Invasive Species

What we are doing (as at December, 2020)

The Scugog Lake Stewards play a critical role in educating the general public about invasive species and what is necessary to avoid getting new species to add to the already troubling invasive aquatic plant, algae, fish, snail, mussels and more species communities already in our lake. (Over 150 different invasive species have been found in Lake Ontario alone, so there are many species that may still invade.)

We are constantly in touch with the Ontario Invading Species Awareness Program ( and have received 8 Clean, Drain, Dry signs to be placed by the Township at municipal boat launches around Lake Scugog over and above the large sign that we funded, designed, and had placed by the Township at the large Port Perry municipal launch sites.

We are advocating a boat wash station be installed at the Port Perry launch where most of the boats from other locations are brought in to our lake. In the new Township of Scugog Waterfront Revitalization Plan there is the idea to install washrooms at that boat launch which will mean that piping will be going in that will make installing a boat wash station not so costly.  However, constructing such a station will be complicated from many points of view and therefore, the Lake Stewards will work with the Township and Kawartha Conservation to find the  best engineering and technology for such an important installation.

Lastly, the Stewards are working with the general public, specific Citizen Scientists, researchers at Ontario University of Technology, and the Ontario Federation of Anglers and Hunters to check the lake and its shorelines for the first signs of new species sightings.

With many of these new invasive species proving to be so negative to our lake, impossible to remove once they have taken hold, or prohibitively expensive to control; we must all become aware of what we are actually seeing and reporting anything new or different to us or to the Invading species Awareness Program Edd Maps recording site at: 

What have we done (2019 report)

The Scugog Lake Stewards continue to be very concerned about changes that are occurring in Lake Scugog.  There are many things that we are working on to  Climate change is warming up the lake. New invasive species are dominating the aquatic life forms especially aquatic plants. There is more human development and therefore less natural surfaces and runoff patterns, as well as the changed consistency of that runoff especially higher chloride levels. Human development also changes the nature of the shoreline habitat in response to desire to ‘tidy’ and supposedly clean those shorelines.  Imported landscape practices from cities further reduce habitat.

Since 90% of all lake life begins, and is nurtured by shoreline habitats, these practices and occurrences play a big part in the health and diversity of our lake.

Over the years we have researched and tried a wide range of methods to get control of new invasive species with limited methods available. Anything tried must not harm other species in the lake, be against pesticide regulations and obviously be permitted by the Trent-Severn Waterway, the Ontario Ministry of Natural Resources and Fisheries and Oceans Canada. We started starting a CLEAN, DRAIN, DRY education campaign to educate boaters to clean their boats before and after enjoying Lake Scugog.  Several years ago, with funds from the Federation of Ontario Cottagers Association, we developed a large sign to be placed at the municipal boat launch in Port Perry.

Invasive species in Scugog began probably began shortly after settlement and the building of the dam at Lindsay. Very early on the newly flooded, and thus temporarily unhealthy lake area became home to malaria mosquitoes that arrived with with settlers. (See Construction of the Rideau Canal).  Later other species were either brought in or intentionally introduced.


History:  Changes in the fish population:

Types of bass were introduced in the late 19th century, walleye were stocked in the early in the 20th. Carp were probably released unintentionally from a fish farm either either on the Nonquon River or in Caesarea and now they are very prolific in the lake.  Black Crappie was probably introduced sometime about 20 years ago by someone looking to enjoy their favourite fish for the dinner table.

Mudcats, slang for catfish

With the arrival of so many predator fish, including the carp that took over its territory, the mighty mudcats of Lake Scugog have almost disappeared. Once caught by the thousands and enjoyed as very good eating; that sport fishery declined instead to welcome walleye and bass. Now walleye are in decline, mudcats seem to be increasing seen, especially the fingerlings.

History:  Changes in the aquatic plant community

Starry stonewort:  In 2015 the Scugog Lake Stewards were made aware of some very interesting and different overgrowth in some areas of the lake.  After having it checked out by Dr. Eric Sager of Trent University, we determined it was a new alga called starry stonewort. Since that time this alga has significantly replaced Eurasian watermilfoil and native plants in many areas of the lake. Rather than go into detail here we suggest that you check out our video on starry stonewort made by our research team, led by Dr. Andrea Kirkwood of U.O.I.T.  The Stewards, with U.O.I.T. will continue to research what effect this alga will have on our lake.

Port Perry Bay
Milfoil growth on Port Perry Bay

Eurasian watermilfoil:  Since the earliest recorded time in the local newspaper, Lake Scugog has always been a ‘weedy’ lake because of its muddy, rich bottom. But fish love aquatic plants. and fish and mammals have generally proliferated in abundance.  However, that weediness went into overdrive with the arrival of the invasive Eurasian watermilfoil, native of Eurasia in about the mid 1960’s.  It covered the lake for a while until eventually dying down to acceptable in about 1980. However, it then hybridized with the native watermilfoil which gave the new plants what is known as ‘hybrid vigour.’ The new plants were thicker stemmed and grew in denser stands. Their pink tips and flowers distinguish them. This milfoil pushed out almost all the native plants and made boating miserable.

The Lake Stewards used the only available method to try to find a solution:  to introduce greater numbers of the native milfoil weevil. Unfortunately, the rapidity of their reproduction was not as expected and the cost was excessive for a lake the size of Lake Scugog. Therefore the experiment was stopped although the large area where the weevils were originally introduced definitely showed great improvement.

But milfoil, although it is annoying for humans, is enjoyed by fish and other species in the lake.

Zebra mussels:  Zebra mussels arrived slowly to Lake Scugog, held back by the muddy bottom conditions of the lake since they are filter feeders. For some years they could be found on any hard surface such as pipe dock supports. However, with the introduction of the stronger stems of Eurasian watermilfoil and now the crunchy architecture of starry stonework, zebra mussels and now quagga mussels are proliferating. How they may together change water quality in the lake is being looked at in detail by our research team along with how it all affects our fishery including the walleye fishery.

There are many other invasive species in Lake Scugog; some pose a strong threat and some are just a problem in specific areas. For instance quiet bays may show areas of European frog-bit, other areas show large early spring patches of curlyleaf pondweed.  The native Canadian waterweed may sometimes be a problem to recreation although it is enjoyed by fish species.  Wetland areas are being taken over by phragmites Australis a tall, plume like grass which is turning wetlands into dry lands through their woody root systems.

The Stewards ask for your help in monitoring your area of the lake and reporting any new species to us at: