How an endangered minnow stops Halton Hills in its path
The Redside Dace, a little-known minnow that leaps from water to eat bugs, wields plenty of power as an endangered species in Ontario.

TheStar.com
Aug. 11,2017
Rob Ferguson

This little-known minnow has a lot of power and not just because it leaps out of streams to gulp unsuspecting flies and other annoying bugs.

The Redside Dace, an endangered species notable for its red stripe, has stopped the Town of Halton Hills from finishing a pathway and bridge over Silver Creek in the Hungry Hollow ravine near Georgetown since 2013.

With a little help, of course.

“They really fly out of the water to grab insects,” says Mark Heaton, a biologist with the Ministry of Natural Resources and Forestry, which is working with the town as it develops a plan to complete the path while protecting the habitat for the tiny fish.

“It’s like the canary in a coal mine,” adds Heaton.

In the last few decades, Redside Dace in this region have retreated from their traditional homes in rivers and streams feeding into Lake Ontario from Bronte in the west to Pickering in the east, chased north by development and pollution from urban areas and agricultural runoff.

“It’s not as common or as well distributed as it used to be,” says Jon Clayton, an aquatic biologist with the Credit Valley Conservation Authority who has used a GoPro camera – and a lot of patience – to capture the fish in action.

Now they are found only in the upper reaches of the GTA, at the top end of their natural range.

There’s nowhere to go from there, except extinction.

The fish, which grow up to 12 centimetres long and can jump as high, were added to the endangered species list in 2009, meaning the threat to their survival is imminent.

“There have been drastic declines in this fish,” says Emily Funnell, a biologist and resource management supervisor at the ministry, which has the final say on a permit to allow the path and bridge work to go ahead.

“They require very clean and cool water. It’s an important overall indicator of environmental health.”

It’s not unusual for the government to take strong steps to protect species at risk, such as last April’s ban on hunting snapping turtles.

Halton Hills recently hired an ecological consultant to shepherd the pathway project with suitable protections and safeguards.

“We want to ensure that any proposed trail does not impact the Redside Dace minnow, or any other endangered species. So work is on hold at this time,” says Kevin Okimi, manager of parks for the town.

Development threatens the Redside Dace because of the way they feed.

Even with big eyes and bigger mouths with protruding lower jaws, they can’t see the insects in the air or vegetation above if the water is clouded with sediment, says Clayton, who maintains the fish are doing everyone a favour.

“I don’t think anyone’s going to complain about fish eating black flies. They do provide some control in terms of insects.”

The ministry is awaiting a path and bridge development plan that will mitigate any disturbances to the fish, which are found in pools and slow-moving areas of small streams. They prefer gravel-bottomed areas with overhanging grasses and shrubs.

“You want to create conditions that improve the status of the species,” says Funnell, the main thing the ministry is seeking in Halton Hills’ plan.

“It’s like going above and beyond,” she adds, calling the Redside Dace “an important part of Ontario’s biodiversity. They are part of the larger aquatic food chain.”

Outside the GTA, the Redside Dace are found in some tributaries flowing into Lake Huron, the Holland River into Lake Simcoe and Irvine Creek, a tributary of the Grand River that drains into Lake Erie.

They are also found elsewhere in the Great Lakes and as far away as Minnesota and Kentucky.

In his job tracking fish populations, Clayton has noticed other changes lately, including declines in brook trout, a popular target of anglers.

“This is an indication of stream health and temperature,” he says. “That gives us some concerns about the health of the environment.”

One fish he has not been happy to see further north in headwaters of rivers is the round goby, an invasive species that has been migrating up from Lake Ontario.

“They eat the eggs of other fish and compete with native fish for food.”

The round gobie was discovered 27 years ago in the St. Clair River south of Sarnia, likely from ballast water released by European freighters, and have since been found throughout the Great Lakes basin.