With the detection in 2019 of zebra mussels in Lake Ashtabula - a 5,000-acre impoundment stretching for more than 12 miles north of Valley City, smack dab in the middle of the Sheyenne River system which drains much of southeastern North Dakota - the impacts were felt on all levels. From sudden questions regarding sustainability and restrictions on the local fishery, heightened efforts by the state Game & Fish Department (NDG&F) to determine the extent of the infestation, and ultimately the losses from redistribution of game fish reared at the U.S. Fish & Wildlife Service’s (FWS) federal fish hatchery downstream, the effects punctuated summer with red flags and remedial efforts and served as a stark warning for other waters in the region.
While not the first invasive in the water system – curlyleaf pondweed was discovered in the Sheyenne below the dam two decades ago, and common carp have long been established in the flow – zebra mussels brought headline-grabbing attention which continued throughout the open water season and on into fall when local cabin owners began to pull their docks and boat lifts from the water. For those on the downstream end of the reservoir near Baldhill Dam, the late-summer ritual confirmed what the NDG&F discovered in June, as hundreds of the razor-sharp fingernail-sized mollusks appeared as strings and mats colonizing the metal and plastic with their feathery byssal fibers.
After the discovery, state agency quickly flagged the lake as an infested water on its website and posted signs at every launch stressing that fact and the extra care and required in the cleaning, draining and drying of watercraft which anglers and recreational boaters would need to do in order to prevent transfer of zebra mussels and their near-microscopic veligers in bilge, livewell and hull water taken on when using the lake. With nearly 2 million fingerling walleyes set to be stocked around the state and into neighboring jurisdictions over the summer, the FWS and the NDG&F out of an abundance of caution aborted mission - despite no detection of veligers in the hatchery water supply - and stocked the abnormal abundance of walleyes into Ashtabula. The heightened filtration system for the facility to conduct 2020 rearing activities while eliminating the possibility of mussel larvae in the ponds cost more than $100,000, not counting the significant labor and testing activities. Unfortunately, the NDG&F saw little increase in their young-of-the-year sampling, despite the surge of stocked fingerlings following incident.
“We didn’t really see much of a bump in our age-zero walleye survey last fall,” noted BJ Kratz, NDG&F Southeast Fisheries Supervisor, on the unusual influx of walleyes, “we didn’t see a lot of indication that all those extra fish helped,” he concluded, based on the results of the agency’s test netting.
The 2019 infestation of Lake Ashtabula serves as a stark reminder of the nature of aquatic nuisance species (ANS). While they seem to show up out of the blue – a jumping carp here, a sharp shell there – the initial find is usually the tip of the iceberg and a signal that more of the unwanted species are likely in a given water and have been there for a long time. Most often transplanted from personal watercraft like fishing and pleasure boats that move easily from lake-to-lake and state-to-state in the summer, these species find a foothold long before they’re seen on a dock tire or drug up on an anchor.
“Some common impacts observed in lakes are clear water, a shift of nutrients to the lake bottom which causes an increase in plant growth and benthic macroinvertebrates; some lakes see an increase in harmful algae blooms,” said Ben Holen, NDG&F ANS Supervisor, adding, “zebra mussels are really masters of manipulating food web dynamics…taking those nutrients that would be in the top of the water column for zooplankton and things of that nature that young-of-the-year fish need to feed on.”
For those invasives like zebra mussels which can outcompete young gamefish for vital plankton and other food sources, the fishery and financial impact required to prevent further spread is evidenced in the man hours and physical work of posting signs and updating regulations online and in print and creating public-facing media. The battle to slow the expansion has caused many states, and as of the 2019 legislative session, North Dakota as well, to implement new funding sources which tap angler dollars to help fund the fight. With the enactment of SB 2293 in April of last year, a two-dollar ANS fee was added to each resident license purchased after April 1, 2020 and three dollars for every non-resident angling and waterfowl license sold after that date. Additionally, a $15 fee was added to each three-year resident boat license issued in North Dakota and a $15 annual cost has been tacked on for non-residents who must obtain and display a North Dakota ANS sticker on the side of their watercraft before it hits the water each season.
“It’s still important whether you’re a non-resident or resident to clean, drain and dry your boat in between launches,” Holen advises, “be vigilant and know what water bodies you’re recreating on, so if you’re a non-resident, take time to look up the ANS regulations, because they might be different from water body to water body, and `they might change, just be aware,” he added, stressing that North Dakotans are subject to different regulations in other jurisdictions and need to know what they could be bringing back with them to their favorite waters in the Peace Garden State.
Holen stresses that the activities to prevent the spread of ANS remain simple and effective - and with a little common sense and attention to what lakes harbor invasives - are easily conducted each time a boat comes out of a lake or river. Cleaning any dirt, mud, vegetation or other natural debris from trailers, motors and anchors is the first step in removing any unwanted hitchhikers that could be transplanted to the next flow via some very visible means. Draining any water from the many possible storage points, including the hull, livewells, bait buckets and bilge system is the second step that takes care of those smaller forms of ANS, which can live by the dozens in a single drop of water. Pulling the drain plug for transport of watercraft is a requirement in North Dakota and helps assure that those tiny species like juvenile mussels, spiny water fleas or fragments of invasive plants, don’t have a place to hide out. Allowing a boat four days of drying time before it is launched into a new water ensures that any invasives hiding in the nooks and crannies of the craft are dead or no longer viable. In the absence of that turn around time, Holen recommends rinsing out the boat with high-temperature water of 140 degrees or more for the hull and 120 degrees or hotter for livewells and baitwells in a boat. Conducting the clean-drain-dry process with each trip will prevent most instances of ANS transference and ensure the slowed spread of invasives into the state’s waters, ultimately ensuring each angler that it wasn’t his or her inaction the changed a favorite fishery forever.
For more information on preventing the spread of ANS, a listing of infested waters and a copy of the newly-enacted ANS rules and licensing requirements for resident and non-resident watercraft, visitgf.nd.gov/ans.
Nick Simonson is an outdoors journalist who also serves as a Director-at-Large for the North Dakota Wildlife Federation. An avid multi-species angler, upland hunter and volunteer coach for his six area high school trap shooting teams, he resides in Bismarck, ND, with his wife Angie, sons AJ and Jackson, and his yellow lab, Ole. To read more from Nick, visit northdakotawildlife.org.