Montana Unauthorized Fish Introductions

Abstract

Montana Fish, Wildlife and Parks has maintained an unauthorized fish introduction database for more than 15 years that documents unwanted fish introductions across the state that have persisted long enough to be detected. The database currently covers 49 species of fish in 536 introductions in 298 waterbodies. Unauthorized introductions cover every drainage in the state and have caused impacts on native and recreationally important fish species, increased management costs, decreased recreational opportunity, and spread disease. Types and spread of introductions are discussed. The motivations behind illegal introductions are examined and linked to possible means of prevention and control.