Invasive exotic species such as American crayfish do not occur naturally in the Netherlands. They have however, established themselves here and continue to spread further. This is often at the expense of native species. American crayfish cause several problems, including:
- Damage to aquatic plants
- High rates of plant consumption leading to cloudy water
- Damage to flood defenses and banks due to burrowing
- Increased amounts of dredged material due to burrowing
- Dredged material that is difficult to process because it contains lobsters that can be spread further