Fish stocking: states are releasing nonnative animals by the millions

State wildlife agencies still stock millions of nonnative fish into lakes and streams to support recreational fishing and the license revenue that funds conservation, while scientists say those introductions can harm native species and ecosystems.

State wildlife agencies continue to release large numbers of nonnative fish into lakes and streams. The practice dates back to the late 1800s, when hatcheries were used to replace declining native fisheries. Today stocking persists because it supports recreational fishing and generates revenue from licenses that helps fund agency work. Scientists and advocates say those introductions can harm native amphibians and fish, alter food webs, and dilute local genetic lineages. Key facts: - States still stock millions of nonnative fish into waterways for recreational fishing, and many agencies report the practice remains common. - Stocking supports angling participation and is tied to funding: on average, more than half of state wildlife agency revenue comes from hunting and fishing licenses and related federal funds. - Research and experts report that introduced fish can prey on native amphibians and insects, displace local fish, and cause hybridization that threatens native genetics. - Some states now use measures such as sterile fish or focus stocking on altered or man-made waters, and a few are pursuing new conservation funding approaches. Summary: Stocking nonnative fish helps sustain recreational fishing and the revenue streams that fund much state conservation work, but experts report ecological costs including harm to native species and changes to food webs. A number of states have adjusted stocking practices or are exploring alternative funding, but broader policy change and long-term outcomes are undetermined at this time.