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Brad Dokken, Forum News Service, Published November 03 2013

North Dakota ramping up inspections for invasive zebra mussels

GRAND FORKS - The North Dakota Game and Fish Department is ramping up its efforts to check for zebra mussels along the U.S. portion of the Red River after the recent finding of the invasive mollusks in Lake Winnipeg.

Despite the news from Manitoba, no new signs of zebra mussels have been found along the Red River since 2011, when a handful of larval specimens were found near Wahpeton, N.D., officials say.

The Red River flows into Lake Winnipeg north of Selkirk, Manitoba.

According to Fred Ryckman, aquatic nuisance species coordinator for the state Game and Fish Department in Riverdale, N.D., adult zebra mussels have never been found in the U.S. portion of the Red River despite fairly intensive monitoring. Water tests confirmed a small number of microscopic larval zebra mussels, called veligers, in 2010 and 2011 near the confluence of the Otter Tail and Red rivers, while none were found last year.

Ryckman said he is waiting for this year’s results from water samples sent to a lab in Montana for testing. The department also submitted water samples from the Sheyenne River and Devils Lake, among other sites, as a precautionary measure, Ryckman said.

He said he expects to have results within a few days.

The stepped-up inspections come on the heels of last week’s announcement in Manitoba, where biologists confirmed the presence of adult zebra mussels at two sites on Lake Winnipeg. Canadian officials haven’t determined the origin of the infestation.

Native to southern Russia, zebra mussels crowd out native mussels and are notorious for clinging to hard surfaces such as docks and boat lifts and clogging water intake structures. Zebra mussels typically are less than an inch long but can reach 2 inches.

On the search

Ryckman said department personnel have begun sampling sites from Wahpeton to Fargo, checking hard structures such as riprap, dams, water intakes, courtesy docks and fishing piers for adult zebra mussels, but none have been reported.

Game and Fish plans to check sites all the way to the Manitoba border, he said.

Zebra mussels have infested upstream reaches of the Otter Tail River watershed in Minnesota, and it’s possible veligers could drift into the Red River that way. Barry Stratton, south district manager of the Department of Natural Resources’ Ecological and Water Resources Division in Fergus Falls, Minn., said adult zebra mussels have been found as far down the Otter Tail as halfway between the Orwell Dam in Fergus Falls and Breckenridge Lake near the confluence with the Red River.

He said the DNR has shifted its sampling focus from larval zebra mussels to adults. Looking for veligers, he said, is time-consuming, and adult zebra mussels almost always show up before veligers are found.

Ryckman said larval zebra mussels drift freely after hatching but must attach to a hard surface to survive. Given that requirement, he said it’s unlikely they could drift the 450 river miles from Wahpeton to Lake Winnipeg without adult zebra mussels showing up somewhere along the way. The amount of silt in the Red also could discourage the mussels from establishing colonies, he said.

“There probably are veligers drifting down the Red River every summer, but it’s kind of a needle in the haystack to sample them and get them unless they’re tremendously abundant,” Ryckman said. “There’s no indication we have them yet.”

Neither Ryckman nor Henry Drewes, regional fisheries supervisor for the DNR in Bemidji, think the zebra mussels in Lake Winnipeg came from the Red River.

“We won’t know for sure, but it sure has the suspicion that it was some sort of overland movement” to Lake Winnipeg, Drewes said.

Ryckman said he’s been in touch with Manitoba officials, who plan to sample the Red River to the U.S. border, checking sites where adult zebra mussels might attach and become established.

North Dakota’s inspections will continue until freeze-up, Ryckman said. If zebra mussels had become established in the Red River, he said industrial users such as American Crystal and municipalities along the river likely would have noticed infestations on their water intake structures.

“It’s not just us looking — it’s up and down the river — and we’ve received absolutely no reports,” Ryckman said. “There’s just no indication.”

No room for error

Ryckman said angler awareness of zebra mussels and other invasive species has improved in the past decade, but there’s no room for error. A hunter who takes too many pheasants or an angler who keeps too many walleyes is breaking the law, but a single act doesn’t have a lasting impact on the resource, Ryckman said.

One slip-up with an invasive species, though, could result in an infestation.

“Unfortunately, it only takes one, and it can be extremely damaging,” Ryckman said.