Stream Tender Magazine

June 2015 Issue

Removing Stream Blockages to Allow Fish Migration Upstream

    In the spring of 2015, Bow Valley Habitat Development obtained all of the necessary permits and permissions to conduct a beaver dam removal program on the lower reach of Bighill Creek.

    As is always the case, it was easy to find enough volunteers to help achieve this objective. Local fly fisher’s know that by removing old beaver dams and stream blockages will insure that there is free passage for trout to migrate up the system.

    Early season is the best time to complete this task, because trout have a natural tendency to migrate up small streams in the spring of the year, when there are high flow events to help them on their way.

    Usually, right after a freshet or during the melt of spring ice and snow is the perfect time for trout to navigate the waters of small creeks. Instinctively, trout know that the higher flows will allow passage around or over obstacles that would block passage under normal flow levels.

    However, during a dry spring with little run-off or precipitation, the conditions are not suitable for a typical spring  migration. This is where volunteers with waders and a good amount of determination can help out in the situation.

    On one Saturday morning, a group of four volunteers removed four major blockages on the lower reach of the Bighill Creek, in the Town of Cochrane, Alberta. More dams are scheduled to be opened up, in the next month or so on the stream.

Above: The mature willow in the centre of the stream channel in this photo is still alive, so dead woody debris was removed from a blockage that the tree had created, allowing trout migration up past the old willow’s location.

    A funny thing happened on the day of the project that convinced new comer Tim Carlson that the work being done was worth the effort. While working in his chest waders, removing pieces of old branches from around the old mature willow tree pictured above, a small trout went darting upstream past him.

    The trout had being holding just downstream from the blockage, just waiting for the opportunity to scoot up the stream channel when there was an opening.


    The fish swam right under the nose of Tim, while he was bent over pulling limbs from a jam under the old willow tree. It is incidents such as this that can convince a volunteer that their work is doing some real good for the fishery in the creek.

    Bow Valley Habitat Development has permissions from the first three landowners up from the confluence of the creek with the Bow River. By the time that the program is completed, later this spring, trout will have a

route to move freely up the bottom 3 kilometres of the creek.

    Over time, brown trout will eventually have access to the Upper Spring Creek, where they can spawn and recruit new generations of trout into the upper reach of the Bighill Creek. This is one of the primary goals behind the program.

    Presently, only brook trout are spawning in the Upper Spring Creek and historically, brown trout have also utilize the spring creek for reproduction.

Mountain Whitefish Numbers on the Rise

    This spring, while fly fishing on the Bow River in Cochrane, I caught a lot of smaller sized Mountain Whitefish. More so than I have in previous years. This is a good sign of things to come.

    Over the past 10 years or so, I have noticed a sharp decline in whitefish on the Bow here in my home waters and this has puzzled me.

    At one time, back approximately 20 years ago, you could catch plenty of this sport fish on the stretch of the Bow River between the Ghost Reservoir and the Bearspaw Dam.

    Since that time, the Town of Cochrane has changed its effluent treatment system and started to

pipe the untreated sewage into the City of Calgary for treatment, before the water re-enters the Bow River.

    With this loss of nutrient entering the Bow just downstream of the Town of Cochrane, the amount of food for whitefish has declined and thus the numbers of fish. Aquatic invertebrate numbers are reduced when the amount of nutrient declines in the river.

    Further upstream, the Towns of Canmore and Banff have also improved their effluent treatment systems and reduced the amount of  nutrient enrichment into the Bow River. So all of this combined has made the Bow a little cleaner, but less enriched with organic nutrients.

    This change in the balance of nutrient has probably caused an adjustment in whitefish populations.

    Now that the Town of Canmore has more than doubled in population, over the past 10 years, the amount of nutrient in the Bow River has once again increased.

    Despite the very efficient treatment facility in Canmore, the volume of treated water has increase substantially and now the river is getting more productive for both food and fish populations.

    This could explain the sudden increase in whitefish in the Bow downstream. I hope that the trend will also help increase the number of trout that reside in the Bow as well.

    Fortunately, the Town of Cochrane and the City of Calgary, both have very efficient water treatment plants for our drinking water supply, so this is not a concern when it comes to human consumption.

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“ It Should be A Great Year For Spawning Rainbow Trout on the Jumpingpound Creek and Other Area Streams “

    Over the past three months, we haven’t had a significant run-off event on the Jumpingpound Creek this year. If there are no beaver dams to block a migration up the system, we should see a great spawning season for the rainbow trout that both live in the creek and migrate upstream from the Bow River.

    I also suspect that the trout may have started spawning earlier this spring than they normally do, because of the warmer water temperatures in the creek. This means that the rainbow trout eggs have already been incubating in the gravel spawning beds for some time now.

    On a normal year, the eggs usually start to hatch in July and young rainbow trout fry will also start to emerge from the safety of the gravel redds. At this point in time, even if we get a week or more of a lot of rain, resulting in high flows, the trout eggs will probably already be starting to develop into an eyed egg stage.

    Once the eggs are this far advanced, they should be hardy enough to survive being flushed down the system, if a moderate flood does take place. After seeing that some rainbow trout eggs survived the big flood of 2013, I have gained a whole different perspective on how resilient trout eggs can be.

    The same holds true for many of the other rainbow trout spawning streams in our area that are tributaries to the Bow River. Streams on the Highwood Creek system and further south on the Oldman and Crowsnest streams.

    However, I will need to wait and see in the early summer of 2016, when the young of the year (YOY) migrate down in the Bow River in the Town of

Cochrane. This is when the spawning success from the year before can be realized.

    If there was a good hatch the year before, I will usually catch plenty of small rainbow trout in the 4 to 5 inch size range. I often feel guilty about catching such a small trout on my trout flies, but with smaller hooks and a gentle removal of the hook, along with a caring release, will help my conscience.