Tenacious Trespasser #4: New Zealand Mudsnail

New Zealand Mudsnail

(Potamopyrgus antipodarum)

What is it?

The New Zealand mudsnail is a tiny aquatic snail that inhabits lakes, rivers, streams, reservoirs and estuaries.  In addition to mud, the snail can also be found lurking on rock or gravel surfaces, aquatic vegetation, or woody debris.  New Zealand mudsnail are highly adaptable to diverse climates and can tolerate a broad range of aquatic conditions such as temperature, salinity, turbidity, water velocity, and stream productivity.  In the United States, New Zealand mudsnail populations are comprised almost entirely of self-cloning parthenogenetic females (no need for fertilization here).  The brood size of an individual female ranges from 20-120 embryos, each of which may mature to produce an average of 230 offspring per year – these gals could show Dolly the sheep a thing or two!       

FACT:  A single female mudsnail can result in a colony of 40 million snails in one year. 

What does it look like?

You better get your glasses out because this miniscule menace is only about 4 – 6 mm (1/8 inch) in length as an adult.   The snails shell is light to dark brown, with five to six whorls or spirals.  The opening of the shell has a retractable cover called an operculum which allows the snail to seal itself inside when it feels threatened or is exposed to pollutants.  Some fish and birds feed on New Zealand mudsnail, but the rigid operculum and thick shell wall enable many snail to pass through the digestive system of predators unharmed.    

FACT:  New Zealand mudsnails consume but cannot be consumed.  They hold no nutritional value for native fish species.

Where is it from and where is it now?

As its common name implies, the mudsnail is native to New Zealand and its neighboring islands. 

The New Zealand mudsnail has been introduced to Australia, Europe, Asia, and North America.  In the United States, the New Zealand mudsnail was first discovered in the Snake River (Idaho) in 1987.  Since this time it has become established in ten western states, five Great Lakes states and two Canadian Provinces (British Columbia and Ontario).

Benson, A.J. 2011.  New Zealand mudsnail sightings distribution.
Retrieved 2/26/2013 from newzealandmudsnaildistribution.aspx.

FACT:   The mudsnail’s ability to completely seal its shell allows the snail to survive out of water for several weeks in cool, damp conditions.

How did it get here?

The New Zealand mudsnail was first introduced to the US through contaminated ship ballast water and/or the transport of live fish or eggs for the commercial aquaculture industry.  Once introduced to a region, snails may be spread locally on the fur or feathers of terrestrial wildlife and pets (that means you fluffy), or consumed and dispersed in the excrement of local fish species.  Long distance dispersal of New Zealand mudsnail has been attributed to ballast water discharge, the movement of commercial aquaculture products (i.e., fish, eggs, and ornamental plants), and the transport of contaminated recreational gear.  This sneaky snail has an uncanny knack for hitchhiking on wading gear, nets, boats, and trailers of fishermen, boaters, and other water users, allowing it to be unknowingly spread to new areas.          

FACT:  Mudsnails can crawl at a rate of up to 10 feet/hour – these gals can really get around!

What are its impacts?

The high reproductive potential of New Zealand mudsnail enables it to reach extraordinary densities in some locations.  Researchers at Montana State University have reported densities of up to 750,000 snails per square meter in Yellowstone National Park.  Large colonies of New Zealand mudsnails can comprise up to 95 percent of the total macroinvertebrate biomass, and consume up to half of the available food in a stream.  New Zealand mudsnail may outcompete or displace native snails, mussels, and aquatic insects which native fish species depend on for food.  This disruption to the food chain may ultimately result in reduced growth rates and lower populations of economically important fish species.

FACT:  In Australia, New Zealand mudsnails have emerged from domestic water taps - gross!   

What is being done about it?

Once this horrible hitchhiker invades an area, there is very little that can be done to control or eradicate them.  Researchers are investigating the potential use of a host specific trematode to control the snail, but it is unknown how this parasite might impact native snail populations. 

Because the spread of New Zealand mudsnail is strongly associated with human activities, public education and outreach is still the best method to prevent their introduction and spread to new areas.  Informational signs are posted at boat ramps where New Zealand mudsnails have been found to alert boaters of their presence and what special precautions should be taken to minimize the risk of spread.  Many states (including Oregon) have mandatory boat inspection stations at state lines, boat ramps, and rest areas, where boats and other watercrafts are thoroughly inspected for the presence of mudsnails or other aquatic nuisance species.  If any are found, the boat is decontaminated on site at no cost to the owner.

FACT:  The New Zealand mudsnail has no natural predators or parasites in the United States.  In its native habitat, 11 different species of parasitic trematode keep mudsnail populations to a manageable size. 

How can YOU prevent the spread of mudsnails?

The small size of New Zealand mudsnails make them very easy to overlook and accidentally transport to new locations.  To minimize the potential spread of this tiny terror, follow these simple steps.

·       CHECK all recreational gear and clothing that has come in contact with water for any visible signs of sand, mud, or plant fragments which may indicate a tiny hitchhiker.

·       CLEAN all gear before leaving a site by scrubbing with a brush and rinsing with water.

·       DRAIN: all of the water from your boat (including the bilge, live well, motor), trailer, tackle and gear before leaving the area.

·       DISINFECT your gear (especially waders and boots) before traveling to a different water body.  Freeze your gear for a minimum of 6 hours (< 26°F), soak gear in a hot water bath for 5 minutes (≥ 120°F) (not recommended for Gortex), or soak gear in undiluted Formula 409 for at least 10 minutes. (http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev3_015418.pdf). 

·       DRY your gear completely (at least 48 hours) after each use.

·       NEVER transport live fish or any other aquatic plant or animal from one water body to another – it is illegal!

What if I find New Zealand mudsnails?

If you find New Zealand mudsnails or any other “tenacious trespasser” contact the Aquatic Nuisance Species Task Force at 1-877-STOP-ANS.  If you spot a potential aquatic invader in Oregon, contact the Oregon Invasive Species Hotline at 1-866-UNVADER.  In Washington State you can report a potential sighting at 1-877-9-INFEST.

Submitted by Donna Allard

Shifting Gears, Moving On...

The time has come for me to shift gears into a slightly different occupation  I think working with technology is super because the complexity naturally satisfies human curiosity while at the same time enables us to be more lazy -- by accomplishing more things with less effort -- which is definitely on my spectrum of human nature.

Working as an IT-Specialist at Columbia Fisheries Office is not just about technology however, it's about people. Specifically, people who value learning and expertise, value preserving our ecosystem and are smashingly good at optimizing constraint satisfaction problems with many human stakeholders. And while working for the biggest organization in US, the US, has its perks it certainly requires a particular finesse to have all gears greased and protocols followed.

I have tremendous respect for the work performed at CRFPO and feel lucky being partially involved over the last few years. I wish good luck to finding a replacement IT and of course a bigger budget for the years to come.

Submitted by Val Pavlenko

Best of Luck to you!

Restoration and Human Safety… Fish Passage Projects with Multiple Benefits

Working on private lands habitat restoration projects is a blend of science and art.  Our big picture strategies are guided as much as possible by the best scientific information in large-scale habitat assessment and resource prioritization plans.  We try to focus on strategically addressing the habitat limitations (the ‘life-history bottlenecks’) for key species like salmon across a wide variety of different land ownerships – including private and municipally owned lands. 

In several of our watersheds we have detailed assessments of road crossings (usually culverts) that are blockages to fish movements in rivers and streams.  The culverts are usually far smaller than the stream’s width, resulting in excessive velocities and scour that creates a drop, or perch, at the downstream end. We use the detailed assessments to select barriers that are ‘high priorities’ to address.  This is based on the length and quality of upstream habitat as well as on the number of at-risk or focal fish species that use the stream. But knowing where to work is just the first step.



Perched culvert in Roy Creek before restoration.



The day to day efforts are all about building relationships and partnerships.  That’s where the art comes in.  Working with a diverse array of partners and their broad range of goals means we have to find a way to achieve benefits for everyone while still being true to the intent of our conservation funding.  When you add a sluggish economy and declining budgets to this mix, it really gets interesting.  The collaborative mode is rewarding in itself, but it is also necessary when everyone has fewer resources.   The success of this work is really visible in some of our current restoration projects on Oregon’s north coast.  In addition to selecting projects that are high priorities from a natural resource standpoint, we also look to support critical infrastructure upgrades and to improve public safety.  All of the projects are beneficial to the local economy in that there are lots of jobs and materials purchased.



Seaside Heights Elementary students visit the new culvert
to learn about coastal streams.



Seaside Heights Elementary—When the Seaside School District learned that the culvert under the only access road to Seaside Heights Elementary School was failing and that it would cost nearly a half a million dollars to fix it, they were concerned about the welfare of their 320 students and their families who travel over the culvert daily.  The school had also been designated as a Tsunami Safe Area for the community, making safe access even more critical.  The school didn’t have cash or resources to fix the culvert, but an expedient and creative partnership between Seaside School District, USFWS, Necanicum Watershed Council, City of Seaside, Oregon Department of Fish and Wildlife, NOAA-American Rivers, and Oregon Watershed Enhancement Board provided design, permitting, and funding to fix it. The culvert was not only a failure risk; it was a barrier blocking migrating fish from nearly a mile of spawning habitat.  Culvert failure would have dumped 10,000 cubic yards of earthen fill into the stream, damaging habitat quality in the creek and in the productive beaver marsh below – both important rearing habitats for juvenile fish.  Working together, our team of partners installed a 16’ wide by 150’ long culvert with a natural stream bottom to ensure that adult and juvenile fish could move upstream and downstream at all flows.  The school got state-of-the art infrastructure and the City of Seaside got a secure access to a Tsunami Safe Area for their residents.  The school continues to work closely with the watershed council to use the stream as an ‘outdoor’ classroom to engage their students.

Tillamook County—Another important partner has been Tillamook County.  We have culvert assessments and prioritizations that cover nearly the entire county.  This has allowed a broad team of partners to work together to strategically implement projects that open streams to enable fish to move into quality habitat.  Local organizations, like the Nestucca-Neskowin Watershed Council and the Tillamook Estuary Partnership, have been important leaders in gathering the data and coordinating partners.   The Tillamook County Public Works Department has been a great cooperator as well, realizing that much of the infrastructure is under their jurisdiction yet they have extremely spare budgets to address the pressing needs-- even in the case of culverts at risk of failing.  Our projects in Tillamook County have helped salmon, steelhead, trout, and lamprey access important upstream habitats.  At the same time, these projects have also helped improve the City of Tillamook’s drinking water diversion and have fixed a barrier culvert under a county road and Port of Tillamook Railroad crossing.  This coming summer we will fix at least three other important county road crossings, including one that is in imminent risk of failing, and will work on several private lands fish passage projects this summer; providing fish and stream benefits while ensuring safe access to farms and homes, and for logging and gravel trucks and other coastal dwellers to travel a safer road network. 

Achieving the Mission—In the end these projects meet many goals.  They improve fish access to miles of important habitat and improve stream dynamics by removing artificial constrictions to restore natural stream flows and reduce scour of stream habitat features such as spawning gravels.  The projects help repair failing infrastructure that poses human safety risks.  They can help provide secure drinking water resources.  They stretch limited local municipal budgets in tough economic times.  They create an efficient and seamless partnership between local, state, and federal agencies where everyone contributes an essential piece in a complex puzzle. 

Tillamook county Commissioner Mark Labhart
speaks at the Roy Creek Ribbon Cutting Celebration.

The value of this type of partnership was recognized by Senator Betsy Johnson at the ribbon cutting ceremony on the Roy Creek Fish Passage project in Tillamook County last November, “This is really a big deal.  This goes to show what we can accomplish when we work together.” Her thoughts were echoed by Lower Nehalem Watershed Council Chair George Hemmingway, who said, “This just shows what can be done when people at the local community level, stakeholders and leaders, are encouraged and aided by government agencies at all levels. Bottom up and grassroots thinking, aided by county, state and federal experts and funds. What an idea…very Oregonian.”

And, last but not least, they achieve the Fish and Wildlife Service mission, which is after all, working with others to conserve, protect and enhance fish, wildlife, and plants and their habitats for the continuing benefit of the American people.

Submitted by Amy Horstman, Fish and Wildlife Habitat Restoration Program