Hatcheries provide the seed for aquaculture and some commercial fisheries. All kinds of fish and shellfish begin life in tanks in a hatchery. A hatchery is a mix of a laboratory and a farm, where fish and shellfish are spawned, then hatched and cared for. They remain at the hatchery until they are large enough to be transferred to a fish or shellfish farm or released into the wild as part of a stock enhancement program. Commercial fish and shellfish farms require a steady, predictable source of juveniles from hatcheries in order to stay in operation and provide a consistent product.

Hatcheries are also used for stock enhancement—also known as 'restoration aquaculture'—through which fish and shellfish are raised in a hatchery and then released to supplement the populations of recreational, commercial, and ecologically-important species.