Invasive Species

An invasive species are plants, animals and micro-organisms introduced by human action outside of their natural past or present distribution whose introduction threatens the environment, economy or society, including human health (Government of Canada, 2004).

There is a growing list of invasive species infiltrating Bobs and Crow lakes, and pose the largest natural threat to the long term health of the lakes.   For an in-depth discussion of invasive species go to:

Aquatic Invasive Plants

Eurasian Milfoil prefers water 1-3 m deep. Tiny plant pieces can develop into new plants.

Invasive plants are by far the most distressing threat to cottage owners and guests.  They affect boating, swimming, fishing and other recreational activities.  Residents and guests are increasingly frustrated with the "weedy" water fronts.   Care should be taken when trying to cut or remove these plants as they can easily spread from cuttings that re-root elsewhere on your lake front.   Common species are Eurasian Milfoil, European water chestnut,  fanwort, hydrilla, and water hyacinth.


Dime-sized Zebra Mussels

Invasive invertebrates include mussels, crayfish, snails, clams and waterfleas.   They adversely impact our aquatic ecosystems by out-competing for food and habitat with native fish species, and destroying fish spawning habitats.

Until very recently, there were no confirmed sightings of zebra mussels in Crow and Bobs lakes.   Unfortunately their presence in both lakes has now been reported by several residents.   It is hoped that their spreading within the lake will be constrained by the high calcium content of the water, which inhibits the growth of the shells of zebra mussels.  

This websiste offers an informative summary and a Zebra Mussels primer on the topic.

Zebra Mussels 101 

Invasive Fish

Black Crappie populations are increasing in Bobs Lake.

Although Bobs and Crow lakes do not have any of the severe predator species such as Asian Carp and Round Goby, there has been an introduction of other native species from other lakes.   The most notable is the Black Crappie.

Black Crappie while a good eating fish preys on young walleye.  Walleye (or pickerel) is a very popular fish among avid sports fishing enthusiasts on Bobs and Crow lakes. Many local fishermen feel the Black Crappie has contributed to reduced walleye catches in recent years.

Invasive Plants

Parsnip sap can cause severe skin burns.

Invasive plants that crowd out native species are a major objective of educational programs, to teach residents that what appears to be an attractive flowering plant is not necessarily good for the natural environment of the lakes.   Some of the most common invasive species are shown below:

Wild Parsnip is a member of the carrot family, whose sap contains chemicals that cause human skin to react to sunlight, resulting in intense burns, rashes or blisters.  Protective clothing and care should be exercised when gathering this plant.

Hogweed sap can cause severe inflammation of the skin.

Giant Hogweed is also a member of the carrot family. 

The stems of the plant are covered with reddish-purple flecks and stiff hairs filled with sap.   

Severe burns can result from this sap getting on the skin which is then exposed to sunlight.   Symptoms occur within 48 hours and consist of painful blisters.   

Forest Pests

Tent caterpillars are the largest defoliator of hardwood trees in N. America.

The Tent Caterpillar is native to North America and is not an invasive species.  However residents of Bobs and Crow lakes experienced a severe outbreak of the caterpillars in 2018.   Periodic outbreaks occur every 10-12 years and typically last from 3 to 6 years in a particular area.

Reporting Sightings

Reporting new sightings on Bobs and Crow lakes of an infestation of an invasive species potentially can help with their control.   For extensive information on invasive species, go to