Eurasian Watermilfoil
Eurasian watermilfoil grows in thick, dense mats that crowd out native species, reducing biodiversity, and deoxygenate water when decomposing, killing other aquatic species. It can also cause damage to boat motors, negatively impact fishing and swimming, and increase suitable mosquito habitat.
Description & Management
In 2019, Mississippi Valley Conservation Authority (MVCA) reported to Invasive Species Ontario that Mazinaw had “Eurasian Watermilfoil”(EWM). The Provincial government classified it as one of ten prohibited or restricted invasive species in Ontario; under the Invasive Species Act to help prevent, control and reduce their spread; and to protect Ontario’s environment, economy, human health and society from its harm. The government of Ontario and the Ontario Invasive Species Plant Council acknowledges that EWM invasive aquatic plants threaten our environment, economy and society.
As of 2024, we mapped approximately 15 Hectares of EWM (27 patches) interspersed around the lake, where depths are at 20 ft or less.
EWM can propagate very quickly from plant fragments which are created when someone in a boat, canoe etc. passes over the weed patch. The plant fragments become dislodged from the main plant and drifts down or is taken by waves / wind to new locations, then sink and colonize into new plants.
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The MPOA organized a 2 hour FAQ Information Session on August 15th, 2024 about Eurasian Watermilfoil. If you were not able to join us, see below for the written form of the FAQ as it relates to EWM.
Yellow Markers
What are the yellow markers on Mazinaw Lake?
The Mazinaw Blue Lakes Committee has installed yellow buoy markers to delineate colonies of Eurasian Milfoil, a very aggressive invasive species. The objective of the markers is to stop or reduce watercraft traffic in these
areas. Boat propellers, oars, and paddles cause the Milfoil to break off, re-root, and further the spread.
Please keep away from the marked areas. When boating, please stay on the deep water side of the markers.
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Mapping
Eurasian Watermilfoil
​During the summer and fall of 2023 the MPOA Board embarked on an orthomosaic surveying and mapping exercise to understand and quantify all locations of Eurasian Milfoil on the Lake.
At that time our findings concluded that there were approximately 15 hectares of Eurasian Milfoil interspersed throughout the Lake. This area represents 5% of the habitable area (shoreline of 20 feet or less).
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Unfortunately, as of Fall 2024, the quantity of colonies has increased by 17.4% (from 23 to 27 colonies) compared to last year’s survey. Based on the experiences of other Lakes, we can potentially expect 65% coverage of the habitable area (shoreline of 20 feet or less) in only 8 years.
