2021 Corps Aquatic Invasives Strike Force Blog

The Aquatic Invasives Strike Force (AISF), a Trail Conference Conservation Corps crew funded through the Lower Hudson PRISM, is committed to preventing the spread of aquatic invasive species through education and outreach to active users of New York’s waterways while supporting management efforts through early detection surveys and manual removal of target species. 

The AISF crew is managed, in part, by the LHPRISM Aquatic Invasive Species Program, hosted by Teatown Lake Reservation. 

Learn more about the program.

Table of Contents

April 2021

By Maya Thompson

With any crew, training and proper preparation are essential. It is no different for the Aquatic Invasives Strike Force (AISF). Before we can officially start for the season, there were a lot of things that needed to get done! As AISF crew leader, I have been a part of this pre-season process during the past month. It has been eye-opening to see just how much is involved, and I have loved being a part of it!

One of the main things that I have been preparing is training materials. Specifically, the AISF crew will be staffing three launches in our region for the 2021 season for the Lower Hudson Partnership for Regional Invasive Species Management’s Watercraft Inspection Steward Program. We will be providing guidance on how boaters can inspect their boats and protect our waters from aquatic invasive species at Sleightsburg Park, Riverfront Green Park, and Haverstraw Bay County Park in New York. As there is a lot of information that the crew needs to keep in mind, I tried to channel my experiences as a former Watercraft Steward with the Finger Lakes Institute when crafting the training presentation. I remembered back to the tips and tricks that were taught to me, as well as those that learned myself. Overall, although every day and inspection are different, I tried to provide insight as to what a typical day will be like. We will be reviewing this training in late May and will be at our launches for Memorial Day weekend!

We will begin surveying and monitoring aquatic invasive species in May as well, which is very exciting! Many water bodies have been surveyed in past years, but there are several new ones on the calendar that I am keen on surveying, especially as a new member of the team myself. I am eager to get out on the water and look forward to updating everyone on our surveys in the future!

May 2021

By Maya Thompson

Over the past month, the Aquatic Invasives Strike Force (AISF) crew has officially started their season and been busy on the water! We surveyed 6 waterbodies, including Lake Dutchess, Palmer Lake, Seven Hills Lake, Lake Sagamore, Teatown Lake, and Walton Lake, totaling 364 acres! These surveys provide data on aquatic vegetation and invertebrates and are important for early detection and rapid response efforts throughout the Lower Hudson Valley. Between the 6 lakes surveyed, the crew detected 6 aquatic invasive species: Eurasian watermilfoil, curly-leaf pondweed, water chestnut, European waterclover, Chinese mystery snail, and banded mystery snail. Determining the presence of these species is critical in informing lake partners about what invasive species are within their waters, determining potential management methods, and assessing the efficacy of management efforts that may have been taken in previous seasons. For instance, Teatown Lake began a treatment to manage invasive species last season, so the crew’s data this season will help to determine the effectiveness of that treatment!

The AISF crew likewise provided education and outreach about aquatic invasive species as stewards at boat launches over Memorial Day weekend, participating in the Lower Hudson Partnership for Regional Invasive Species Management’s Watercraft Inspection Steward Program. Although the holiday weekend was cold and rainy, some dedicated boaters still went out on the water and each of the crew members successfully guided their first watercraft inspections of the season. Fortunately, out of those inspections, we found no invasive plants or animals! However, we did find invasive plants in and around some of the launches, including curly-leaf pondweed and water chestnut, so we will definitely keep our eyes peeled and encourage boaters to follow aquatic invasive species spread prevention techniques to stop their spread! The AISF crew will be at launches at Sleightsburgh Park, Haverstraw Bay County Park, and Peekskill’s Waterfront Green Park throughout the rest of the season; if you see us please come and say hello!

June 2021

By Maya Thompson

The Aquatic Invasives Strike Force crew has been hard at work across the Lower Hudson Valley during the month of June! The crew has surveyed thirteen lakes since the month started, spanning 778 acres. From these surveys, we recorded 400+ observations of the presence, absence, and density of aquatic plants and invertebrates. Notable invasive species found include curly-leaf pondweed, water chestnut, Eurasian watermilfoil, fanwort, banded mystery snail, and Chinese mystery snail. We also expanded our efforts to include several rivers this year, including the Harlem River and Mianus River Gorge! Likewise, we visited The Great Swamp of the Hudson Valley to perform a removal of curly-leaf pondweed. However, when we arrived at the site, there was actually significantly less of the species than we anticipated! Instead, we found many patches of native pondweeds! So, although the day did not exactly go as planned, it was nice for the crew to see something opposite of what we normally see: fewer aquatic invasives and more native species!

Looking forward, the month of July is going to be jam-packed with water chestnut removals! Water chestnut is arguably one of the most recognizable aquatic invasive species in this region, with its triangular, serrate, floating leaves arranged in rosettes with 4-horned sharp-barbed nutlets. These nutlets are the reason the species is so successful, as they drop in August and can remain viable in the sediment for as long as 12 years. Although water chestnut is listed as a Tier 3 or established, species, young individual populations may have the potential for eradication or suppression, which is where the Aquatic Invasives Strike Force crew comes into play. We will be performing water chestnut removals in nine locations during the next month, including Rockland Lake, Putnam County Veteran’s Memorial Park, Canopus Lake, Constitution Marsh, Blue Mountain Reservation, and Chodikee Lake.

July 2021

By Maya Thompson

For the Aquatic Invasives Strike Force (AISF) crew, the month of July has been filled to the brim with water chestnut removals! Water chestnut is a common species in the Lower Hudson Valley, introduced to the United States as an ornamental plant in the mid-1800s. It is recognized by its triangular, serrate, floating leaves arranged in rosettes with 4-horned sharp-barbed nutlets. These nutlets generally drop by August, remaining viable in the sediment for up to 12 years. Although a Tier 3, established species in the region, young individual populations may have the potential for eradication or suppression, which is the reason that the AISF crew has focused on removing water chestnut during the past month! Over the course of July, the AISF crew has removed just over 105,000 plants from 11 sites! In total, these plants weighed over 14,000 pounds. With the help of our partners and 40 volunteers, we put in 326 hours of effort. We would like to thank everyone that was involved with this undertaking, including Audubon NY at Constitution Marsh, Westchester Parks Foundation, Three Arrows Cooperative Society, and the NYS DEC at Norrie Point Environmental Center!

The AIS Program has also been heavily involved with multiple stakeholders from Lake Sebago in Harriman State Park to devise a strategic plan for managing aquatic invasive species through early detection and prevention. Earlier this month, AISF Crew Leader Maya Thompson and AIS Program Coordinator Lindsay Yoder led an aquatic survey training session for the three group camps on Lake Sebago: Adirondack Mountain Club (ADK), Appalachian Mountain Club (AMC), and the American Canoe Association (ACA). The Lake Sebago ACA camp also spearheaded a pilot Watercraft Inspection Steward Program for a single Saturday at the public launch, where nearly 100 boats were inspected, providing significant support for the creation of a full-season program.

Looking forward, the AISF crew is excited to get back into surveying water bodies around the region, looking to identify both native and invasive plants. We are surveying many new lakes, including Roaring Brook Lake, Lake Awosting, Queensboro Lake, Silver Lake, Sylvan Lake, and more, as well as returning to some lakes that we already surveyed earlier this season!

August 2021

By Maya Thompson

The Aquatic Invasives Strike Force (AISF) crew returned back to their usual process in August upon finishing up a few water chestnut removals during the first week, totaling 19,150 plants and weighing 4,814 pounds. We surveyed 8 sites, totaling 392 acres, throughout the next few weeks, identifying both native and invasive plants. Many of these sites were in Harriman State Park close to where many of the Conservation Corps members live and work, so it was awesome to explore the lakes in our own backyard!

In addition to surveys, the AISF crew was involved in several different projects throughout the past month. First, we teamed up with Nicole White, the Croton Hydrilla Control Project Manager with the NYS Department of Environmental Conservation, to assist with the ongoing Croton River Hydrilla Control Project. This included a fun snorkel through a section of the Croton River where we searched for hydrilla, an aquatic invasive species, to help assess the efficacy and impacts of the treatment that the NYS Department of Environmental Conservation and partners have taken during the past five years. Second, the crew also assisted with a genetic study of Eurasian watermilfoil out of the University of Montana. We collected, processed, and shipped over 140 samples from 7 sites that researchers will extract DNA from to confirm whether the plants are truly Eurasian watermilfoil or if plants have begun hybridizing in our region. This work will give hopefully give us a better understanding of the distribution of hybrid milfoils and the severity of impact on native ecosystems. Lastly, we switched out our sandals for hiking boots and assisted the Terrestrial Invasives Strike Force crew at Three Arrows Cooperative Society, manually removing the Japanese spirea!

Next month, we will continue to monitor water bodies throughout the Lower Hudson Valley. We will re-visit several that we already monitored at the beginning of the season, and it will be interesting to see any changes between visits. We will also dedicate more hours to staffing boat launches because even as the weather begins to cool down throughout September, boaters are still out and about!

September 2021

By Maya Thompson

The Aquatic Invasives Strike Force (AISF) crew recently swapped out our paddles for pencils and switched gears towards data entry and reporting, but not before closing out the monitoring season with 10 more surveys during September! During these surveys, we monitored over 600 acres and found six invasive plants and animals. Several of these lakes were already surveyed earlier in the summer, which we do to capture species with varying phenologies across the entire growing season. One site, however, Sylvan Lake, was new for the crew, and our diligent monitoring skills, unfortunately, resulted in the first recorded presence of invasive zebra mussels (Dreissena polymorpha) in the lake. While seemingly common in the Lower Hudson region due to their Hudson River establishment, zebra mussels are still relatively uncommon in our freshwater lakes, making this observation crucial for our understanding of the species distribution. Our participation in the Watercraft Inspection Steward Program also came to an end over Labor Day weekend, where they inspected 109 boats and interacted with 186 people about important AIS spread prevention measures.

Several members of the crew also had the opportunity to participate in the NYS DEC’s response to a recent report of Northern snakehead (Channa argus) at the Basha Kill Wildlife Refuge in Sullivan County. Aquatic Invasive Species Program Coordinator Lindsay Yoder and crew members Claire McMahon, Caleigh Millette, and Sudha Petluri joined forces with the DEC and the U.S. Fish and Wildlife Service to collect water samples along the Basha Kill that were then filtered and sent to a lab for environmental DNA (eDNA) testing. eDNA is an increasingly popular tool being used in AIS management, as it takes less time and equipment in the field than manual sampling methods and can help identify the presence of inconspicuous invaders or species at low abundances.

October 2021

By Maya Thompson

Since wrapping up our aquatic surveys last month, October has almost solely been focused on reporting for the Aquatic Invasives Strike Force crew. This was the first time during the season that we got a look as to how all the data that we recorded throughout our surveys and invasive removals gets seen and utilized by stakeholders! Although it would be a lot to review everything that goes into these reports, we essentially developed two separate documents for each waterbody: one that reports on our aquatic vegetation survey data and one that reports on the data collected from any management performed, typically from water chestnut removals. These reports were designed to educate stakeholders about their waterbody and allow them to make appropriate management decisions.

Along with this office work, we also participated in one last field day, where we sampled for bloody red shrimp. Bloody red shrimp are an invasive invertebrate threatening the Hudson River. They are a threat due to their food preferences, as they feed on native zooplankton, potentially impacting aquatic food webs as zooplankton are an important food source for native fishes. In terms of the sampling that we performed for the species, we set light traps in the water at twilight at three different sites along the Hudson River. Bloody red shrimp are diurnal migrators, meaning that they move up in the water column around twilight, so we set the traps at this time in an effort to catch them while they are out in the water column as opposed to the rocky spots that they hide in during the day. These light traps emit a specific frequency of light that they head towards and eventually get funneled into a trap that they cannot escape from. We left the traps out overnight and retrieved them in the morning. Luckily, we did not find any bloody red shrimp at any of the locations we sampled!

To wrap up the season, it would be remiss if we did not celebrate our accomplishments! From mid-May to the end of June and the beginning of August to the end of September, we surveyed 40 waterbodies, totaling 2,385 acres. Through these surveys, we were able to submit 1,754 observations to iMapInvasives. When we were not performing surveys, we were manually removing water chestnut during the month of July, where we removed almost 121,000 rosettes and over 19,000 pounds! In closing, we want to thank everyone that was involved and helped us with the season. A special thanks goes to everyone at the Lower Hudson Partnership for Regional Invasive Species Management (PRISM), the New York-New Jersey Trail Conference and Conservation Corps, and all the amazing volunteers that dedicated their time to help us!