Occurrence of zebra mussel (Dreissena polymorpha) veligers in residual water from Minnesota watercraft

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Aquatic Invasive Species (AIS): Zebra mussel (Dreissena polymorpha)
Project Location: Minnesota
Project Start Date: 06/2013
Expected Timeframe/Duration: 2015
Sponsoring Organization: Minnesota Department of Natural Resources-(Division of Ecological and Water Resources)
Web Links:
Primary Contact: Gary Montz, MN–DNR
Minnesota Department of Natural Resources

Secondary Contact:
Project Summary:

Recreational watercraft can move zebra mussel veligers to uninfested waters through transport of water in areas such as live wells and bilges.  However, it is still unclear what level of risk this water movement has for creating new infestations.  Some recent studies from western North America have suggested that potentially large numbers of veligers may be moved.  Differences in sizes of watercraft and use between Minnesota and western states raises questions on what densities of veligers are in typical boats in the state.  

Laws in Minnesota require draining all water (live wells, bait buckets, bilges) and drain plugs must be removed during transport.  After required draining, residual water is still in some areas of boats.  To examine the possible veliger transport, this residual water was collected from drained boats exiting heavily infested Minnesota lakes and examined for veligers.  Water was collected from bilges, live wells, outboard motors and other areas in 2013 – 2014.  In addition, veliger tows were collected from an infested lake biweekly from different water depths to examine depth distribution across the summer. Sampling in 2015 will continue with an additional focus on watercraft such as those with inboard engines and/or ballast tanks (wakeboard boats).

This sampling can provide a clearer picture of this pathway and risk than extrapolation of assumptions from other regions of North America.  These data can also help prioritize inspection and decontamination efforts aimed at preventing spread through this potential pathway.