Licenced signal crayfish introductions (white circles), unlicensed observations inside signal crayfish region (orange circles, and unlicensed observations outside signal crayfish region (red circles) in Finland. a) Before 1989, b) 1st crayfisheries strategy era (1989–2000), c) 2nd crayfisheries strategy era (2001–2013), d) After 3rd crayfisheries strategy 2014–2016). Marked areas represent regions designated for signal crayfish in national crayfisheries strategies.