Survey Reveals 200 Acres of Invasive Hydrilla in Lower Connecticut River


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According to a recent survey, more than 200 acres of the lower third of the Connecticut River is overgrown with hydrilla, an invasive aquatic plant that, according to the Connecticut Agricultural Experiment Station, is among the most difficult to control.

“The big news from our survey is that hydrilla has been found in the Connecticut River,” said Greg Bugbee, an associate agriculture scientist at the Experiment Station. “The coves – Hamburg Cove and Whalebone Cove — are the most heavily impacted, along with sections near the shoreline that are three feet or less deep.”


The hydrilla in the Connecticut River is a new genotype not found in Asia, Europe or in other invasive growths in North and South America. According to Bugbee, the hydrilla is a hardier variety, and the best solutions for mitigation are unclear.

The survey of the lower third of the Connecticut River — designated the Gateway Conservation Zone in 1973 — was funded by the Gateway Commission and the Eight Mile River Wild & Scenic Watershed, and completed by Bugbee in 2019. The area stretches from Haddam and East Haddam to the mouth of the river.

As of 2019, more than 60 percent of inland wetlands across Connecticut already contain at least one invasive aquatic plant, compared to just 5 and 10 percent of lakes and rivers in nearby states.

Hydrilla present in the river leaves inland waterways and wetlands — like the many rivers and lakes throughout the state — more vulnerable to growth of this new invasive species. 

As of 2019, more than 60 percent of inland wetlands across Connecticut already contain at least one invasive aquatic plant, compared to just 5 and 10 percent of lakes and rivers in nearby states.

“Connecticut has probably the worst overall invasive species issue of all northeastern states, but no budget to handle it,” Bugbee said. “Connecticut is behind the other states when it comes to prevention, like boat launch monitors. Boats just come and go without much inspecting. It’s a big issue.”

And as of yet there is almost no funding set aside to put such measures in place, Bugbee said.

In 2019, the legislature passed a bill that would require all Connecticut resident boat owners to purchase a $5 invasive species stamp and out-of-state boaters to purchase a $25 stamp in order to operate a boat beginning in 2020.

“Funds from the AIS Stamp program will be set aside from Connecticut boating registrations and out-of-state boaters for the purpose of restoration and rehabilitation of lakes, rivers, and ponds; eradication of aquatic invasive species; education and public outreach programs; and for grants to conduct research and education on lakes, rivers, and ponds,” said Kristina Rozek, communications director for the State Department of Energy and Environmental Protection.

Rozek said that the grant programs from the funds raised for this are expected to be set up later this year.

“Maybe by this time next year we will have funding, but right now we only operate off grants,” Bugbee said.

The next steps — when the funding for the Experiment Station is in place — would be to survey the remaining two-thirds of the Connecticut River and assist DEEP in determining a management strategy for hydrilla as well as the other invasive plants in the river.

Prevention on a local level

The best thing to do when it comes to hydrilla, Bugbee said, is to prevent it from getting into the water at all. In lakes, such as Coventry Lake, where hydrilla has already taken hold, the town and state are spending more than $100,000 each year to control the weed with herbicides.

The Cedar Lake Watershed Commission in Chester has taken that lesson to heart and has approached the Board of Selectman with a proposal to prevent boats requiring a trailer to use the boat launch. The proposed ordinance would mean that only boats carried in, and less likely to bring invasive species with them, would be permitted in Cedar Lake.

“The new invasive aquatic weed most often comes from boats and trailers,” said Tom Brelsford, the chair of the Cedar Lake Watershed Commission.

According to Bugbee, there is data showing that lakes that have a boat launch ramp are more likely to have an invasive species than those that do not. Many other states, including New York, have instituted boat cleaning stations at launches in an effort to prevent the spread of invasive species from one body of water to another.

“We originally discussed the option of closing the boat launch altogether, but because of federal funding, DEEP said that’s not allowed,” Brelsford said.

The boat launch in Chester was renovated by the Department of Energy and Environmental Protection in 2002 through a grant provided by US Fish & Wildlife Service Sport Fish Restoration Program, according to DEEP.

“The launch at Cedar Lake continues to be seasonally maintained by DEEP staff using the same funds,” Rozek said. “The conditions for using such funding for construction, renovation or maintenance require that the state ensure that the facility continues to serve the purpose of which it was constructed.”

In order to minimize the chance of invasive species spreading, Rozek explained that the department hires seasonal boating education assistants to visit each state boat launch and educate boaters about the proper way to inspect boats for aquatic plants before leaving a lake and how to prepare boats prior to launching in another.

“For lake associations, DEEP will also train local volunteers who are willing to take on a greater role at launches in a more full-time capacity,” Rozek said.

The next steps for Chester to pass such an ordinance would be to hold a public information session to discuss the issues and possibilities for dealing with the problem of invasive species in the lake, said First Selectman Lauren Gister at a Monday night special meeting. The ordinance language would also require a review by the town lawyer and finally a vote by residents of the town before going into effect.

“The use of the lake has changed. More people are swimming the length of the lake now and there are a lot of kayaks and canoes. I see less fishing boats each year, and last year I saw just 16 all season,” Brelsford said on Monday at the meeting. “We as stewards felt it was important to get the information out and let the people in the town make the decision as to what to do.”

Currently there are no herbicides or pesticides being used in Cedar Lake to control invasive species, and the Town of Chester as a whole has banned the use of glyphosate (Roundup).