Silver carp Hypophthalmichthys molitrix

Silver carp is an East Asian cyprinid of Pacific drainages from the Amur south to the Xi Jiang and northern Vietnam, farmed on a very large scale, with FAO FishStat recording 5,266,139 tonnes in 2024, and introduced widely for food and for algal control. Its defining structure is its feeding apparatus: the gill arches carry a filter fine enough to strain planktonic algae and organic particles down to about 0.02 mm, so from a few centimetres in length it lives on phytoplankton taken from the open water column and needs no compound feed. That niche is the whole argument for Chinese polyculture, where it is stocked with bighead carp on coarser zooplankton, grass carp on macrophytes and common carp on the benthos, each eating what the others cannot. FishBase gives a maximum of 120 cm total length, 50 kg and 20 years, with an environmental range of 6 to 30 degrees C. It spawns only in rivers with strong current, so it will not breed in ponds and hatcheries propagate it by induced spawning above 22 degrees C; maturity comes in the fifth or sixth year in temperate Europe but at two to three years in the tropics.