Accessibility and Access Keys [0]
Each year at this time, the water in Brown’s Inlet in the Glebe erupts. Resident ducks scuttle for the shore, thinking it safer on dry land.
The ponds, fed from the Rideau Canal by underground pipes near Bank Street, become birthing pools for fish, frogs and turtles as well as other fauna that emerge during the canal’s annual refilling, which began Wednesday—three weeks ahead of its official May 19 opening for boats.
Carp, huge and silent among the weeds for most of the year, thrash the surface as they dig egg troughs in the inlet’s sediment. Little helmets of baby turtles appear like green bubbles. When knots of frogs emerge soon after, their chirping can be heard at Lansdowne Park.
This metamorphosis is a common rite of spring for Canadians, watching creatures hatch or crawl out of mud and leaf litter as snow disappears across the country. We can bear the depths of winter because we know a balanced ecosystem always regenerates.
In Ottawa, the story is slightly different. The Rideau Canal is not a natural environment; it’s a manmade waterway that each fall is emptied like a back-yard cement pond, and there’s no guarantee its inhabitants will survive the ordeal.
“I have to admit the canal’s wildlife is not something we pay much attention to. It’s a recreational facility for boaters in the summer and for skaters in the winter. It was never designed to be a habitat for animals,” says Dave Ballinger, director of Rideau Canal operations for Parks Canada—the waterway’s owner.
Parks Canada prepares the canal for winter with the “big draw-down,” a gradual siphoning of water and most everything in it from the locks at the north end of Mooney’s Bay into the Ottawa River downtown.
The canal has been drained for nearly a century to protect its walls and as part of an overall lowering of the Rideau River to save the locks from ice damage. The manmade portion from Mooney’s Bay to the Ottawa River is called the “Canal Cut” or “Ottawa Reach” of the Rideau.
From a biological point of view, this emptying represents a complete environmental collapse. Frances Pick, director of environmental sciences at the University of Ottawa, marvels at how the canal’s fauna endures.
“If you want to apply maximum stress to an ecosystem, take all its habitat away. Yet (the canal) is recolonized every spring with basically the same ecology. That tells me the communities that populate it are very tough,” she says.
In 1970, the National Capital Commission got permission from Parks Canada to lower the water level further and create an eight-kilometre skating rink.
This increased the stress on resident wildlife, yet it might also have made it more adaptable, says Paul Hamilton, research assistant at the Museum of Nature and an expert on the Rideau River ecosystem.
“This stress probably limits the number of species. But you’ve heard the saying ‘what doesn’t kill you makes you stronger’? It’s such a drastic event that animals that don’t—or can’t—migrate would have to adapt or die,” he says.
Draining starts after Thanksgiving (the final recreational boating weekend), generally on the last Monday of October, and takes at least three days. The pace is vital.
“That speed is critically important so fish don’t get stranded out of their pockets of deep water,” explains Ballinger. “Our primary goal isn’t to protect the habitat because it’s artificial, and we know it’s going to be repopulated pretty well intact in the spring no matter what we do. But we are aware that animals like fish may need some special attention.”
Because of its artificiality, no team of scientists maintains the canal’s environmental balance. In fact, biologists tend to ignore it, which means little scientific research is available to help understand why the fish, birds and mammals keep coming back, often to the same locations every year.
While many believe most water-borne residents tend to get swept into the Ottawa River each fall, one of the Museum of Nature’s resident ichthyologists feels that any fish hardy enough to find enough to eat can probably make it through the winter intact.
“It’s both a delicate and non-delicate system. I think if there’s enough nutrients (during winter) and if the water’s deep enough then there’s no reason fish couldn’t spend their whole lives in what amounts to a big, safe, concrete dish,” says Noel Alfonso, the museum’s research assistant for fish studies.
Ballinger says the canal can have pockets as deep as two metres during winter; Dow’s Lake can have depth of up to four metres, which provide plenty of room for fish to survive, especially carp and catfish, which can grow to a reported seven or eight kilograms.
There’s no proof the big, orange-and-white carp spend their entire lives in the canal. Yet there’s something unvarying about their annual occupation of Brown’s Inlet, the Lily Pond at Fifth Avenue and Patterson Creek. Experts believe this is too precise to be a transient lifestyle.
As any grade-school biology student can tell you, fish tend to return to familiar spawning grounds. This means some of the canal’s carp probably never leave the system and have somehow imprinted at least one difficult spawning route—through Brown’s Inlet’s underground pipes.
It’s more likely that smaller fish—crappies, blue gills, pumpkin seeds and smallmouth Bass—follow the water’s flow each fall and are flushed into the Ottawa River, to be replaced with a new population from Mooney’s Bay once the locks start operating.
Yet some of these sunfish species do spend the winter in the Canal Cut. The proof comes in early June when the canal’s surface can become awash in small, dead fish.
“The oxygen and light levels in spring are fine, so this (kill-off) probably has to be of fish that spend winter under the ice and just don’t survive, for whatever reasons,” says Pick.
Other water dwellers such as minnows, clams, mussels, shrimp and micro-invertebrates survive winter by simply digging themselves into the canal’s mud and waiting for spring.
Surface dwellers have a different story when the days become short and chilly. Birds migrate, except for a small, resident duck population that spends the winter around open patches of water on the Rideau River, especially near the Bank Street bridge.
Ballinger says geese and cormorants tend to use Dow’s Lake as a rest and feeding station during migration and are more transient. But there’s one bird that causes the experts confusion.
He’s a blue heron, nicknamed Moe by some residents around Patterson Creek, one of his favourite feeding grounds. He also feeds and, reportedly, spends evenings at the Experimental Farm’s arboretum.
Pick believes the heron is a solitary male who migrates up from the southeastern United States in April to a breeding colony along the Rideau River. Once his procreative duties are done, he glides into Ottawa, back to the spots he’s been seen at for years. One reason is because his hangouts seem to produce little competition for the invertebrates and minnows that make up his diet.
Blue herons can live more than 20 years, so it’s possible Moe has been around for many years.
Muskrats appear to be the waterway’s only resident mammals, many raising their young in the grass marsh at Dow’s Lake, in Brown’s Inlet and in Patterson Creek as well as in the backwaters between Mooney’s Bay and Hartwell Locks.
Charles Billington, director of community relations for the Rideau Valley Conservation Authority, says muskrat could spend winters in the canal if they were able to find space, after draw-down, to build reed lodges on dry ground.
“I know some do because last winter I was skating and saw one on the ice. That probably means it would have come up through a hole in the ice, which means its lodge wasn’t far away,” he says.
Like birds, most other wildlife react to fall’s dropping water level as a sign to leave. These include beavers, foxes, mink and otters. “Anything that stays better know how to hibernate really well,” Billington says.
For five months, life in the canal is dormant. But it’s still quite alive.
By late March, even before the ice is fully thawed, Dow’s Lake’s waterfowl start feeding on early plants, gaining strength to look after the young they hatch during May in the reed marsh just west of the lake. The early start is also to get broods on the water before predators return to drink at the shoreline.
The canal’s refilling at the end of April can take less than three days because fish are already moving through the system, feeding on minnows and invertebrates churned out of the sediment by water movement.
As the days get longer and warmer, canal life returns to normal, as if the ecosystem had been lifted out and returned intact. The ecosystem’s artificiality makes regeneration easy to follow; as in most cement ponds, weed growth leads the curve.
Judging by the explosion of Asian milfoil, the canal is extremely rich in nutrients, says Hamilton.
Despite its unattractive appearance, the weed is a major factor behind the habitat’s health.
“It took over in 1996, and I know the NCC gets lots of complaints about it. But it’s a great habitat for fish and birds,” says the researcher, who is taking part in a project to replace milfoil with cap grass, which doesn’t reach the surface.
Pick analyses the canal’s vegetation from a more scientific view, explaining that all standing bodies of water have to go through a “phase shift,” which means becoming dominated by macrophytes (weeds) or by algae.
“Even though people don’t like (milfoil), I think the overall habitat is better because of it. You’re either going to get it or algae unless you use chemicals. I can’t see people preferring goopy algal blooms, can you?” she asks.
Without the buffering and filtering abilities of pests such as milfoil and zebra mussels, the water wouldn’t be as clear and toxin buildup in the sediments on the canal floor might limit the amount of wildlife the waterway attracts.
“The fact that it repopulates so quickly and completely after winter is a sign of how healthy it is, just as it is,” says Ballinger.
It’s this health that makes the canal such a wonderful neighbourhood border, bauble and backdrop for much of Ottawa’s recreation and tourism.
Despite its seeming durability, the ecosystem is completely ephemeral. The water is more basic than the Rideau River, upon which it depends for much of its flora and fauna, and restricted water flow means there is limited self-cleaning.
Yet right now, like every year, Brown’s Inlet and Dow’s Lake surge with new life as if the canal’s emptying and refilling were as natural as the seasons.
Mike Levin is an Ottawa writer.
© The Ottawa Citizen 2006