Using Triploid Grass Carp to Control Aquatic Vegetation

Invasive aquatic weeds can create major impacts on freshwater ecosystems. One of the primary reasons invasives are able to thrive, spread rapidly, and outcompete native species is that the environmental checks and predators that control these species in their natural settings are lacking in the ecosystems and habitat in which they become introduced.

The subsequent damages they cause occur on many ecological levels including competition for food or habitat (feeding, refuge, and/or spawning), direct predation and consumption of native species, introduction of disease or parasites, and other forms of disruption that lead to the replacement of the native species with the invasive species. As a result, invasives often cause serious harm to the environment, the economy, and even human health.

Some of the more commonly occurring non-native aquatic plant species that impact East Coast lakes, ponds, and reservoirs include curly-leaf pondweed, eurasian watermilfoil, hydrilla, and water chestnut.

The introduction of triploid grass carp to freshwater lakes and ponds can be an effective solution and natural alternative to managing and mitigating aquatic weed growth. When stocked at a proper rate, at correct sizes, targeting proper plant species, and the right time, triploid grass carp can reduce or eliminate the need for chemical treatment of the water to control aquatic vegetation.

Originally from Asia, grass carp have been imported to the United States since the 1960s to intentionally release into controlled freshwater environments for aquatic plant control. Grass carp, which rely almost entirely on aquatic plants for their diet, prefer to eat many of the non-native aquatic plant species that negatively impact freshwater environments, including the aforementioned pondweed species and watermilfoil.

Triploid Grass Carp in Woodridge Lake

Woodridge Lake is a beautiful 385-acre freshwater lake tucked away in the hills of Litchfield County, Connecticut. The lake, which is fed by the Marshepaug River, is a man-made resource, with a dam at one end that allows the level of the lake to be controlled.

Woodridge Lake Property Owners’ Association (WLPOA) closely monitors the lake, conducting water sample testing on a weekly basis. As with all waterbodies, the lake experiences aquatic weed growth, some years worse than others due to a variety of factors including climate change.

As a method to naturally mitigate aquatic weed growth, WLPOA plans to introduce triploid grass carp to the waterbody. A study by the Connecticut Agricultural Experiment Station states that grass carp is “the only biological control used successfully in Connecticut.”

Since the grass carp are an introduced species, only triploid grass carp, which are sterile, can be used. This eliminates the possibility that the stocked fish can reproduce and overpopulate the lake, or if any were to escape the lake they could not affect other waterbodies. As an additional measure of protection, to ensure that the carp remain in the lake, a screen, or emigration control device, is required. Princeton Hydro, in partnership with WLPOA, Rowledge Pond Aquaculture, and CTDEEP recently completed the installation of a carp screen.

The screen, which was custom designed by Princeton Hydro, is located in the outlet structure of the Woodridge Lake Dam, downstream of the spillway crest and within the concrete stilling basin of the spillway structure. Subsequently, the installation and operation of the carp screen will have no impact on spillway capacity or water surface elevations at the spillway crest. In addition, there will be no impact on the flow capacity or the water surface elevations of the Marshepuag River downstream of the dam outlet structure.

The emigration control device is a modular, vertical-bar screen composed of eight sections. A modular screen design was chosen to facilitate off-site fabrication and easier installation, as well as repair of an individual section, if necessary. Installed, all eight sections transect the entire 40-foot width of the spillway structure.

WOODRIDGE LAKE CARP EXCLUSION DEVICE DESIGN by Princeton Hydro

The carp screen was specifically designed to be easy to operate and maintain, minimizing clogging and facilitating easy cleaning from the downstream side of the screen during a range of flows. The operation and maintenance plan also consists of inspections every three months and precipitation-based inspections conducted by the WLPOA staff.

Overall, the use of grass carp will help Woodridge Lake manage aquatic weed growth in a natural way and maintain a healthy and vibrant lake environment for years to come.

To learn more about Rowledge Pond Aquaculture, the oldest private fish hatchery in Connecticut, go here: rowledgepond.com. For more information about Princeton Hydro’s lake management services, go here: bit.ly/pondlake.

PHOTOS: #BagThePhrag Update from Roebling Park

We’re gearing up for another invasive species treatment event at Roebling Park!

Located in Hamilton Township, New Jersey, Mercer County’s John A. Roebling Memorial Park offers residents in the surrounding area a freshwater marsh with river fishing, kayaking, hiking, and wildlife-watching. The park contains the northernmost freshwater tidal marsh on the Delaware River, Abbott Marshland. Since the mid-1990s, many public and private partnerships have developed to help support the preservation of this important and significant marsh.

Our Field Operations Team was recently at the project site assessing present invasive species and re-evaluating access points for our treatment equipment. Check out these photos from their visit!

 

For more information on this marsh restoration project at John A. Roebling Park, visit our original project blog:

Restoring the Northernmost Freshwater Tidal Marsh on the Delaware River

Deal Lake Commission Wins Award For “Lake Management Success”

NALMS President Dr. Frank Browne with Princeton Hydro Co-Founder Dr. Stephen Souza accepting the “Lake Management Success Stories” award on behalf of the Deal Lake Commission.

The Deal Lake Commission’s success in the management and restoration of Deal Lake garners a prestigious award from the North American Lake Management Society

 

The North American Lake Management Society (NALMS) awarded the Deal Lake Commission (DLC) with its “2018 Lake Management Success Stories” award. The award, which was presented at the NALMS 38th International Symposium, is given annually to recognize and honor an individual or group that has made significant lake/reservoir management accomplishments.

The DLC has overseen the management and restoration of Deal Lake and its watershed since 1974. Consisting of appointees from the seven municipalities abutting the lake, the DLC’s mission is to provide leadership, guidance and resources to preserve and restore Deal Lake and its tributaries as a healthy and stable ecosystem. A true challenge in an urban environment.

“It has been both a pleasure and an honor to work with the Deal Lake Commission for the past 35 years,” said Dr. Stephen Souza, Princeton Hydro Co-Founder. “They have shown great resolve to tackle some serious problems affecting the lake and its watershed, serving as a great example for other organizations involved in the restoration of urban lakes.”

Deal Lake is New Jersey’s largest coastal lake, encompassing 162 acres. The lake is surrounded by a 4,400-acre highly urbanized watershed, with the majority of development dating back to the 1960s-1980s. As a result, stormwater management, particularly with respect to water quality and volume management can be especially challenging. The DLC has embraced the numerous challenges, and has worked diligently over the years to correct these issues.

Restored shoreline at the Asbury Park Boat Launch in Deal LakeAt the forefront, the DLC has been managing the primary cause of the lake’s eutrophication: stormwater runoff from the surrounding watershed. In 2014, with funding provided through the NJDEP’s 319(h) program, the DLC implemented a number of demonstration projects, specifically the construction of three bioretention basins, the installation of a large manufactured treatment device, the vegetative stabilization of over 500 feet of heavily eroded sections of the shoreline, and the construction of a rain garden at the Deal Lake boat launch.

Collectively these projects were shown to eliminate localized flooding, decrease floatable loading, and reduce nutrient, sediment and pathogen inputs to the lake. These and other projects implemented by the DLC over the years show that despite Deal Lake being located in a highly urbanized watershed, it is possible to implement cost-effective green infrastructure and stormwater retrofit solutions.

Deal Lake recently won another very competitive 319 (h) program for $735,000 for MTDs, tree boxes, and Green infrastructure improvements to Deal Lake, Sunset Lake and Wesley Lake.

The NALMS award nomination application, which was submitted by Dr. Souza, listed a number of additional achievements of the DLC, including:

  • Educating the community, including school children, to increase awareness and appreciation for the natural environment of the lake;
  • Sponsoring and conducting public engaged spring and fall cleanups, which annually result in the removal of 1,000s of pounds of refuse and debris from the lake;
  • Helping homeowners and public groups recognize and mindfully solve problems related to water quality, siltation, and lake restoration;
  • Serving as the liaison between lakeside communities, County agencies, and the NJDEP;
  • Microbial source tracking investigations with Monmouth University and pathogen source identification work with Clean Ocean Action to decrease E. coli loading;
  • Carp removal, invasive species management, and goose control initiatives;
  • Working with State legislators to implement stricter stormwater controls to reduce pollutant loading, increase storm resiliency, and improve recreational fishing;
  • Participating in the NALMS Secchi Dip In; and
  • Proactively suggesting and supporting community-based, practical ideas to improve the overall environmental quality of the lake and its enjoyment by boaters, anglers, hikers, residents and visitors.

For more information on the Deal Lake Commission, visit DealLake.org.

The successful, long-term improvement of a lake or pond requires a proactive management approach that addresses the beyond simply reacting to weed and algae growth and other symptoms of eutrophication. Our staff can design and implement holistic, ecologically-sound solutions for the most difficult weed and algae challenges. Visit our website to learn more about Princeton Hydro’s lake management services: http://bit.ly/pondlake.