By Steve Chaconas

Potomac River invasive species discussions have focused on hydrilla, Northern Snakeheads and Blue Catfish. Now it’s Water Chestnuts. On a snakehead-shocking trip last summer Virginia Department of Game & Inland Fisheries (VDGIF) biologist John Odenkirk observed a small patch of Water Chestnuts thriving in Pohick Bay off the Potomac River. “When we passed by the bed last year during an electrofishing run, we knew it was different and unusual but did not know what it was. Thus, we collected a sample and returned to the office.” A few minutes and texts later, Odenkirk verified the presence of Water Chestnuts. “I was astonished since I’d heard so many bad things about it. However, there was no mistake, nothing looks even close, and it’s very unique.” Knowing the plant’s problematic Potomac history, he quickly organized a group to pull it out to haul to a compost area. In one afternoon these efforts netted 3.6 tons. Herbicide and mechanical removal, including manually pulling are the best ways to eradicate. The Pohick patch was relatively small and isolated. Odenkirk said, “Everyone we spoke with, including Maryland Department of Natural Resources currently dealing with several similar small outbreaks, recommended manual removal.”

Water Chestnut is a rooted, aquatic plant with both floating and submersed leaves. Floating leaves form a green, glossy and triangular pad with toothed edges. Submersed leaves are feathery and wound around cord-like plant stems up to 16 feet long. This annual plant, spreads by seeds produced in July. Mature seeds are green to greenish brown and sink, remaining alive in sediment up to 12 years! Floating black nuts won’t sprout. This invasive is not the same water chestnut found on Asian menus!

Since last year, Odenkirk and volunteers from VDGIF, Bureau of Wildlife Resources and Complimentary Workforce, U.S. Geological Survey, Fort Belvoir Environmental Services, Interstate Commission on the Potomac River Basin, Northern Virginia Regional Park Authority along with others have monitored ground zero near the Pohick Bay boat launch. “Although the Virginia Department of Agriculture and Consumer Services has legal authority over noxious aquatic weeds, that agency has not previously been active in management of invasive or nuisance aquatic plants.” Again this year, volunteers waded to hand pull and load water chestnuts to be hauled away. This year the same area produced 5.8 tons, nearly double last year. A few nearby small patches indicate the spread of this highly invasive plant.

But hydrilla and milfoil were supposed to be bad. These invasives cleared the Potomac, providing largemouth bass habitat. According to Odenkirk, while some fish use dense water chestnut cover, the plant’s structure blocks all sunlight and doesn’t allow much room underneath. Every nonnative is different. “Some can cause great ecological and economic damage depending on how they interact in newly colonized waters. Although it’s still too early to say with certainty Northern Snakeheads are not an issue (or less of an issue); it certainly seems likely that chestnut has the greater potential to cause harm, based on history and its proclivity to form extraordinarily dense, impenetrable mats.” Navigating or fishing is impossible in waters with full chestnut bloom.

In 1923 a 2-acre Water Chestnut patch appeared near Washington, D.C. In just a few years, it covered 40 river miles. In 10 years, by 1933, dense beds had spread from D.C. to just south of Quantico, VA, covering 10,000 acres! Native grasses were depleted as the invasive took over. One acre of water chestnut produces enough seeds to cover 100 acres the following year. The U.S. Army Corps of Engineers engineered a massive removal effort from 1939 to 1945. Hand removal lasted until 1965. Water Chestnut removal cost an estimated $2.8 million (converted from 1950 to 1992 dollars). Most southern states, including Maryland, have banned all water chestnut species sales to help control distribution.

Volunteers are needed. Odenkirk predicts several years of monitoring the site to reduce the seed bank through attrition. “Last year, we were too late in removal and allowed seeds to mature. This year, we beat seed drop; so next year’s chestnut footprint should be smaller and smaller each year until gone.” Recreational Potomac enthusiasts can assist in the eradication of Water Chestnut by learning what the plant looks like, and to be on the lookout for it. Photos and GPS coordinates should be reported to VDGIF.

Potomac River Bassing in SEPTEMBER

Target thick grassbeds with hollow frog, toad and mat-punching fishing!

In clear and calm water with overcast skies, fish open areas without grass. Use Lucky Craft Gunfish walkers and G-Splash poppers. Walk the dog with Gunfish and don’t stop when fish strike! They will come back. For poppers, pop and stop, varying retrieves until a cadence produces. Try Mann’s Waker over cover.

Mann’s Hollow NEW Goliath frogs on 60-pound GAMMA Torque Braid are perfect over matted grass. Also try toad style soft plastics with a Mustad Ultra Point Swimbait hook. Weighted hooks allow baits to go faster and cast further! Follow-up with weightless stickworms like Mann’s 5-inch HardNose Freefall worm on 10-pound test GAMMA Edge Fluorocarbon line for missed bites! Wacky rig with 2/0 Mustad RED Octopus hooks.

Round Valley ¾ to 1-ounce Tungsten weights with 60-pound Torque braid and a strong Mustad Grip Pin Flippin hook, punch through thick grass mats.

Mann’s Baby 1-Minus crankbaits, in craw and baitfish patterns work over wood and grass. For line, 12-14 pound test Edge on a KVD Quantum cranking rod. Mann’s Reel N’ Shad is deadly this time of year.

Pitch Mizmo tubes on 3/0 Mustad Tube hooks on 14-pound Edge to docks and wood at higher tides, and then grass during every tidal phase. Use scents like garlic Jack’s Juice Bait Spray. Also try swimming jigs like Mann’s Stone Jigs with a HardNose Reel’ N Shad around cover.

Author Capt. Steve Chaconas is Potomac bass fishing guide & contributing writer for BoatU.S. (BoatUS.com) Potomac River reports: nationalbass.com. Book trips/purchase gift certificates: info@NationalBass.com.