December 06, 2007
Eric McGuinness]
The Hamilton Spectator
Cootes Paradise is carp-free for the first time in years, which means plants in the 250-hectare marsh will again have a chance to grow undisturbed.
A decade-long effort to get rid of the destructive alien species ended successfully when a strong west wind and the low level of Lake Ontario combined to push all the water in Cootes -- and all the fish -- through the Desjardins Canal into the main body of Hamilton Harbour last week. Royal Botanical Gardens staff lifted a grate in the carp-exclusion fishway to let them out. With the grate back in place, the destructive carp can't return.
Tys Theysmeyer, aquatic biologist for the RBG and leader of Project Paradise that aims at restoring a healthy ecosystem in the shallow Cootes wetland, is as excited as a kid opening presents on Christmas morning.
"It's been a tremendous struggle to get them out of there. Next spring the marsh will be fantastically different," he said this week. "I want to enjoy winter, but I'm so looking forward, I can't wait for spring. Fragile aquatic plants will finally get a shot."
Most carp and other fish that spawn in Cootes migrate to the deeper harbour in winter, but some have remained behind since the fishway went into operation in 1997. A population once as high as 70,000 adults was reduced about 1,000 in recent years, but high water levels let them overwinter and reproduce in the marsh -- until now.
Carp are bottom feeders that uproot plants and stir sediment, making the water cloudy, which further hampers plant growth. Ben Porchuk, new head of conservation at the gardens, says their absence is key to restoring the lush vegetation that once covered Cootes.
"It should give us a taste," he said. "I'm just salivating at the prospect of the richness that will come back."
Theysmeyer started studying Cootes for the federal Department of Fisheries and Oceans in 1994, gathering information for the Hamilton Harbour Remedial Action Plan, drafted to get the bay off the International Joint Commission's list of toxic hot spots on the Great Lakes.
He was hired by the RBG in 1997, has worked since on Project Paradise and watched anxiously as a windstorm herded the last carp toward the Desjardins Canal last Wednesday.
"The wind pushed out the last eight inches (20 centimetres) of water, leaving just wet mud across most of the marsh, but the last carp were extremely stubborn about leaving. The water was too muddy to see them beneath the surface, but at the same time too dirty for them to stay under, so they were porpoising up out of the water in front of the carp barrier in the hundreds.
"We had removed one of the larger exclusion grates and were trying to herd them out. At sunset, when they were within 50 feet (15 metres) of the barrier, I put on my boots and tried to spook them. The water was rushing out and they were resisting, but they were all gone the next morning.
"I'm sure there's the odd one left in a deeper pool, but we're basically carp-free. If there are a couple of little ones, they won't be able to reproduce."
Theysmeyer said Cootes last drained empty in 1965 and before that in 1935.