Banff Park Fish Kill Continues

[McLeod]

Parks wants to restore lakes to natural state

 

By Cathy Ellis - Rocky Mountain Outlook

 

Parks Canada is considering two options to kill non-native fish in remote alpine lakes in Banff National Park, including the use of poison or temporarily damming

 

the lakes to return waters to their natural state.

 

The plan is a last-ditch effort in a long-term ecological restoration project aimed at returning Devon Lakes to a pristine state and protecting the health of threatened bull trout downstream in the Clearwater River.

 

Devon Lakes is a series of four alpine lakes that form the source of the Clearwater system in the front ranges of Banff National Park. The lakes were never historically home to fish, but non-native brook trout were introduced into the lower and middle lakes in the 1960s for sport fishing.

 

Despite huge efforts over the past five years, and the fact that only one fish was caught last year, Parks Canada officials say they are not convinced they have captured all of the non-native brook trout there.

 

“Doing this restoration work allows us to bring a system back to the fishless water that it was previous to stocking,” said Charlie Pacas, Parks Canada’s aquatics specialist in Banff National Park.

 

“We haven’t chosen one method over the other yet, but will do so as an evaluation of costs for the proposals is refined and the discussions and thinking on the environmental assessment proceeds.”

 

One option is to use rotenone, which is an odorless chemical that occurs naturally in the roots and stems of several plants and is poisonous to fish. The other option is what is known as de-watering, which entails closing off the flow from the headwater lakes into the Clearwater River.

 

Basically, it involves damming the upper and middle lakes, which would result in little flows into the Clearwater. Reduced flows would then concentrate the fish into smaller areas, most likely pools in the Clearwater. Then the fish would be removed by electro-fishing or piscicide.

 

An environmental assessment is required before the project can move ahead.

 

Brook trout have escaped from these two lakes into the main tributaries of the Clearwater River, which is a serious concern because they are known to out-compete, displace and crossbreed with threatened native bull populations.

 

But the Upper Devon Lake, isolated from the other two lakes by a series of impassable waterfalls, was never stocked with fish and is serving as an ecological benchmark for the restoration project.

 

For the past five years, Parks Canada has been working to try to remove all of the fish in the upper and lower lakes. Gillnetting in both lakes appears to be very successful. So far, there have been about 28,000 net nights of gill nets without fish.

 

On the other hand, stream electro-fishing over the past five years has reduced brook trout capture to near zero levels, with 10 brookies caught in 2007. However, one fish was caught in 2008.

 

No young-of-year have been captured since 2005.

 

But despite their huge multi-year efforts, Parks staff have still failed to eliminate all brook trout.

 

Parks Canada says it will take several more years to do so if they don’t resort to poison or de-watering.

 

“We would have hoped for zero fish in electro-fishing last year, but we got one, and that suggests to us there’s more than likely one in the system. I think there’s too many hiding spots for these guys,” said Pacas.

 

“What could end up happening over time is the fish will start moving through the system if we haven’t got every last one, and eventually you’ll get a male and female that will find one another,” he said.

 

“If mating is successful, it basically starts the thing of more brook trout in the system and, given the level of effort we’ve put in, we’d like to eliminate rather than let them propagate again.”

 

Throughout this project, Parks called on the expertise of several leaders in their field, including Canadian aquatic experts David Schindler and Brian Parker, along with American Brian Finlayson, considered an expert in the area of fish poison.

 

The experts say rotenone has widely proven its value as a fish eradication tool, given it is highly effective at removing fish, yet it is not a persistent poison.

 

On the downside, they noted rotenone would likely kill invertebrates in the lakes and streams that are treated with the poison. But, the experts said, experience in Jasper National Park shows invertebrates will recover within two to three years.

 

Pacas said invertebrates were collected from five sites in July, August and September of last year in preparation for the possibility of a piscicide application at Devon Lakes this year.

 

Pacas said the timing for the project is in late summer or early fall, when water levels entering the streams are low and there is little melt coming off the glaciers.

 

“My preference would be to dewater before a piscicide application, as this would reduce the stress to the invertebrate community and would mitigate the public concerns of using a piscicide,” said Pacas. “Dewatering is certainly do-able.”

 

Pacas said based on the success of gillnetting in Devon Lakes, having 28,000 net nights without fish, would certainly suggest this technique could be used in other areas for aquatics restoration.

 

“As for electro-fishing, I think we were successful in that there are so few fish left in the system,” he said.

 

“I guess electro-fishing a system to the point of no fish would have been ideal, but that’s rare and I’m not sure anyone’s been able to do it.”

 

Only six lakes within Banff National Park are known to have viable bull trout populations. Of the 19 species of fish found in the national park, only 11 are native to the area.

 

More than 119 lakes in the national park have been stocked with fish at least once over the last century.