If you walk around Watershed Park or Yarrow Creek, you may soon see signs about preventing the spread of New Zealand Mud Snails. New Zealand Mud Snails were identified at these locations by King County invertebrate monitoring studies. The City of Kirkland has been working to establish a plan to prevent their spread into other creek areas to preserve healthy habitat for native species.

You can help by paying attention to warning signs, keeping yourself, your kids, and your pets out of affected creek areas, and following proper disinfection protocols if you do enter these creek areas. Read on for more information about this invasive critter, and ways you can help tackle the spread of invasives in Kirkland.

What are invasive species, and why are they a problem?

Invasive species are plants, animals, or other organisms that are introduced to an area outside their native range, usually by humans, which negatively impact the environment, economy, or human health. They often cause problems by taking over and crowding out native species, reducing species diversity in an area and decreasing the health and resiliency of native ecosystems.

How do New Zealand mud snails impact the creeks?

New Zealand mud snails (Potamopyrgus antipodarum) are very small, and spread easily from place to place. They have no natural predators, parasites, or diseases to control their population size in North America. Once they are established in an aquatic ecosystem, they are impossible to remove without harming native species.

 

One of the main ways that the mud snails harm an ecosystem is by crowding out native freshwater invertebrate species, which are a key link in aquatic food chains. New Zealand mud snails reproduce quickly – they have reached densities of over 500,000 snails in a square meter! The more of them there are, the less habitat is available for native stream bugs.

Fish may eat the snails in small numbers, but even when they do, the snails are so small that they provide very little nutritional value – and they often pass through the digestive system of the fish without being digested, and go on living! This means that over time, an area infested with New Zealand mud snails will have less variety of food for fish and other animals, and a lower quality of food, reducing the health of the ecosystem overall.

What can you do?

Stay out of the water and muddy stream areas anywhere that the snails have been identified. If you, your kids, your dogs, or any equipment does enter the creek bed in these areas, please follow decontamination protocols to prevent spreading the snails to new areas:

• Clean
  • Clean mud off of you and your equipment while on site
  • AFTER you leave the site, rinse gear in clean water, away from any body of water
  • Do NOT wash rinse water down a storm drain, as these are connected to creeks and may introduce the snail to a new location
• Drain
  • Drain excess water out of anything that you are taking away from the creek while on site
• Dry
  • Thoroughly dry anything damp until items are completely dry – 48 hours in the sun or 2 hours in a clothes dryer
  • Gear must be completely dry for at least 24 hours before reusing
  • Alternatively, freeze any items that have come into contact with stream water overnight at 26°F (-3°C) or below

Entering creeks unnecessarily can cause other issues for fish and other wildlife, such as crushing eggs in the gravel, stirring up dirt that can smother eggs downstream, etc. Drinking stream water can also be a source of disease for pets. When in doubt, it’s best to stay out!

What is the City doing?

In places where the City storm system intersects with these creeks, maintenance crews occasionally perform routine maintenance to prevent flooding in surrounding neighborhoods. Since the discovery of the New Zealand mud snail populations in this creek, maintenance crews have created decontamination plans to ensure that any equipment used during this maintenance does not spread the snails to other Kirkland creeks.

 

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Managing invasive species requires awareness and stewardship from all of us, on an individual and government level. Together we can help contain the spread of this new invasive species in Kirkland, and continue working to fight the spread of other invasive species in our city.

If you are fired up about stopping the spread of invasive species and want to be part of the solution, you can learn more about common weeds in King County and work to eradicate them on your property. Another great way to get involved is to participate in a restoration event with the Green Kirkland Partnership, which helps remove invasive weeds and restore native plants in our parks.