Sea catfish, also known as chubby-headed fish, is a kind of offshore bottom fish, which usually inhabits the sea area with a water depth of 40 ~ 60 meters and crawls on the seabed without long-distance migration.
Catfish is slender, with a wide and flat front and a flat back, about 50 cm long. The back is bluish gray, the abdomen is white, the mouth is big and inferior, and there are three pairs of whiskers. Scaleless dorsal fin and pectoral fin are hard spines, ventral fin is short and caudal fin is bifurcated. Habitat in tropical and subtropical coastal bottom, staple food invertebrates and small fish.
Sea catfish live in the southeast coast of China and other waters. Both boat fishing and rock fishing can be done, with animal bait.
Extended data
Saltwater fish and freshwater fish
According to the water environment system in which fish live, they can be divided into freshwater fish and saltwater fish. Freshwater fish live in fresh water of rivers, lakes and seas all their lives, while saltwater fish live in the sea of Wang Yang all their lives. Generally speaking, the salinity of Shanghai water on earth is generally 35%, while that of fresh water is only about 0.3%.
The salt concentration in the body tissues of saltwater fish is much lower than that in the surrounding environment where they live. Seawater contains a lot of high-density salt, and the osmotic pressure of fish body fluids is lower than the surrounding water environment. According to the osmotic pressure principle, the water in the body tissues of saltwater fish will continuously seep from gills and body surfaces. In order to keep the water balance in the body, saltwater fish must constantly swallow a lot of seawater to make up for the loss of water in the body.
Freshwater fish are very different from saltwater fish. The salt concentration in freshwater fish body tissues is higher than that in living environment. Fresh water has low salt content and low density. According to the osmotic pressure principle, fresh water from the outside will continue to enter freshwater fish, and freshwater fish must excrete excess water through the kidneys.
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