Eurasian Watermilfoil

Plant Management Strategy

To find out more about the overall strategy and goals of plant management on the lake, and background of how and why the plant community has changed recently, find our comprehensive guide by clicking the button below:

About Species

Eurasian watermilfoil came into Candlewood (likely from a boat trailer) in the 1970's. It found Candlewood to be a hospitable environment and in a short amount of time, spread to much of Candlewood's shallow waters along the shoreline. Not only did it create dense mats of aquatic vegetation, but it out-competed important native vegetation, thereby reducing the biodiversity in Candlewood Lake. We have been battling milfoil ever since. 

Traditionally, the primary control method on Candlewood has been biennial deep winter drawdowns of the lake. Unfortunately, the lack of consistent cold weather conditions reduced the impact of deep drawdowns in killing exposed milfoil. So In 2015 the CLA began a sterile grass carp stocking program to help control this invasive aquatic plant.

The CLA and research partner Western Connecticut State University embarked on a study to see if the milfoil weevil (a tiny native aquatic insect) could be used as an effective biological control method for Candlewood's milfoil.  The study occurred over the course of 5 years, eventually concluding that while the population of the weevils did increase with the program, they unfortunately did not increase to the point where they had a visual impact on the milfoil.

Candlewood Lake Authority's Sterile Triploid Grass Carp Program

In collaboration with the State of Connecticut Department of Energy & Environmental Protection (CT DEEP), in 2015 the CLA stocked sterile grass carp in Candlewood Lake to help combat Eurasian milfoil.  A seperate stocking of the carp in 2017 raised the total population in the lake to around 8,000.

By eating from the top of the milfoil downward, the carp can help decrease the amount of “topped out” milfoil reaching the surface, particularly in coves and shallow areas where the problem can get particularly bad.

We continue to evaluate the current state of invasive milfoil in the lake to discuss the correct number of fish to be kept in the lake with the CT DEEP, who authorizes the quantity to be stocked in the lake through a permit process. FirstLight monitors the state of invasive plants on Candlewood Lake annually, and we are able to use those results to inform the grass carp program.


Not all Carp are Grass Carp!