Photograph of a canoe with two people in it looking into a river with a large tree covered hill behind them.

Aquatic Invasive Species Region 3 Program

NYSDEC Region 3 is made up of the seven counties that make up the lower Hudson valley (Dutchess, Orange, Putnam, Rockland, Sullivan, Ulster, and Westchester).  The region boasts a diversity of aquatic resources and recreational opportunities centering on the Hudson River and its’ system of tributaries. The introduction and continued expansion of aquatic invasive species in this region imperils the native species and decreases the use of recreational areas.

Hudson River Water Chestnut Management

North (left) and south (right) Esopus vegetation survey. Two rake tosses took place at each of the points. The overall abundance on the rake was measured for each location. (0=Zero, 1=Trace, 2=Sparse, 3=Moderate, 4=Dense).

Satellite photo of north and south Esopus with points showing a vegetation survey and abundance found at each point.

The prohibited (6 NYCRR Part 575) aquatic invasive plant water chestnut (Trapa natans) was first introduced to New York State in the late 1800’s. It is now found throughout New York. Once water chestnut becomes established and expands it is challenging and expensive to remove. It alters native habitats, impacts fisheries, prohibits recreation, affects water use safety, emergency access locations, and local economies.

To our knowledge only manual and mechanical removal have been used for water chestnut management in the Hudson River and its tributaries. Both methods are not feasible for large-scale infestations. We propose to use chemical treatment which involves the foliar application of imazamox, an herbicide that has been successfully employed at other locations in New York State. Unlike most foliar applications which are conducted via backpack sprayers and spraying from boats we will be piloting the use of an unmanned aerial vehicle (UAV or drone) to apply the herbicide to increase efficacy and reduce cost. As with all water chestnut projects the goal is to reduce the population to a few plants/small patches that can be monitored, and hand pulled on a yearly basis. In addition, we are supporting and, in some cases, embarking on research regarding ecological impacts of water chestnut to help inform management decisions and predict their outcomes at the native animal and plant community levels. 

​NYSDEC Invasive Species Coordination Section endeavors to conserve aquatic habitats to create resilient systems for native biodiversity preservation and improvement recreational use. Management of water chestnut in the Hudson is proposed with the following justification. 

  • ​Improved access for boating and fishing recreation
  • ​Increase knowledge and experience in large scale treatment of water chestnut in a flowing tidal system.
  • ​Decrease invasive species pressure to allow for potential native species recovery. 

Restoring Native Submerged Aquatic Vegetation (SAV)

A focus of the Region 3 AIS Program is restoring native submerged aquatic vegetation (SAV) in areas where invasive species and their treatment have reduced native species populations.  Native aquatic species play a critical role in maintaining healthy aquatic ecosystems. They provide habitat for fish and other aquatic animals, serve as an important food source that supports the broader food web, provide oxygen to the water through photosynthesis, and help stabilize sediments with their roots which reduces water turbidity and can help improve overall water chemistry. 

Local genotypes of native species are favored for projects and may be collected prior to planned invasive species management to propagate and re-plant after invasive species removal. This approach helps ensure that restored populations maintain the local adaptations for the specific ecosystem. Water celery (Vallisneria americana) is being restored in the Croton River after the removal of invasive Hydrilla. The methods of propagation and planting of SAV will be expanded to additional sites in the Hudson River and tributaries. 

Looking ahead, Region 3 AIS program will start expanding restoration efforts to include additional native submerged plants, such as hornwort, Ceratophyllum demersum, and several species of native pondweeds. Stocks of these plants will be collected from relevant local environments and will be cultivated in a greenhouse environment. These efforts aim to strengthen native plant communities and promote long term ecological resilience in aquatic habitats previously impacted by invasive species.

Photograph of a person holding a burlap sack with young aquatic plants above a large tank of water in a greenhouse.

Technician Meghan Odell placing burlap bag of Vallisneria turions in soil into greenhouse tank to grow out prior to installation into the river.

Photograph of a green grassy plant underwater.

Vallisneria americana installed into the Croton River.

Project Plan and Reporting

Regional Reporting