Stocking Lakes with Fish

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Fishing is a popular pastime, and the practice of stocking lakes with fish to catch is popular, too. Organizations that manage natural resources add fish to lakes and streams to make fishing more fun for anglers. It can provide sport fishers with fish that are big enough to keep, and sometimes fish that are big enough to be considered trophy-sized.  Rainbow trout (Oncorhyncus mykiss), walleye (Stizostedion vitreum), Atlantic salmon (Salmo salar), northern pike (Exox lucius), blue gill (Lepomis macrochirus), and muskellunge (Esox masquinongy), commonly called muskie, are some species of fish that are raised in hatcheries and released for sport fishing. Many species that are used for stocking have low reproductive rates and slow growth rates. They are easily overfished if their populations are not supplemented through stocking.  Stocking lakes and streams can create new recreational fishing opportunities, support existing native populations of fish, and restore threatened or endangered populations. Lakes are often stocked right before the fishing season opens, or when a park is holding a regional celebration. If people have a good chance to catch a big, desirable fish, they are more likely to buy a fishing license. More fishing licenses sold means more revenue to use to protect and maintain natural resources.

Despite the benefits of fish stocking, not everyone feels that stocking lakes and streams with fish is a good idea. One large waterway conservation group, the Pacific Rivers Council (PRC), believes that using fish stocking as a management technique diverts money and other resources that could be better used in other conservation and protection efforts. The PRC has also found that a decline of native golden trout in California is linked to fish stocking. In total, 35 species of fish and amphibians have been affected by stocking practices in California alone.  Genetic hybridization between introduced and natural fish species can occur, which lowers the fitness of the natural populations. Adding fish to a lake or stream can also introduce disease, to which hybrid fish are more susceptible. A scientific study of Virginia streams found that the infectious pancreatic necrosis virus was found only in brook trout populations that had a history of fish stocking. In Wisconsin, seven species of fishes were found to have lymphocytis due to the stocking of walleye.

Fish stocking can also change the balance of an ecosystem. Fish that are stocked are often apex predators. Native fish species may become prey of the introduced fish, and existing populations will also have to compete for food and habitat. Many fish species prefer to have cover, such as undercut banks, abundant vegetation, or large rocks to hide beneath, but cover is limited in many aquatic ecosystems. Stocked rainbow trout have outcompeted many of the native brook trout populations in the southeastern United States. Even bird populations that feed on fish can be affected. Cormorants and other predator bird species prey heavily on trout when they are first stocked in Washington lakes. Trout that have been raised in hatcheries tend to stay near the surface of the water for the first few weeks until they start cuing into the natural food sources closer to the bottom of the lakes. How the sudden, short-term abundance of food for these bird populations affects the entire food web is unknown.

Despite all of these concerns, fish stocking happens regularly and often multiple times in a lake or stream during one season. In Virginia, researchers have found that despite regular stocking of rainbow trout, 80 percent of fish in streams are still native brook trout.  Minnesota’s Department of Natural Resources (DNR) determined that stocked muskie will coexist with natural fish species because the DNR uses biologically-based guidelines in choosing which lakes to stock and do not stock high densities of the predator fish. Some Minnesota residents, however, feel that the increased boat traffic that fish stocking causes also increases the risk of introducing invasive species such as Eurasian milfoil, an aquatic plant that is difficult to control. Throughout history of humankind, there have been many examples of introduced species that have caused havoc on ecosystems. Is fish stocking a similar story, or a sound management technique? 


1. What are the benefits of fish stocking?

2. What are the disadvantages of fish stocking?

3. In your opinion, is fish stocking ever a good idea, or should it be completely banned? Explain your answer.

More to Explore
Texas Parks and Wildlife Department Winter Trout Stocking Program Angling Tips
Endangered Fishes Hatchery


  1. Dane Heinecke says

    I really liked your post. I am a full on fisher so this blogs are really appealing to me and my friends. Cheers.

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