Seedlings migration rules and fishing experience

Aquatic treasures, fresh and delicious, rich in nutrients, and rich in economic value, is a world-wide cultured fish. Japan, which has a particularly developed aquaculture industry, has an annual output of 2 million tons of salmon, which accounts for half of world production. Hemorrhoids is a migratory fish that grows in fresh water and reproduces in seawater. They live in fresh water for 5 to 8 years and begin sexual maturity. In the reproductive organs, they secrete a hormone that stimulates them to spawn and swim. Whenever rainy nights, sexually mature females enter the sea along rivers and rivers, once discovered When they enter the sea, they will be blocked. They will search in groups and find another outlet. The spawning and hatching are all in the depth of 400 to 500 meters. The temperature is 16 to 17 degrees Celsius. Females do not feed during the spawning period, and one female can lay 7 to 13 million eggs. After spawning, female spawning migratory trips are terminated, which means females die in seawater. Young seedlings hatched from eggs are silver-whisker and feed mainly on zooplankton. When they grow up, they eat aquatic insects, and they also eat small fish and shrimp. During the day in the 30m water layer, it moves on the surface in the evening. In the ocean, it may be drifting through the river for a year. It is rushed to the coastal coast of the land by the seawater, and turns into a slender, transparent cub near the gate of the river. From December each year to May next year, the young birds enter the river upstream, and most areas have the largest amount of rivers from the end of January to the beginning of March. The seedlings advancing to the river at night, that is, the sunset began to move, when the tide rises, it is up to the river. In the latter part of the river, the pigment of the seedlings increases, turning from white to black and turning into black seedlings. Seedlings harvested in late May are still mixed with white seedlings, but black seedlings account for the majority. June was the season when black seedlings came to the river. The black seedlings decreased from late July to August, and until the fall, there were still a small number of young fishes that crossed the river. Transparent seedlings just after the river, full-length 4.6 cm ~ 6.6 cm, weight 0.15 g, seedlings dived into the sand mud in the sea during the day and swim to the river at night, when the environment is appropriate, it will flow upstream, into the rivers. The seedlings are very sensitive to the fresh water and are stimulated by fresh water during the flood season. They flood into the vicinity of the sluice at the mouth of the river where the brackish water meets. They lead to a fishing season and the fishermen go fishing. Seedlings are concentrated in places where fresh water rushes. They are frightened by light and are afraid of strong light. There are more uptakes at night than in the daytime, especially when it is 2 to 4 hours after sunset. The amount of seedlings advancing upstream is closely related to the tide, and the tide is more than the tidal wave, and the high tide is more than the ebb tide. The number of seedlings increased with the increase, and the tide increased to 78% to full tide, and the ebb tide gradually decreased. Seedlings in the river are better off with no wind and breeze, and strong winds affect the elevation and fishing. In floodgates with large fresh water flow, seedlings also have large quantities. There is also a relationship between the upstream and the temperature. The optimum temperature for the upstream is 14°C. When the water temperature is below 10°C, the amount of the river is less, and the seedlings below 6°C lurk on the sea floor. Can master the law of seedling migration, seedlings can be caught. At present, seedlings are in short supply in the international market. Seedlings are as expensive as gold. Harvesting seedlings is a way to create foreign exchange for the country and fishermen toward prosperity.