Zebra mussels have taken over Rideau River, study finds

A new 26-year study of zebra mussels in the Rideau River clearly shows the tiny invaders have swept through the river and are here to stay.

Long-term study tracked the invasive species' population over 26 years

Zebra mussels like this one have spread throughout the Rideau River. (Supplied )

A new 26-year study of zebra mussels in the Rideau River clearly shows the tiny invaders have swept through the river and are here to stay.

Researchers with the Canadian Museum of Nature first started surveying the zebra mussel population after the species was found in Mooney's Bay in 1990.

In an article published in the Canadian Journal of Zoology on Wednesday, they show how the mussels have effectively taken over the Rideau River.

"The Rideau has what it takes to have them explode in numbers," said Dr. Andre Martel, the study's lead author, on CBC Radio's All In A Day.

"If you go diving, scuba diving in Mooney's Bay, or snorkeling and you just check the bottom, everything is covered by zebras."

Researchers went out every year for 26 years to inspect the zebra mussel population on the river. (Supplied)

Introduced in 1980s

Zebra mussels came to North America on commercial vessels in the mid-1980s and have since spread through lakes and rivers.

Martel said the nutrients in the Rideau River have made it ideal for the mussels. By 1995, the study's researchers had found they were so prevalent that there could be as many as 300,000 of them in a square metre.

They were especially concentrated in the stretch of the river between Manotick and Ottawa, including in the Rideau Canal.  

The researchers sampled the same areas in the river system each year, including regions in the canal that had been drained, to see where the mussels were accumulating.

Martel said they found them growing on top of existing species, many of which they largely wiped out.

"The impact has been severe on our native mussels," he said. "We do have to pay a price when we introduce such an invasive species."

Martel said there are a few isolated spots in the river where native mussels have survived, and the researchers want to perform further studies to see what's allowed that to happen.  

The zebra mussels were also found in large numbers in the Rideau Canal. (Supplied )

Full river impacted 

Initially, the upstream area of the river from Manotick to Smiths Falls, Ont., wasn't as inundated, Martel said, but that has changed. 

"For awhile, we thought our native species would be spared. Unfortunately, this was not so. We had beautiful populations of native mussels and unfortunately we have lost [them]" he said.  

Martel told All In A Day that people should make sure their boats are clean when they take them out of the water to prevent the population from expanding further.

"We spread the beast," he said. "We spread the zebras around."