Fence Rock Lake in 2019

Fence Rock Lake, Guilford - 2019

2019 CAES IAPP survey map of Fence Rock Lake, Guilford

2019 Aquatic Plant Survey of Fence Rock Lake

Transect Data | Water Data

From 2009 to 2016, CAES IAPP surveyed Fence Rock Lake in Guilford, CT to track the invasive plant Brazilian waterweed (Egeria densa). The plant was first detected in 2009 and continued to spread. In 2013, these patches coalesced across nearly the entire cove. The increase in the coverage found the plant growing in deeper water than all previous years. Brazilian waterweed was found on 60 percent of the transect points in 2013.

In 2014, the lake was treated with the herbicide Reward® using a bottom injection technique. In the summer of 2015 a small population of Brazilian waterweed remained, so the lake was retreated. Our 2016 survey and 2017 surveys found no Brazilian waterweed.

In 2019, CAES IAPP performed another survey of Fence Rock Lake. Brazilian waterweed was found in a small patch by the private beach. The majority of the shoreline was populated by 19 different native species, an increase from the fifteen found in 2017. The most common species was watershield (Brasenia schreberi) and small pondweed (Potamogeton pusillus) was found in deeper waters away from the shoreline. Low watermilfoil (Myriophyllum humile) and white water lily (Nymphaea odorata) were also commonly found. A small section of common reed (Phragmites australis) was found on the northwestern shoreline. This species is invasive, but is not listed as such in our survey because it is a wetland plant, not aquatic. Fence Rock Lake has a diverse abundance of native species, and despite two herbicide treatments, Brazilian waterweed has reestablished.

Species recorded in our 2019 survey of Fence Rock Lake
Scientific Names
*Invasive Species
Arrowhead Coontail Primrose-willow
Small pondweed Watershield
Brazilian waterweed* Humped bladderwort Quillwort Snailseed pondweed Waterwort
Cattail Low watermilfoil Ribbon-leaf pondweed Spikerush
White water lily
Common reed Pickerelweed Slender naiad Watermilfoil Yellow water lily

Other Fence Rock Lake Surveys: 20212017201620132012, 201120102009