Pseudosciaena polyactis is a fish belonging to the genus Pseudosciacna of the family Sciaenidae. This fish, which lives entirely in the ocean, is often divided into multiple populations when migrating. The migration routes of each population are different, and they will not mix. Usually during the breeding season, they swim in groups to the coastal waters of islands or inner bays, and to the deep sea in autumn and winter.
Salmon is a cold-water anadromous fish. They usually live in the ocean, but when it comes to breeding season, they will travel upstream to the middle and upper reaches of rivers. It is worth mentioning that this fish has a certain adaptability to salinity, usually does not feed during retrograde migration, and will die directly after spawning.
Eels are also migratory, but their migratory route is just the opposite of that of salmon. They live in fresh water most of the time, and when they reach the breeding season, they will swim to the ocean to spawn. Like salmon, they do not feed when they migrate, and after spawning, the parents die and the young return to freshwater.
Not only grass carp, in fact, the four major Chinese carps all have the characteristics of migration. Although they live entirely in fresh water, sometimes they often swim from one type of water body to another type of water body. Therefore, they are also called semi-migratory fish. The reason for migration, in addition to breeding, may also be due to the need to overwinter.
