Hypophthalmichthys molitrix is one of the four Chinese major carps, together with H. nobilis, Ctenopharyngodon idella, and Mylopharyngodon piceus. This freshwater BENTHOPELAGIC fish naturally occurs in river systems in China and Russia and has been introduced into many countries for aquaculture purposes, despite its apparent great invasion potential and low market price. Together with H. nobilis, it is one of the most intensively cultured fish species in Asia, which is commonly raised in a system of 'harvesting and stocking', that is, stocking at a high density, partial harvesting of the larger FISHES, and the addition of new fingerlings. This Chinese carp, which prefers low flow but not stagnant waters, is commonly raised in polycultures in ponds, pens, reservoirs or lakes. As a plankton feeder, H. molitrix is frequently stocked in ponds for water quality enhancement and as a biocontrol method for phytoplankton. Competition with other species of similar feeding habits in polycultures is expected. H. molitrix is known for leaping out of the water when disturbed, and it naturally breeds during late spring and summer when the water level increases, migrating upstream to spawn. This carp is not able to spawn naturally in ponds or tanks, and its age and size at sexual maturity is apparently very variable and greatly affected by temperature, which means that it can be sold before reaching maturity. H. molitrix is usually kept alive from harvesting to marketing, as it is commonly consumed fresh, so that trucks and boats with water are frequently used as transportation tools. More studies about better slaughtering processes, stress response, and malformations on this species are needed, as well as studies about aggression both in wild and farm conditions. Furthermore, as most of the wild information comes from non-native waters research, more studies are still necessary in native waters.
