s and 1970s, fishing boats gathered at the Shengshan fishery to catch winter hairtail. At the peak of the flood season, there were 10,000 fishing boats and more than 150,000 fishermen.

Geographical location: Zhoushan Fishing Ground is located at 29°3O′～31°OO′ north latitude and 121°3O′～125°00′ east longitude. It is connected to Zhouwai Fishing Ground to the east, Yushan Fishing Ground to the south, and the Yangtze River to the north. The fishing ground covers an area of ??about 53,000 square kilometers. The seafloor is dominated by a mixture of fine-grained sediments such as silt and clay ooze, and is a component of the East China Sea continental shelf. The water depth is generally 20 to 40 meters. The distance from the 80-meter isobath from north to south is 280 to 150 kilometers from the shore.

Hydrological elements The Zhoushan Fishing Ground is located at the estuary of the Yangtze River, Qiantang River and Yongjiang River, where the coastal current, Taiwan Warm Current and Yellow Sea cold water mass meet. On average, nearly 1 trillion cubic meters of mainland water flow into the sea every year, forming a strong low-salt water mass with turbid water color that stretches outward in spring and summer and retreats toward the coast in autumn and winter. The Taiwan Warm Current has high temperatures, high salinity, and clear water color. It wedges from south to north in spring and summer and reaches the coastal waters. In winter, it deviates from the coast and retreats to the south. The cold water mass of the Yellow Sea moves southward, and as the strength of the Taiwan Warm Current changes, it extends into the fishing grounds like a tongue in autumn and winter, and gradually retreats northward in early summer, forming a meandering water mass mixing zone in the north and south. The tidal current of the fishing ground belongs to the regular semi-diurnal tidal area. In the east sea area connecting the outer islands, the flow direction is a clockwise rotation flow. In the west sea area, the islands are arranged and the reciprocating flow is prominent. The water temperature in the fishing ground is the highest monthly average of 28°C to 29°C in the surface layer in summer and below 8°C in winter. The salinity of the fishery is average monthly at 29-34‰ in the outer sea area. Due to the influence of the continental Jing current, the inner sea area changes greatly, with low values ??in summer and high values ??in winter.

Biological resources The continuous flow of rivers and streams in the mainland brings a large amount of plankton to the fishing grounds, which combines with seawater nutrients and salts to promote their rapid growth and reproduction. The phosphorus and silicon contents in offshore fisheries are 30-40 mg/cubic meter and 2000-3000 mg/cubic meter respectively. There are 151 species of phytoplankton in shallow sea waters, of which planktonic diatoms account for more than 90%. The annual average phytoplankton content in the water body is 107×104/cubic meter, with high levels in summer and low levels in winter.

There are 123 species of zooplankton, with an average annual content of 87.7 mg/cubic meter and a maximum of 1,633 mg/cubic meter in summer.

The superior natural conditions such as geography, hydrology, and biology make the Zhoushan fishery and its surrounding waters a habitat suitable for the reproduction, growth, feeding, and overwintering of a variety of fish. Among them, large yellow croaker, small yellow croaker, hairtail and squid are the resource groups with the largest catch in Zhoushan fisheries, and are known as the "four major fish products".

Main fishing floods From the beginning of this century to the late 1970s, there were small yellow croaker floods in spring, large yellow croaker and cuttlefish floods in summer, jellyfish floods in autumn, and hairtail floods in winter. With a large number of motor boats put into production all year round, there is no clear limit to the fishing season.

Since the 1980s, fishing seasons for small yellow croaker, large yellow croaker, squid, and jellyfish have ceased to exist. The hairtail fish season has also seen a decline in prosperity and a decline in net catches