Rays are saltwater fish, while stingrays belong to freshwater fish; the size of adult rays is 50-800 centimeters, while the size of adult stingrays is 45-200 centimeters; the value of rays is mainly in the medicinal aspect, while the value of stingrays is mainly in the ornamental aspect.

The world's existing fish has been found in about 32,000 species, fish live in the water, distributed in the ocean and freshwater, living in the ocean accounted for two thirds of the rest live in fresh water. China counts two thousand five hundred species, of which more than a hundred species can be used for medicinal purposes.