Lake knife VS river knife
Every year in the lunar calendar in beginning of spring, it is the time for saury breeding season. Saury goes upstream from the Yangtze estuary and lays eggs in the main stream, tributaries and affiliated lakes in the middle and lower reaches of the Yangtze River. The swordfish caught in the Yangtze River is called river knife; Some swordfish have settled in Tongjiang Lake in the middle and lower reaches of the Yangtze River. Influenced by the ecological environment, they have differentiated from Jiangdao into a group with obvious differences in ecology and reproduction, which is called Lake Knife. Some swordfish, due to environmental or genetic factors, have matured in offshore gonads and do not migrate. They are also obviously different from river knives in ecology and reproduction, so they are called sea knives. Sea knife and lake knife are two ecotypes of swordfish. "Simply put, they are swordfish, but they are different from river knives." Shiping Li, an associate professor at the College of Biological Sciences and Technology of Yangzhou University, explained.
Compared with the river knife, the mature age of the lake knife is earlier, and the parent fish (fertile females and males) of the river knife are shorter and less thick than the river knife. Lake Dao does not migrate, and its fat content is lower than that of river Dao, so it is not as delicious as river Dao.
Sea knife VS river knife
The gonad of the sea knife has matured in the offshore, and the gonad began to develop after the river knife moved to the Yangtze River. The maturation of gonads needs to consume a lot of fat. In the process of migration, the crude fat content in the nutrients of river swordfish is obviously higher than that of sea knife, which is twice as high as that of sea knife. However, the moisture, crude protein and ash are lower than those of sea knife, so river knife is more fragrant than sea knife. Moreover, the absolute contents of arachidonic acid and docosahexaenoic acid (both commonly known as "brain gold") in Dao Jiang are significantly higher than those in the islands. "This is also the reason why Jiangdao's' Immature Fragrant Nose Drives'."
The research shows that when Jiang Dao moved to Jiangyin section of the Yangtze River, he only removed the salt and lost a little astringency. "It is precisely because of water, bait, heredity and other factors that although they are all swordfish, the tastes of the three swordfish are different." Shiping Li said.
River knives are delicious, but this does not mean that river knives are richer in nutrition than sea knives. In fact, the hydrolyzed amino acid composition of saury and saury is basically the same, both of which contain 18 amino acids. The proportion of some amino acids in saury is higher than that of saury, some are higher than that of saury and some are basically the same. "It can only be said that both sea knives and river knives are high-quality fish with high nutritional value."
Fish is rich in protein, which can help children grow and develop. When you are sick or have a wound, eating fish helps to recover and heal; EPA and DHA in fish can reduce blood lipid and avoid the threat of heart disease. Fish oil is also rich in vitamins A and D, especially in the liver of fish. Fish also contains water-soluble vitamin B6, B 12, nicotinic acid, biotin and minerals.