Posts Tagged ‘invasive species’

Electrofishing for Northern Snakehead

September 28, 2015

Northern Snakehead (Channa argus) is an exotic species of fish (non-native) that threatens to disrupt the marshland ecosystem at Huntley Meadows Park, Fairfax County, Virginia USA.

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 [2014]. 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. Source Credit: David M. Lawlor, Natural Resource Manager, Huntley Meadows Park. Staff Manages Snakehead Threat At Huntley Meadows Park.

On 25 September 2015, Dave Lawlor (shown below, far right) collaborated with a team of staff members from the Fairfax County Department of Public Works and Environmental Services to electrofish for Northern Snakehead in the central wetland area at the park.

Electrofishing for Northern Snakehead (Channa argus) in the central wetland area at Huntley Meadows Park, Fairfax County, Virginia USA.

Electrofishing for Northern Snakehead at Huntley Meadows Park.

The process seemed to be all about teamwork: every member performed a role, beginning with the “electroshockers” (see close-up, shown below) working closely with the “herders” and “dip-netters,” and ending with the “collectors.” [Editor’s Note: Words in quotes are my unofficial terms for each of the roles on the electrofishing team.]

Electrofishing for Northern Snakehead (Channa argus) in the central wetland area at Huntley Meadows Park, Fairfax County, Virginia USA.

Electrofishing for Northern Snakehead at Huntley Meadows Park.

The following photo shows a relatively large Northern Snakehead netted near the berm. Approximately 25 snakeheads were culled from the wetlands, including several measuring at least 18 inches (18″) in length! The entrails will be examined to collect data about the diet of these predatory fish.

A Northern Snakehead (Channa argus) netted in the central wetland area at Huntley Meadows Park, Fairfax County, Virginia USA.

A Northern Snakehead netted in the central wetland area.

The next photo shows Dave Lawlor (shown left) working closely with one of two “electroshockers” in search of snakeheads hunkered down for cover underneath a fallen log.

Electrofishing for Northern Snakehead (Channa argus) in the central wetland area at Huntley Meadows Park, Fairfax County, Virginia USA.

Electrofishing for Northern Snakehead at Huntley Meadows Park.

Coincidentally, an artificial fishing lure was observed along the shoreline not far from the location of the preceding photo. Fishing is not permitted at Huntley Meadows Park. If you see anyone fishing illegally, please call the HMP Visitor Center at 703-768-2525.

An artificial fishing lure spotted at Huntley Meadows Park, Fairfax County, Virginia USA.

An artificial fishing lure.

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Editor’s Note: Mike Powell and I were fortunate to be in the right place when the electrofishing team arrived at the central wetland area; with permission from Dave Lawlor, we enjoyed the extraordinary opportunity to photograph this interesting event. See Mike’s excellent blog post: Snakeheads at Huntley Meadows Park.

Copyright © 2015 Walter Sanford. All rights reserved.

Purple Loosestrife (Lythrum salicaria)

February 10, 2015

Purple Loosestrife (Lythrum salicaria), shown below, is an invasive plant that was spotted during a photowalk along the boardwalk in the hemi-marsh at Huntley Meadows Park on 29 August 2014.

One mature plant can produce more than 2 million seeds annually. Seeds are easily dispersed by water and in mud adhered to aquatic wildlife, livestock and people. Source Credit: Purple Loosestrife, Ecology and Management of Invasive Plants Program, Cornell University.

Park staff members removed these plants soon after I photographed them. If you see this plant anywhere at the park, then please stop by the Visitor Center in order to notify a staff member of your sighting.

Purple Loosestrife (Lythrum salicaria)

Purple Loosestrife (Lythrum salicaria)

Purple Loosestrife (Lythrum salicaria)

Editor’s Note: Thanks to Kevin Munroe, Manager, Huntley Meadows Park, and Matt Ryan, Naturalist, for identifying the flowering plant shown in my photos. I knew the plant was one I’d never seen at the park; I didn’t know it’s an invasive species that spreads rapidly.

Copyright © 2015 Walter Sanford. All rights reserved.

Crayfish

January 15, 2015

Crayfish

Two types of crayfish are known to inhabit the waters at Huntley Meadows Park: a native species; and a non-native species.

We believe our native species is Cambarus diogenes [known as “chimney crayfish”], although we’re not positive about the species. Source Credit: Mr. Kevin Munroe, Park Manager at Huntley Meadows.

The non-native species is “red swamp crayfish” (Procambarus clarkii), according to Ms. Kat Dyer, a long-time volunteer at Huntley Meadows Park also known as the “Crayfish Lady.” Ms. Dyer is now a part-time naturalist at the park.

The crayfish, shown above, was spotted alongside the boardwalk in the hemi-marsh at Huntley Meadows on 24 August 2014. I consulted the local experts for help in identifying the species.

Crayfish are just real hard to ID! You have to have a mature male, and you need to look at the tiny appendages under the abdomen to make a positive ID. My guess is that it’s the [non-native] exotic species since you found it in the wetland rather than in the streams/woods. Source Credit: Kevin Munroe, Park Manager at Huntley Meadows.

Crayfish is an important organism in the wetlands ecosystem food web. Many animals prey upon crayfish, including fish, raccoons, otters, Great Blue Herons, and Great Egrets. Brush shelters (that resemble large, man-made beaver lodges) located in the 50-acre central wetland area provide egg-laying habitat for crayfish.

Copyright © 2015 Walter Sanford. All rights reserved.

Snakehead fish

March 8, 2014

The following photos show a Snakehead fish (Channa sp.) spotted along the boardwalk during a photowalk through the central wetland area at Huntley Meadows Park on 06 September 2013. Snakehead is an exotic species of fish (non-native) that threatens to disrupt the marshland ecosystem at the park. This individual is approximately 12 inches (30.48 cm) in length.

Snakehead fish (Channa sp.)

Snakehead fish (Channa sp.)

Snakehead fish (Channa sp.)

Related Resources:

Copyright © 2014 Walter Sanford. All rights reserved.


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