Tag Archives: Northern Snakehead

Staff Manages Snakehead Threat At Huntley Meadows Park

Thirty-three Northern snakeheads were removed from the central wetland last fall.

Fifty Northern snakeheads were removed from the central wetland last summer.

One of the wildlife critters we’ll be keeping an eye on following the wetlands reconstruction at Huntley Meadows Park is the Northern snakehead. The exotic, predatory fish has been in the Dogue Creek portion of the Potomac River since at least 2004. They are well established in the Potomac River and have spread to other Chesapeake Bay tributaries. They were first seen in the Huntley Meadows central wetland in 2009.

Now, five years after the first sighting in the park and following the reconstruction that adds water depth to the central wetlands, there are new questions about the impact the snakehead will have at Huntley Meadows.

We sat down with the experts to get a better feel for the issue. Here are some questions and answers about snakeheads from that conversation with Huntley Meadows Park Manager Kevin Munroe, Huntley Meadows Resource Manager Dave Lawlor, and former Park Authority Resource Management and Protection Branch Manager Charles Smith:

Which species are most at risk from the introduction of snakeheads to the central wetland?

Smith: From our discussions about wetland management, the biggest concerns are the amphibians, particularly the frogs. Huntley Meadows has one of the only, and certainly the largest, breeding populations of southern leopard frogs in the region. There is concern that snakeheads could greatly reduce this population.

Lawlor: The native fish species will likely see the biggest impact from snakeheads.  However, after an electroshocking project last summer, the fish biomass and species abundance was very high and impressed everyone present, including the experts.  We do not know what kind of impact they are having on our amphibian populations.  The most significant impact would be the southern leopard frogs.  However, given the wetland project’s deep pool habitat created for fish and their predators (kingfishers, otters, bald eagle, grebes, etc.), all fish, including snakeheads, will probably experience more predation. This is a good thing, as it creates a more complete food web, and it may mean snakeheads experience more control from otters and eagles.

Staff use electro-fishing equipment to shock and count fish. Snakeheads are removed.

Staff use electro-fishing equipment to shock and count fish. Snakeheads are removed.

Is there any evidence that snakeheads are negatively impacting any species in the park?

Smith: There is no evidence yet.

At what age do snakeheads start having babies?

Lawlor: I believe they are sexually mature when they reach about 12 to 16 inches long.  We caught two here a couple of years ago, both around two to three pounds (17 to 20 inches), and they were both full of eggs.

Small schools of snakehead fry have been seen near the park.  Where would the adult female live?

Smith: In the same general environment – shallow water, often in vegetated areas.

Lawlor:  Females snakeheads of breeding age are living in the wetland complexes and likely in the central wetland along with many siblings and offspring.  Staff conducted an electroshock cull last summer while the wetland was drawn down for construction. Fifty snakeheads were removed from the wetland, including some large three to five-pound specimens.  Unfortunately, it appears snakeheads are here permanently, and we will have to continue to manage their populations.

Which animals eat snakeheads? Is it enough to control the snakehead population?

Smith: Wading birds, osprey, eagles, otter, snakes, and snapping turtles can all eat snakeheads depending on their size. It apparently is not enough to prevent snakeheads from breeding, but no one knows if there are enough predators to keep the snakeheads in check.

Lawlor: I would just add other fish, assuming other fish are able to survive in the wetland with them.  With the deeper pool habitat being created with the wetland project, other fish (crappie, perch, sunfish etc.) should have a chance to flourish in the wetland, too, and all of these fish eat other fish.

What should a person do if they spot a snakehead in Huntley Meadows? Is it ok to net and kill snakeheads on the boardwalk?

Lawlor: We ask people to notify us if they see a snakehead in the park.  We would prefer not to have the public randomly killing fish.  Not everyone knows how to ID a snakehead.

Is there a program in place to monitor snakeheads in the central wetland? 

Lawlor: I wouldn’t say we have a plan to monitor them, but they will be managed by removal whenever possible.  We are considering doing some removal this summer.

Are there any regularly scheduled culling dates?

Smith: Part of the design of the wetland restoration is to create deeper pools that can provide habitat for fish and other species during drought periods. During extremely low water, snakeheads should be confined to these pools. Park and county staff could then enter the pools with electrofishing equipment and remove all of the snakeheads in the pools while leaving the native species. This should provide the opportunity to greatly reduce the snakehead population every several years if not control them outright.

Lawlor:  We don’t have regularly scheduled culls, but we did a cull last summer and will continue to conduct culling operations when low water levels make it possible.

Is there a point at which we say, well, snakeheads are here, they may be non-native but they’re now a part of our local ecosystem?

Munroe:  We don’t know enough yet about the impact snakeheads have on our native ecosystems. They may turn out to be less of an issue than we originally thought, or they may be much worse. As we learn more, we can get a better handle on what our long-term approach and attitude should be.

Lawlor: I think that it is safe to say they are here to stay, after seeing the numbers of fish we removed from the wetland this past summer.  We have to accept that they are here, but we will do our best to manage the populations and keep their influence on our delicate ecosystem as small as possible.

What will deeper water in the wetland, one result of the reconstruction project, mean for the proliferation of snakeheads?

Smith: They can go where the water is, so snakeheads would follow the expanding pool during deeper water periods.

Lawlor: Also they would be able to survive the most severe droughts that would normally kill off their population. So the deeper water will ultimately benefit their populations in the wetland. But as Charles mentioned, this will be an opportunity for staff to manage their number by catching or shocking them in the deep water pools as we did in summer of 2013.

How big can a snakehead grow in the central wetland?

Lawlor: This is still unknown in the wetland system.  A record snakehead was caught in the Potomac River in 2013, around 17 to 18 pounds.  I am not sure they will be able to get that big in the wetlands because they will not have nearly as much forage – if they stick to fish.  So far the biggest snakehead caught in the central wetland was about five pounds.

Bowfin, lamprey and American eel look a little like snakeheads. Are those fish seen in Huntley Meadows?

Munroe: American eels yes, but not the other two species. However, eel have uniformly brown backs and sides, while snakeheads are patterned with black blotches on a pale background, much like a python, hence the name.

Former Huntley Meadows Park staff member Danielle McCallum holds a 17” Northern snakehead caught while electro-fishing Dogue Creek in 2008.  This was the first snakehead caught in the park.

Former Huntley Meadows Park staff member Danielle McCallum holds a 17” Northern snakehead caught while electro-fishing Dogue Creek in 2008. This was the first snakehead caught in the park.

Lawlor:  American eels are common in the Dogue Creek and Barnyard Run watersheds.  The least brook lamprey is also found in the Dogue Creek Watershed, although none have been found in the wetland yet.  Least brook lampreys are typically less than six inches in length.  As Kevin mentioned, eels and lampreys are generally a solid brown or tan and do not have any patterns on their flanks making them easily distinguishable from snakehead fish.  I am not aware of any positive ID of a bowfin in Fairfax County, but they are found in some Virginia rivers.

Can people fish for snakeheads in Huntley Meadows?

Munroe: No. Fishing is not allowed at Huntley Meadows Park.

Is it safe to say that snakeheads are breeding in the central wetland?

Lawlor: Yes!  We will continue to manage their populations the best we can to reduce their influence on the wetlands ecosystem.

Prepared by Matthew Kaiser, deputy public information officer; and Dave Ochs, stewardship communications manager.

Advancing Northern Snakeheads Thwarted at Huntley Meadows Park

Resource Manager Dave Lawlor shares the history of Northern Snakeheads in Dogue Creek and recounts a close call with this invasive fish at Huntley Meadows.

Former Huntley Meadows Park staff member Danielle McCallum holds a 17” Northern Snakehead caught while electro-fishing Dogue Creek in 2008. This was the first snakehead caught in the park.

Huntley Meadows Park, a 1,500-acre complex of freshwater marshlands located in Alexandria, Va., has long been a destination for birders, wildlife photographers, and students. No matter the season, people flock to the boardwalk trail to observe migrating birds, soaring raptors, moss-covered turtles, beavers, delicate dragonflies, and many more species in the park’s 50-acre central wetland, the largest in the region. Freshwater wetlands are considered rare habitat in the Washington, D.C. region and harbor the greatest biodiversity of any habitat type in temperate climates. However, in recent years Huntley’s central wetland has come under threat from an invasive fish species, the Northern Snakehead. If allowed to breed within the park, with their voracious appetites snakeheads have the potential to wreak havoc on the park’s large populations of amphibians, reptiles, birds, and mammals.

Listed by the state Board of Game and Inland Fisheries as a predatory and undesirable exotic species, snakeheads have been slowly migrating from the Potomac River up Dogue Creek toward the central wetland since 2004. Nine snakeheads were caught in the tidal section of the creek that year, and a year later two fishermen caught more than 80 young fish only a mile and half downstream from the park. Once snakeheads were found in the non- tidal sections of Dogue Creek, park staff became very concerned and took action to try to protect the central wetland from invasion.

Northern Snakeheads have razor sharp teeth.

In 2006, the Resource Management staff at Huntley Meadows requested staff from the Watershed Planning and Assessment Branch of the Department (WP&AB) of Public Works and Environmental Services (DPWES) conduct an electro-fishing survey of Dogue Creek at the park’s southern tip.  Electro-fishing doesn’t kill the fish but renders them immobile for several seconds, enabling staff to net, identify, and count the fish before releasing them.  With this survey, staff attempted to determine if snakeheads had made the mile and half migration up the creek from the Route 1 overpass where 80 snakeheads had been caught the year before.  Unfortunately, one 17” snakehead was caught inside the park just as the shocking crew was finishing for the day.  Although just one fish was caught, it was evident that snakeheads had made the long upstream migration and were only about one mile below Huntley’s central wetland.

Heather Ambrose, Shannon Curtis, Eric Forbes
and Dave Lawlor shock, net, and count fish in Dogue Creek at Huntley Meadows Park in 2010. No snakeheads were found during this survey.

In 2007, staff conducted another electro-shocking survey in Dogue Creek at Wickford Park, which is about one mile upstream from where the 17” snakehead had been caught in 2006. This section of the migration would be much tougher to navigate due to shallow wetlands that periodically dry up as well as multiple beaver dams that impede migration.  Although no snakeheads were found during the survey, park staff and visitors began to see snakeheads in the central wetland in 2009 and 2010. Two of these fish were very young, indicating snakeheads were either reproducing in the park or immigrating into the wetland from Dogue Creek. 

During the spring of 2011, Huntley Meadows Park patrons and volunteers reported seeing a large snakehead in the central wetland along the boardwalk just past the loop.  Soon reports were coming in almost daily and the snakehead number doubled when two large snakeheads were seen in a ditched portion of the wetland, right on top of the water. Immediately park staff jumped into action and tried to net the fish, but these large fish were elusive.  Park staff became very concerned that the fish would breed in the wetland, potentially releasing hundreds or thousands of baby snakeheads which could take over the central wetland and wreak havoc on the wetland’s incredibly diverse aquatic populations. 

Two large snakeheads were netted in the central wetland at Huntley Meadows Park in 2011.

Shannon Curtis and Chad Grupe from the WP&AB were contacted. These folks live and breathe water quality and are sought after professionals when it comes to fish and anything that lives in Fairfax County waters. They brought their electro-fishing backpacks to the park to try to help catch the two large snakeheads before they started upsetting the wetlands sensitive ecologic balance. Within an hour they caught two large snakeheads measuring 20” and 25”. 

After another hour or two of searching no more snakeheads were located in the wetland and the search was called off.  Both of the large snakeheads were females and they were packed full of hundreds of eggs.  As required by state law, the fish were destroyed.  Staff examined the stomach contents and the large fish’s stomach contained a large goldfish (Carassius auratus) and the smaller fish’s stomach contained a smaller fish or tadpole of an undetermined species due to nearly complete digestion.  

Huntley staff continues to be diligent in the search for more snakeheads and we expect this will be a long-term battle.

Dave Lawlor, natural resource manager, Huntley Meadows Park

The severity of the Northern Snakehead problem was made clear this summer when, during a survey at Old Colchester Park and Preserve, Park Authority staff spotted this dark cloud in a tidal marsh near the Occoquan River. It was identified as a “fry ball,” or a group of 10,000-15,000 newly hatched snakeheads.