Lake Mahopac Park District Lake Mahopac Park District Lake Mahopac Park District
About Us
What's New
How can you help
Newsletters & Lake Reports
Fish Survey 2020
Winter deIcers
Points of Interest
Historic Lake Mahopac
Environmental Information
Construction on the Lake
Site Search
Photo Gallery
Related Associations
Water Conditions - How's the Water

How’s the Water?
This will be the thirty years since the grass carp were first introduced (October 1994) to Lake Mahopac for controlling the Eurasian Milfoil population.  The life expectancy of the sterile carp is about 12 years.  We have continued to perform both the water quality monitoring and vegetation study for Lake Mahopac.  After the Mifoil was gone there were large amounts of filamentous algae growing in place of the Aquatic Plants because of the lack of completion with native plants.  Twenty Years later the Aquatic Plants began to return and filamentous algae was going away. 
In 2013 the Biomass found measurable amounts of Eurasian milfoil and other vascular aquatic plant but still under the DEC guidelines of 30%.  In 2016, the plant biomass was at its highest just months prior to the initial restocking of the 200 grass carp in October 2015.  The sampling from the Biomass was conducted on August 26, 2020, at the same sites of the previous years and shows a huge reduction in Aquatic Plant growth. 
Since the initial 200 carp reintroduction in 2015 an additional 2400 carp have been released in Lake Mahopac as of 2021.  
The grass carp have reduced the Eurasion Milfoil at the annual sampling sites.  There are other plants that are native (non-invasive) to Lake Mahopac and should not been considered a threat to the lake’s ecosystem.  Aquatic vegetation is a source of (1) food for fish and small insects, (2) protection for breeding fish and (3) oxygen.  A moderate population of aquatic plants (20 to 30%) is essential for the long-term health of the lake.
In summary, the amount of grass carp has reduced the amount of Eurasion Milfoil from dominating in the lake and the water quality of Lake Mahopac is good.
More about Eurasion Milfoil: