Silver Carp Farming: A Production Guide

How silver carp (Hypophthalmichthys molitrix) is farmed: phytoplankton filter-feeding, role in polyculture, pond fertilization, hatchery induced spawning, growth and invasive-species caution.

Overview

Silver carp (Hypophthalmichthys molitrix) is a large filter-feeding cyprinid native to eastern Asia, from the Amur drainage south to the Xi Jiang. It is one of the highest-volume farmed freshwater fish in the world, second only to grass carp by weight, and is one of China's four famous domestic fish. It is grown almost entirely in pond polyculture, where it both produces food and helps manage water quality.

Biology and feeding

Silver carp is a filter feeder with fine gill structures that strain very small particles from the water; it feeds chiefly on phytoplankton and lacks a true stomach, feeding almost continuously. It grows quickly to a large size, commonly 60 to 100 cm and up to roughly 50 kg. Because it removes suspended algae, it is valued for controlling phytoplankton blooms, although some toxic cyanobacteria can pass through it.

Role in polyculture

In Chinese polyculture, silver carp occupies the phytoplankton niche in the upper water column. It is stocked with bighead carp, which takes the larger zooplankton, and with bottom- and vegetation-feeders such as common carp and grass carp, so the different species use different natural foods. Silver carp is often added to ponds where grass carp or other species fertilize the water, converting the resulting algal bloom into harvestable fish.

Pond fertilization and growth

Because silver carp depends on phytoplankton, ponds are fertilized with organic manure or inorganic fertilizer to sustain a dense algal bloom for the fish to filter. FAO integrated-farming guidance describes manuring ponds where silver carp is the major species to drive plankton production. With abundant plankton the fish grows rapidly to market size over a growing season or more, depending on temperature and stocking.

Reproduction and seed supply

Silver carp is a riverine spawner that does not reproduce in still ponds, so hatcheries produce fry by induced spawning. FAO records that induced spawning of silver carp and bighead in China dates to 1958, using injected common-carp pituitary and human chorionic gonadotropin (HCG); synthetic LRH-A is also used. Spawning is carried out in an optimum temperature range of about 22 to 28 °C, and fry are nursed to fingerling size before stocking.

Harvest and integrated farming

Silver carp is harvested by seining or by draining the pond, usually together with the other polyculture species. It fits well into integrated farming systems in which livestock or crop wastes fertilize the pond, turning agricultural by-products into fish through the plankton it filters.