Fish stocking is the practice of raising fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 in a hatchery

Fish hatchery

A fish hatchery is a "place for artificial breeding, hatching and rearing through the early life stages of animals, finfish and shellfish in particular". Hatcheries produce larval and juvenile fish primarily to support the aquaculture industry where they are transferred to on-growing systems...

 and releasing them into a river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

, lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

, or the ocean

Ocean

An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...

 to supplement existing populations, or to create a population where none exists. Stocking may be done for the benefit of commercial, recreational, or tribal fishing

Fishing

Fishing is the activity of trying to catch wild fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....

, but may also be done to restore or increase a population of threatened

Threatened species

Threatened species are any speciesg animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future.The World Conservation Union is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories,...

 or endangered

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 fish in a body of water closed to fishing.

In the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, common species that are stocked for sport include trout

Trout

Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...

, muskellunge

Muskellunge

A muskellunge , also known as a muskelunge, muscallonge, milliganong, or maskinonge , is a large, relatively uncommon freshwater fish of North America. Muskellunge are the largest member of the pike family, Esocidae...

, walleye

Walleye

Walleye is a freshwater perciform fish native to most of Canada and to the northern United States. It is a North American close relative of the European pikeperch...

, and several species of panfish

Panfish

A panfish, also spelled pan-fish or pan fish, is an edible game fish that usually doesn't outgrow the size of a frying pan. The term is also commonly used by anglers to refer to any small catch that will fit in a pan, but is large enough to be legal. However its definition and usage varies with...

. Fish stocking may be done by governmental agencies in public waters, or by private groups in private waters.