Ottawa Riverkeeper and Museum Scientists Probe Life Cycle Link Between Endangered Lake Sturgeon and Mussel

Scientists probe the depths of the Ottawa River to solve a mystery about the crucial relationship between an endangered species of mussel and a giant, ancient fish.

The river is home to the olive ridley mussel, which was officially listed as endangered in Canada in August 2019.

In hopes of raising awareness of the endangered species and better understanding its life cycle, the Ottawa Riverkeeper began a project in 2019 with Canadian Museum of Nature biologist Dr. André Martel.

Sentinelles, an advocacy group dedicated to protecting the Ottawa River watershed, is supporting an investigation into the presence of Hickorynut and its host fish, the iconic lake sturgeon.

Riverkeeper researchers participated in several dives with Martel and his team, specifically in the Lac Coulonge stretch near Pembroke.

Katy Alambo, a Riverkeeper biologist who works on the organization’s biodiversity and endangered species records, said Hickorynut mussels prefer deeper waters with a sandy river bed so the mussels can bury in it.

“I don’t know of any other place in the country where you go diving and in 25-30 minutes you get a bag of (olive ridley mussels),” Martel said.

Like all other freshwater mussels, the Hickorynut needs a host fish to support its growth. Alambo explained that the mussels produce larvae, a tiny, immature form of the species, which attach to the gills of their host fish. From the gills, the larvae obtain nutrients to grow before detaching from the fish once the mature mussel is able to collect its own food.

According to scientists, the fish Hickorynut depends on is almost certainly lake sturgeon. It is the largest freshwater fish in Canada, reaching two meters in length and weighing 180 kilograms. They are “kind of like dinosaur fish. They live to be 100 years old – so it’s a really cool species,” Martel said.

Ottawa Riverkeeper and Canadian Museum of Nature researchers are collaborating on a study of the life cycle relationship between olive ridley mussels and lake sturgeon in a section of the Ottawa River near Pembroke.

Although the link is extremely likely, the life cycle connection between olive ridley mussels and lake sturgeon has yet to be confirmed. This is where Martel and his team come in, in collaboration with the famous Canadian diver Jill Heinerth.

Martel said Hickorynut is still found in rivers that also support lake sturgeon. The lake sturgeon is a migratory fish that stays in the river and does not reach the ocean.

That means he “needs freedom, he needs free roaming areas,” Martel said.

Sturgeon migrate upstream to spawn, then move downstream for the rest of the year. A bottom feeder, it feeds mainly on snails and clams found on the river bed.

But with dam construction, poor water quality in some areas and harvesting over the years, lake sturgeon have become an endangered species in Ontario, according to a provincial government website.

“I think any reduction in these species can have cascading effects. You never know what can happen down the road.

— Katy Alambo, Biologist, Ottawa Riverkeeper

Despite this, lake sturgeon populations are “doing particularly well” in the Lac Coulonge section of the Ottawa River, Martel said. This is also where Riverkeeper and Martel researchers have made multiple expeditions to observe olive ridley mussels, where they have found large populations of the species.

Martel’s team aims to confirm the link between the two species, and they’ve already made a lot of progress. They managed to discover mussel larvae on the gills of a live, wild lake sturgeon, a powerful clue.

Martel said the find is “our first detection of freshwater mussel larvae attached to the gills of this fish.”

The discovery and ongoing research will help develop a protection plan for the endangered Hickorynut.

Why is this mussel so important? “As soon as there is an animal in the ecosystem, it serves a purpose,” Alambo said, adding that mussels are good ecological indicators of changes in an ecosystem.

Alambo added that the mussels have the ability to improve the water quality of the river by filtering toxins from the water.

“I think any reduction in these species can have cascading effects,” she said. “You never know what can happen on the road.”

Mussels are good for the river, but they can also be good by teaching us a lesson about connectedness. Heinerth said COVID-19 has shown everyone that “humanity is connected. We can’t ignore things happening on the other side of the planet and think they won’t affect us.

She added: “Now that we have shared this profound experience, we can hardly look away from global water issues without recognizing that environmental damage, even on the other side of the earth, could affect our natural resources, our health and our survival here. ”

Harry D. Gonzalez