Bow River trout population on a slow decline

[Guest monger]

I was talking with a researcher who has a grad student running through the history of shocking data available for the Bow river. It looks like there is a strong trend showing population numbers are on a steady decline. The 2013 flood only added to the loss of fish.

Do you folks that have fished the river for the last 20+ years feel that you are seeing less fish? I believe there will be another survey done before the winter hits. With this trend getting more recognition from the government, there may be some kind of action taken. For such a valuable resource, there hasn't been much management/research invested into monitoring the Bow.

[Dangus]

Whirling disease?   seems like the right timing to me.  Pressure also steadily increased, while retention remained.

I haven't fished it for 20 years, but I'd imagine with more fish the size was smaller on average?  You can correct me if I'm wrong.

either way, Id take this number and size over a couple inches shorter on average and double the number of fish. 

 

[krk]

Would really love to see some data on this.  A number of people I talk to will suggest the same thing.  Anecdotally I would tend to agree with your friend but my fishing methods have changed to streamers, hoppers, etc which can be much less productive than deep nymphing.  My frustration is the lack of data that is being shared by our fisheries personnel.  We pay for them to manage this fishery, lets see the data.

Ken

[BurningChrome]

3 minutes ago, krk said:

Would really love to see some data on this.

Yeah, without data it doesn't mean much. What's "steady" and how big is the decline year over year? It shouldn't be a surprise to anyone that there was a larger decline after the floods but can the rest be attributed to anything specific?

[Jayhad]

I would think this trend is correct but my feeling is we aren't loosing biomass

[Dangus]

2 hours ago, Jayhad said:

I would think this trend is correct but my feeling is we aren't loosing biomass

In fact, it's tighter than ever.

[bcubed]

Rob, I would feel the same way, but  we're making up for it in size. I think most of the guides would probably tell you the same thing..

id be curious about the strength of the data, cause everything I've heard is that their data collection and design (if using AEP shocking records) isn't great

[fishteck]

There is no doubt that Bow River trout populations are way down from what was seen in the '80 and '90 when there was a fraction of the anglers on the river as compared to what we see today. The habitat and food source has changed dramatically. To say that there is "a steady decline"  is a conservative statement that researchers use in the absence of statistical data analysis!

A few years back those with knowledge of the Bow suggested that there was "100 Years" of biomass in the river and that even with the clean up of Calgary's water treatment plants that trout would continue to prosper. Then came ther 2005 and 2013 floods that cleaned out large stretches of the river. Weed growth is minimal and aquatic species range has changed.

There are encouraging signs that trout populations are on the rebound, especially the number of smaller fish on the lower stretch of the Bow between Mac and Legacy. 

What is needed now is to take pressure off the fishery with a better fish management model. 

[ÜberFly]

19 minutes ago, fishteck said:

 

What is needed now is to take pressure off the fishery with a better fish management model. 

Classified system, maybe!?

[toolman]

 I believe that the Bow river bio mass has been greatly diminished since 2011. I have been collecting, photographing and observing the annual hatches on the river in great detail for the past dozen years. Simply put, my  conclusion is there are a lot less aquatic invertebrates in the river and many species have all but completely disappeared.

River angling closures or reducing fishing pressure will not solve this issue. The assumption that fishing pressure is mainly responsible for the trout population decline is misguided and speculative at best.

[trailhead]

Think that the upgrades to the sewage treatment plants on the Bow might have something to do with all of this too?

[toolman]

I think there are likely many contributing factors and events such as the extended high flows of turbid water releasd in 2011 from a malfunction at one of the upstream power generators, which coated the stream bottom with fine clay from the high Alpine. These turbid flows which lasted through the summer into late autumn, reduced  sunlight penetration down to the stream bed where aquatic vegetation and moss's grow. (The Sapro outbreak followed soon after). That year, I noticed a major reduction in many species of common Mayflies.

The downward trend of aquatic invertebrates continues to this day, with many species of stoneflies, water boatman,  back swimmers, fall caddis greatly reduced or virtually eliminated.

Then came the flood of the century in 2013 which certainly had a huge impact on biomass loss and habitat. 

As for the water treatment upgrades, it has most likely had an impact on biomass reduction. 

The numbers of fish we now have is simply what the habitat can support.  Rivers are living, dynamic systems that are constantly changing.

The fish are healthy and not showing signs of major stress and disease, so maybe their numbers will rebound when conditions allow.   

[fishteck]

Toolman:

If there is a loss of habitat and food source due to whatever events have taken place, then as you say, the population of trout that the river can sustain has probably reached a low threshold.

Hopefully that is not the case and we will see the current numbers of young trout survive, grow and reach the mature size that we have seen over the past 2 years.

 

 

 

[toolman]

Yes, I hope so as well.         .