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DEC's Plans to Eradicate Northern Snakehead Fish

In August 2008, The New York State Department of Environmental Conservation (DEC) plans to treat Ridgebury Lake and Catlin Creek above Route 6 in Waywayanda with the aquatic pesticide CFT Legumine. The DEC action is designed to eradicate invasive northern snakehead fish, protect clean water, and restore a healthy and productive fishery and natural community.

Riparian landowners who were initially notified of the proposed action in early July 2008 were sent a July 29th letter (PDF, 24 Kb) with additional information including: summary of and responses to public comments (PDF, 43 Kb); CFT Legumine product label (PDF, 510 Kb) and the treatment plan (PDF, 16 Kb). A press release has been distributed statewide via the Albany press office.

One August 13, the Natural Resource Supervisor in Region 3 sent a follow-up letter (PDF, 22 Kb) to Riparian Landowners to detail DEC's actions to restore the impacted waters.

August 13th Follow-up Letter

Dear Riparian Property Owner and/or Wawayanda Resident:

We are writing to update you concerning the Department of Environmental Conservation's efforts regarding the restoration of Ridgebury Lake and Catlin Creek. On Tuesday, August 5th, 2008 the Department began the process of restoring Ridgebury Lake and Catlin Creek downstream to the Route 6 crossing by treating these waters with the fish toxicant CFT Legumine to eradicate Northern Snakehead (Channa argus). As you know, northern snakehead is a highly invasive non-native predator fish that has the potential to prey on and compete with fish native to New York. It had become established in the headwaters of Catlin Creek, including Ridgebury Lake. As many of you have witnessed first hand, this has been an enormous undertaking, one that has resulted in significant impacts including a temporary loss of the fish population and the temporary disruption of the peaceful atmosphere of the waterfront lands you cherish. The sacrifices you have made to allow us to take aggressive action to eradicate this invasive species and prevent it from spreading throughout the state are greatly appreciated.

The Department took the following actions to restore the impacted waters:

August 5, 2008

All of Ridgebury Lake and portions of Catlin Creek and adjacent ponds downstream to point behind the Wawayanda Town Hall and the Town's Highway Department were treated.

August 6, 2008

DEC staff resumed treatment of Catlin Creek downstream from the Highway Department, including wetlands adjacent to the creek down to and including Hyde Pond, as well as the remainder of Catlin Creek above the Route 6 crossing. Treatment of all waters with the aquatic pesticide CFT Legumine was completed by 5:00 PM on Wednesday, August 6th.

After the treatment of the headwaters of Catlin Creek was completed, DEC staff collected and removed all fish that were casualties of the treatment process. While we will not have final results for some time, below is a brief summary of what information was collected:

  • Northern Snakehead Fish: Over 220 Northern Snakehead were found throughout the treatment area, from Ridgebury Lake downstream to Hyde Pond. Most (over 200) were juvenile fish, clearly demonstrating that Northern Snakehead were successfully breeding and reproducing in Catlin Creek. A variety of adult fish were collected as well, the largest being a 31 inch long fish weighing over 11 pounds from Ridgebury Lake.
  • Other Fish: Approximately 8 tons of fish were removed during our post treatment collection process, the vast majority coming from Ridgebury Lake. By far the greatest percentage of fish, by weight were common carp. In addition, largemouth bass, crappie, shiners, bullhead and yellow perch were collected. All were transported to the nearby NYS Department of Transportation facility on Route 6 where they were composted.
  • Water Quality Sampling: During and after the treatment process the Department has been sampling the waters in the treatment area for the presence of Rotenone, the active ingredient in CFT Legumine. To be effective, CFT Legumine was applied at a rate of 4 parts per million (PPM). Water samples have been taken at several locations in the treatment area as follows:
Rotenone Concentration in Parts Per Million (PPM)
Location Date (2008)
August 6 August 7 August 8 August 11
Ridgebury Lake 0.400 0.250 0.125
Catlin Creek 2.500 0.115 0.065 0.015
Hyde Pond 5.500 0.280 0.050 0.020
Catlin Creek @ Rt 6 0.095 0.095


Rotenone is not toxic to fish at levels at or below 0.05 PPM. We anticipate Rotenone to breakdown to where its presence is below that level in Ridgebury Lake later this week. Once we confirm that level, we will undertake a test with a small number of live fish before reintroducing previously captured fish into Ridgebury Lake as described below.

Prior to our treatment the Department took important steps to restore a healthy and productive fishery. During the week of July 28th, the DEC staff erected a series of five holding tanks behind the Town Highway Department to serve as a temporary home for live fish collected from Ridgebury Lake. On Thursday, July 31st and Friday, August 1st, DEC staff collected approximately 1,400 fish, including bass, crappie, yellow perch, bullheads and shiners, to be held and used to restock Ridgebury Lake once the lake water is determined to be safe for fish. While being held, the Department is also testing some of these fish for disease to ensure the lake is restocked with disease free fish. Once safe, the reintroduction of these fish will help accelerate natural restoration processes. This fall the Department will host a meeting with riparian owners to provide information regarding additional restoration options, including restocking of hatchery-raised fish, with a goal of developing a restoration plan for Ridgebury Lake.

While fish restocking efforts may begin later this month, the following activities will continue to be prohibited in the affected waters until September 5, 2008 (as posted):

  • Swimming and bathing
  • Fishing and/or fish consumption
  • Livestock watering
  • Irrigation or spraying of agricultural crops
  • Use of treated surface water for human consumption
  • Use of treated surface water for domestic purposes

While many local residents had significant concerns with our approach, everyone remained courteous to DEC staff, and many allowed the Department to occupy their private lands during and after the treatment process despite their reservations. The Department is especially grateful for these accommodations. While the success of our efforts are not yet proven, the Department acted to address this significant challenge and threat to this area.

We will be posting additional information on DEC's website, including some pictures illustrating many of the steps in the process. On behalf of the Department I wish to thank you all for your tolerance, patience and understanding, and for the assistance provided to aid our efforts. We look forward to your continued involvement as we continue our restoration effort. If you have additional questions, please don't hesitate to contact me at the number above or Regional Fisheries Manager Michael Flaherty at 845-256-3066.

July 29th Letter to Riparian Landowners

Dear Riparian Property Owner:

On June 25, 2008 the New York State Department of Environmental Conservation (DEC, Department) sent all known riparian property owners along Ridgebury Lake and Catlin Creek downstream to the Route 6 crossing a letter explaining proposed action to eradicate the Northern Snakehead (Channa argus) from these waters. On July 8, 2008, a public meeting at the Town of Wawayanda Hall was also held to provide information regarding the proposed treatment of these waters with the fish toxicant Prenfish. Department staff provided information about the life history of this aggressive invasive species and the potential ramifications should this species continue to infest Ridgebury Lake and spread to waters downstream such as the Wallkill and Hudson Rivers.

At the conclusion of the Department presentations the meeting was opened for questions and comments. Additional written comments were accepted until July 16. The Department wishes to thank all who attended the information session, provided comments, questions and suggestions or who otherwise responded. The concerns regarding serious impacts from this invasive fish, and the concerns and questions regarding potential health, environmental and other impacts from the proposed response, including the use an aquatic pesticide that has rotenone as it's active ingredient, are understandable.

As a result of comments and suggestions made, some revisions in the Northern Snakehead eradication plan have been made to address the concerns expressed. While some comments opposed the treatment, others were in support. This Department understands the resistance to eliminating the fish population in Ridgebury Lake and Catlin Creek. However, the indigenous fishes inhabiting these waters plus the natural communities and waters of the Wallkill and Hudson are likely to be severely impacted by Northern Snakeheads if this population is left unchecked. The National Management Plan for the Northern Snakehead calls for eradication of Snakeheads if at all possible. After considering all available options, including no action and attempts to contain the invasive fish, DEC concluded that reclaiming the area of concern with a registered pesticide is the most assured and appropriate action that can be taken to halt the expansion of this invasive species and protect and restore this important resource. The impending damage to Ridgebury Lake and Catlin Creek, and potential for statewide impacts to aquatic resources are too great for any lesser action. DEC is making a commitment to follow the treatment with restocking and restoration. And DEC plans to use a different aquatic pesticide than originally proposed (see below) to eliminate some of the other impacts people were concerned with.

An outline of DEC's plan is attached, and includes the following changes and clarifications to the original proposal:

  • Lake Restoration - Concerns about how fish populations in the treated area will be restored are understandable. The DEC will selectively remove and hold some fish collected from Ridgebury Lake prior to treatment and return them shortly after treatment, when the water is safe. The reintroduction of these fish will help accelerate natural restoration processes . DEC will work with the community, providing the technical support needed to develop and monitor the restoration of this fishery, and will support additional future restocking as determined by a cooperative effort between the community and the Department .
  • Odor - Several comments were received regarding the odor associated with Prenfish. Department staff have researched the use of an alterative fish toxicant, CFT Legumine that has no to very little odor. This product also has far fewer undesirable inert ingredients while still being an effective eradication tool. Therefore Ridgebury Lake and Catlin Creek will be treated with CFT Legumine (product label enclosed). The active ingredient, Rotenone, is the same in Prenfish and CFT Legumine.
  • Fish carcass - DEC will make every effort to remove the dead fish after treatment. A cleanup crew with trucks and equipment will be on site at the beginning of the operation and will continue the collection effort throughout the week or longer if necessary. Northern Snakeheads will be collected for analysis and all other fish will be transported to the New York State Department of Transportation's Highland composting facility.
  • Well contamination - Several residents expressed concerns that drinking water wells adjacent to the treatment area could be negatively affected. DEC and Department of Health staff have reviewed available information on possible impacts to ground water from CFT Legumine. Based upon the information obtained there appears to be no cause for concern that any of the ingredients in CFT Legumine would threaten groundwater. Comprehensive results from a risk analysis study can be found at: Further discussion on this topic can also be found in the attached Response to Comments.

DEC anticipates that the treatment will occur between August 4 and August 15, 2008. Some preparatory work could start earlier. Prior notification of the exact dates of treatment will be provided by posting of shorelines.

The following activities will be prohibited in the affected waters during periods of treatment and for up to 30 days after, as will be posted:

  • Swimming and bathing
  • Fishing and/or fish consumption
  • Livestock watering
  • Irrigation or spraying of agricultural crops
  • Use of treated surface water for human consumption
  • Use of treated surface water for domestic purposes

Attached are responses to comments that were received during the public meeting on July 8 and subsequent comment period that ended on July 16, 2008. Also attached find an outline of the treatment plan and a label for CFT Legumine. This information, including any updates or corrections, will also be posted on DEC's website. If you have additional questions, please don't hesitate to contact me at the number above or Regional Fisheries Manager Michael Flaherty at 845-256-3066.

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