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The massive carp kill currently happening in many of the Kawartha lakes could perhaps be better understood by looking at how the problem has been dealt with in the past.
Last August, more than 1,000 catfish died along a 40-kilometre stretch on the Ottawa River between Cheneaux Falls, near Portage-du-Fort to below the Chats Falls Dam near Arnprior.
Doug Skeggs, special projects officer with the Ministry of Natural Resources in Pembroke, said while there were no long-term impacts, there were short-term challenges.
Similar to our carp problem, Skeggs said the final diagnosis was that the catfish were killed by flavobacterium columnare disease, caused by columnare bacteria.
“That bacteria is always out there. It’s naturally present in our environment,” Skeggs said. “Water quality and water temperature, for the most part, are the causes and it’s all related to weather.”
Skeggs said around 4,000 to 5,000 catfish were killed.
Contrary to many news reports at the time, Skeggs said only catfish were affected.
At the height of the die-off, Skeggs said the ministry got calls from people anytime they stumbled on a non-human corpse, fish or otherwise.
“We investigated every report of species other than fish, and there were a couple reports of turtles, dogs and birds,” Skeggs said.
“Not one of the reports was related to the fish kill.
“It was exclusively fish who were affected and it was almost exclusively channel catfish. And it was primarily a very specific age range of catfish, juvenile.”
The problem lasted for around three weeks in Ottawa, Skeggs said.
The root cause of the kill had everything to do with weather, Skeggs said.
Shortly before the fish kill last year, Skeggs said some extreme weather, such as heavy rain, dumped nutrients into the river.
Skeggs said that change in water quality caused the bacteria to “take off.”
“There was also an extended period of very hot weather that allowed the river water, at least in the surface areas, to rise to the point where it reached a threshold temperature where this bacteria did very well,” Skeggs said.
“Heavy rainfall, just as a natural process, puts a lot of water on the ground and it all rushes into creeks and streams, which rush into big rivers like the Ottawa.”
As that water flows into the river, so does sediment and nutrients from the soil, Skeggs said.
“And that changes the water quality. It changes the chemical make-up of the river,” Skeggs said. “It can affect things like the amount of oxygen available to fish. It can affect things like how much algae is growing and decomposing at different times.”
The behavioral habits and feeding habits of juvenile catfish, such as schooling together to feed at night, also exposed them to the bacteria, Skeggs said.
“There’s so many elements of natural systems that you can’t always say ‘this is the exact answer,’” Skeggs said. “As natural systems move and things die off, many things came together that made it really a bad couple of weeks to be a catfish in the Ottawa River.”
“And we haven’t ruled out that it could happen again.”
Unlike our carp kill, Skeggs said the natural movement of the Ottawa River helped the speedy replenishment of the water.
“One of the things that made it easy on people was that we have a river, as opposed to a lake, so it tends to clean itself up,” Skeggs said. “It was on a fairly long stretch of the Ottawa river, which is a big, wide, steadily moving river system.”
Jim Buttle, Trent University professor and ground water specialist, agreed that Ottawa likely had it slightly easier because their fish kill happened on a river.
“The lakes will take a long time, perhaps several years, to replace the water that is sitting in the lakes,” Buttle said. “With rivers, the replacement time is much shorter, literally a matter of days or weeks.”
At the time in Ottawa, the Renfrew Country District Health Unit advised residents to avoid using the water or swimming in affected areas.
“The Ministry of Environment did water sampling tests on the water,” Skeggs said. “We did not get any reports of any impact on people related to water quality.”
It wasn’t until Aug. 14, more than 10 days after the kill started, that the ministry did water quality tests on the river, according to a fish kill report evaluation by Meredith Brown of the environmental group Ottawa Riverkeeper.Currently, fish sample tests are still being conducted at Guelph University to determine the primary cause of the death of the carp in the Kawartha Lakes.
The columnare bacteria identified on the fish samples is secondary to a still-unknown primary bacteria, said Scott Watson, provincial fish culture policy and program co-ordinator with the Ministry of Natural Resources in Peterborough.
In Ottawa, Skeggs said it was concluded that no other bacteria was found to have killed the catfish.
“We did not find any other bacteria on the fish that could have been considered a primary cause of the fish kill,” he said.
Straight to the source…The Peterborough Examiner