Most of China is located in temperate or subtropical zone, with mild climate and abundant rainfall, which is suitable for fish growth. It has excellent fish culture techniques such as grass carp, silver carp, bighead carp, herring, bream, carp, crucian carp and bream. It is the most developed country in the world today, and it ranks in the leading position in the world in terms of aquaculture area and total output.
The digestive system of fish consists of digestive tract and digestive gland. The digestive tract has gastrointestinal differentiation, and the pancreas is obvious. Fish live in water all their lives, so their digestive organs and feeding habits are adapted to life in water.
Extended data:
Fish live in various ways. Most fish live in fresh water or seawater. Less than 65,438+00% of fish spend part of their time in the ocean and the other part in fresh water. They migrate back and forth between two habitats, which is called migration.
If it grows in the ocean but needs to breed in fresh water, it is called upstream migration (such as Chinese sturgeon), and if it grows in fresh water but needs to breed in the ocean, it is called downstream migration (such as eel).
If the fattening and breeding migration occurs between rivers and lakes, it is called semi-migratory fish, usually fattening in lakes and laying eggs in rivers (such as the four major fish). There are also some fish, whose life is limited to the main tributaries of the river and they only migrate for a relatively short distance.