Invasive Mussels

This undated photo shows a group of zebra mussels. Wyoming Gov. Mark Gordon has convened an emergency panel to scrutinize algae balls and other aquarium products amid concern that the invasive mussel species could have found an unexpected route into state waters.

CASPER – Although a highly invasive and harmful mussel was unexpectedly found in aquarium decorations at Wyoming pet stores earlier this year, wildlife officials say they have not yet detected zebra mussels in state waters.

“Right now, we are negative for zebra and quagga mussels in the state,” Alan Osterland, chief of fisheries for Wyoming’s Game and Fish Department, told the Star-Tribune.

Colorado, Montana, Idaho, Washington and Oregon are also negative, Osterland said.

If zebra mussels were to proliferate, they would be harmful to Wyoming’s infrastructure, in large part by clogging up water delivery systems. And because the animals are filter feeders, they have the ability to filter out plankton that other species need to survive.

That damage wouldn’t take much time.

Zebra mussels are “extremely reproductive,” Osterland said.

One female can lay up to 1 million eggs a year. The eggs are often microscopic, making them difficult to detect in their first year of life.

“Agriculture stands to lose a lot if zebra mussels become established in the state of Wyoming,” Doug Miyamoto, director of the Wyoming Department of Agriculture, told lawmakers at a recent Joint Travel, Recreation, Wildlife and Cultural Resources Committee meeting.

In early March the Wyoming Game and Fish Department announced it had detected zebra mussels in decorative “marimo balls” or “moss balls” at four Wyoming pet stores.

The discovery surprised wildlife officials, who for years have worked to keep the invasive species out of Wyoming waters through boat inspections.

Officials worry the mussels could end up in Wyoming waters or treatment systems when an aquarium owner changes tank water.

The moss balls are no longer sold at pet stores in Wyoming, but other aquatic and semiaquatic plants are. If the plants that are still sold in pet stores are shipping internationally, they will be inspected at the ports for any foreign bodies.

“So far we don’t have any indication that we’ve identified zebra mussels in connection with other nursery stock type products in the state,” Miyamoto said.

Online sales of the moss balls are also highly limited because of the threat of zebra mussels, which has given rise to what Miyamoto called a “black market.”

“They’re so popular that they are being sold in underground markets,” Brian Nesvik, director of the Wyoming Game and Fish Department, said in the same committee meeting.

Because people often dispose of their aquarium water through drains, Game and Fish and the Department of Agriculture are monitoring sewer systems for proliferation of the invasive species.

So far there is no evidence of the mussel in the wastewater treatment systems, but there’s also no evidence to suggest that the mussel is unable to survive in the system.

“In the case of this situation with the moss balls, if we get a positive on a wastewater facility, it would mean we would ramp up monitoring at that facility,” Osterland said in an email.

One way the departments monitor and test water is through environmental DNA technology. The highly sensitive tool can be used in flowing and standing water to detect whether or not a certain species is present.

The technology is so sensitive that it may produce a positive result even if the species is dead. If that were to occur, follow-up testing would ensue.

State efforts go beyond testing. Boats and other watercraft have to go through mandatory inspection and possible sanitization before entering Wyoming’s waterways, particularly if the watercraft came from out of state. Once the boat is inspected, people receive a receipt as proof of inspection.

Failing to get a boat inspected can result in citations.

In 2020, the Game and Fish documented 226 people who failed to stop at aquatic invasive species checkpoints. About half were given warnings and half were given citations, according to Richard King, chief of Game and Fish.

“I believe we have a solid set of regulatory hurdles in place to prevent the transfer of what we know so far about zebra mussels and their pathways. Our state will have to remain vigilant to prevent future importation of these mussels,” Miyamoto said.

Managing Editor Rebecca Huntington has worked for newspapers across the West. She hosts a rescue podcast, The Fine Line. Her family minivan doubles as her not-so-high-tech recording studio.

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