Freezing and salinity used to control invasive mudsnails in Capitol Lake

The invasive New Zealand mud snail was discovered by a birdwatcher/shell enthusiast  in Capitol Lake in October of 2009.  There has been an intensive effort to control the mudsnail since it’s discovery.   Mudsnails outcompete native gastropods by outfeeding them and they don’t serve as an alternative food source for fish.  They have been spreading west from the Great Lakes where it is believed they were introduced through the release of European ship’s ballast water.

Wendy Brown from the Invasive Species Council warned the audience that these mudsnails have also been spread by unsuspected restoration biologists by moving them from one stream restoration site to another.  She also told the story of one biologist who found over 120 mudsnails hidden in the mud on his boots. 

Two primary methods have been attempted in Capitol Lake to try to control the invasion – freezing and increased salinity levels.   The freezing was found to be very effective – killing 98 percent of the snails.  The saltwater flush from opening the tidegate in the lake caused increased salinities above 20 for 7 to 8 hours.  This was much less effective than the freezing – only 12 percent mortality.  

Next steps will be to continue to experiment with freezing conditions this winter, weather permitting, and to do some follow up small scale trials of salt concentrations.

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