Killer shrimp (Dikerogammarus villosus) primarily spread through human activities, which significantly accelerate their movement into new aquatic environments. While they can drift naturally over short distances, their long-range dispersal is overwhelmingly aided by people using waterways for various purposes.
Key Pathways of Killer Shrimp Dispersal
The invasive killer shrimp utilizes several main methods to spread, predominantly linked to human interaction with water bodies.
1. Recreational Boating
- Attachment to Vessels: Killer shrimp can easily attach to boat hulls, engines, trailers, and other submerged parts. They are small and hardy, capable of surviving out of water for a period, making transfer between water bodies highly probable when boats are moved.
- Bilge Water and Livewells: Water retained in bilges, livewells, or bait buckets can harbor these shrimp, transporting them to new locations even if the vessel itself is thoroughly cleaned.
2. Commercial Shipping
- Ballast Water: A major vector for aquatic invasive species, ballast water taken on in one port and discharged in another can carry thousands of killer shrimp larvae, juveniles, and even adults over vast distances.
- Hull Fouling: Similar to recreational boats, the exterior of large commercial vessels can provide surfaces for killer shrimp to cling to, facilitating their movement between different aquatic ecosystems.
3. Angling and Fishing Equipment
- Contaminated Gear: Fishing nets, lines, waders, boots, and other angling equipment that have been in infested waters can inadvertently transport killer shrimp. The shrimp can cling to wet gear or be present in residual water or mud.
- Bait Buckets: Leftover bait or water from bait buckets, if not properly disposed of, can introduce the species to new fishing spots.
4. Other Human-Aided Mechanisms
- Water Sports Equipment: Kayaks, paddleboards, canoes, and even wetsuits can act as carriers if not properly cleaned and dried after use.
- Aquatic Plant Trade: Accidental transfer via contaminated aquatic plants sold for ponds or aquariums is also a potential, though less common, pathway.
- Scientific and Research Equipment: Equipment used for sampling or monitoring in contaminated waters can also spread the species if not disinfected.
Understanding the Threat
Killer shrimp are highly aggressive, outcompeting and preying on native species, which can severely disrupt local ecosystems. Their rapid spread and adaptability make them a significant ecological concern. For more information on invasive species, visit a reputable source like the National Invasive Species Information Center.
Preventing the Spread
Mitigating the spread of killer shrimp largely depends on responsible practices by waterway users. The "Check, Clean, Dry" principle is crucial:
- Check: Carefully inspect all equipment, boats, and clothing for any visible organisms or plant material before leaving a water body.
- Clean: Thoroughly clean all equipment with hot water (above 45°C or 113°F) or a strong disinfectant. If hot water isn't available, scrub vigorously with tap water.
- Dry: Ensure all equipment is completely dry for at least 48 hours before using it in another water body. Some invasive species can survive for extended periods in damp conditions.
By adhering to these simple steps, individuals can play a vital role in protecting native aquatic biodiversity from this aggressive invasive species. For detailed prevention guidelines, consult environmental agencies such as the Environmental Protection Agency.
