Montana has dive team to search for aquatic invasive species

Zebra mussels can compete with native species for food and habitat, cut the feet of swimmers, reduce the performance of boat motors, and cause expensive damage to water intake pipes. (Photo by Brian Peterson)

BILLINGS, Mont. — Aquatic invasive species are like the COVID-19 of streams and lakes. It takes only one watercraft to become a super spreader, introducing an invader like Eurasian watermilfoil or zebra mussels to a waterway.

When an invader is detected, Montana Fish, Wildlife and Parks now has an “A Team” it can call. Last year the group created a six-member dive team pulling volunteers from across its Aquatic Invasive Species staff.

Prior to that, the agency used the U.S. Fish and Wildlife Service’s divers for mussel-type events, but it can take time for them to assemble and drive to Montana when time is of the essence.

“We thought it would be nice to have a quick response dive team, not only for mussel detection,” said Stacy Schmidt, leader of the crew.

“There’s a lot of interest in using the dive team for population delineation of other species, control work for mussels and whatever fishery needs might come up, such as fish counts,” she told The Billings Gazette. “It just seemed like it might be of great value for all of fisheries.”

FWP’s aquatic invasive species program is pretty broad, said Liz Lodman, AIS information officer. In addition to watercraft inspections, the group does education and outreach, AIS detection and prevention, water sampling and laboratory analysis. With the dive team’s help, the staff is also working on eradication.

Beaver Lake near Whitefish has been the subject of a dive team project with partners to eliminate invasive Eurasian watermilfoil. By anchoring mats to the bottom of the lake, the crew is attempting to choke out the weed before it spreads.

“We’re trying to nip it in the bud,” Lodman said.

“Every year we have to go in and check the mats,” she added, to make sure they are still secured and covering the target area. “It’s a fairly low-cost way of dealing with an invasion like this.”

Watermilfoil has become such a problem in some Midwestern and Eastern lakes that companies have been formed just to remove the weed. Michigan-based Aquatic Plant Management, founded in 2012, employs a team of 20 divers for the task.

Having weed-choked lakes is not only bad for a lake’s fish and other inhabitants, it can also lower property values for lakeshore owners by up to 16%, studies have shown. No one wants to buy a cabin on a lake where the weeds are so thick you can’t drive your boat through them.

The cost to the United States of these water-borne intruders has been estimated at $137 billion a year, according to FWP.

In addition to removing aquatic invasive species, the FWP dive team is also working to identify underwater plants and invertebrates, often in water that is cold (40 to 60 degrees depending on depth) where visibility is limited.

“We don’t have great water quality” when it comes to visibility, Schmidt said.

That requires divers to be careful to not stir up sediments and silt that might further cloud the water. It is especially important when working in shallower waters, where most of the invasive species are found. To help out in those situations, the team will use air tanks rather than snorkeling if they are at depths of 15 feet or working around docks.

This year the AIS crew added a specially designed sled that it pulls along a lake or pond’s bottom. The sled carves off the top layer of silt which is then rinsed and sieved to search for aquatic invasive species. The sled was tested in Billings’ Lake Elmo this year.

“It samples a large area quickly,” Schmidt said.

The combined work of the AIS team has paid off. Last year inspection crews checked more than 109,000 watercraft and intercepted 16 fouled with mussels and another 170 transporting aquatic weeds.

This year the numbers of inspections has increased to more than 128,000, Lodman said, as more people were recreating outdoors during the COVID-19 pandemic. Out of those inspections, more than 30 were infested with an invasive species.

“The latest was two jet skis from Minnesota,” Lodman said. “It was amazing how many mussels they had on their boats.”

The personal watercraft were being towed from where they had been purchased for winter storage in Whitefish, she added.

Out of more than 4,300 water surveys this year, FWP has logged 98 AIS detections. The most common species found has been curlyleaf pondweed.

So far, the combined efforts have helped keep Montana waterways at a low rate of AIS infestations compared to other states.

“The more tools we have the better,” Schmidt said.

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