Fish, like goose, can be used as a synonym for letters. In order to convey secret information, the ancients wrote letters on silk and put them in the belly of fish. In this way, using fish to convey messages is called "fish conveying ruler elements". During the Tang and Song Dynasties, dignitaries and dignitaries all wore gold letter talismans called "fish talismans" to indicate their status. "Fish" and "yu" are homophonic, so fish symbolizes wealth. "Like a fish in water" is used to describe harmony, happiness and freedom between work and life.

Extended information

The lives of fish are diverse. Most fish live either in fresh water or sea water. Only less than 10% of fish spend part of their time in the ocean. They spend part of their time in fresh water and migrate back and forth between the two habitats, which is called migration. If it grows in the ocean but needs to go to fresh water to breed, it is called anadromous migration (such as the Chinese sturgeon). If it grows in fresh water but needs to go to the ocean to breed, it is called anadromous migration (such as the flower eel).

If the migration of fattening and breeding occurs between rivers and lakes, it is called semi-migratory fish. They usually fatten in lakes and lay eggs in rivers (such as the four major fishes). There are also some fish whose lives are limited to the main branches of rivers and only migrate relatively short distances.

There are many reasons for fish migration, the first of which is affected by external conditions. Fish live in water, and their activities are affected by factors such as temperature, current, and salinity. But migration is mostly caused by changes in water temperature. When the water temperature changes, fish will look for a suitable living environment and migrate. Because the lateral line receptors on both sides of their bodies are particularly sensitive to the stimulation of water flow, they can help fish determine the speed and direction of water flow.

Reference: Fish_Baidu Encyclopedia