Stoneflies & Mayfilies - Canaries of Our Streams

[fishteck]

This is an interesting articles that should prompt discussion from Bow River anglers. Since Calgary's Bonnybrook Waste Water Treatment Plant has been upgraded we have seen increases in stoneflies in the river. Two species in particular are now important food source for trout, the July Nocturnal Yellow Stone fly and an increasing presence of Skwala Stone fly in May.
At the same time we are seeing a substantial decrease in caddis and the historically important Pale Morning Dun hatch.

Although it is unlikely that water and waste-water management can be changed to increase invertebrate population to enhance trout feed, there is a place for a better understanding of the Bow River bug life.

Mayflies and stone flies are extremely vulnerable to water pollution, which has implications for the larger food chain.

 

 

THECONVERSATION.COM

 

Stoneflies and mayflies, canaries of our streams

Mayflies and stone flies are extremely vulnerable to water pollution, which has implications for the larger food chain.

[FishnChips]

Fishtek, 

   Another informative link, thank you. 
   I mostly fish the Upper Bow, and The Highwood, they are close to home. Retiring has allowed me to explore my home waters to a degree I never could before. I haven’t seen a stonefly during the summers of 2018 or 2019 on my home waters. Not one. I normally see them this area in early June to mid-July over the past 15 years.
   I do not have a huge interest in entomology, and identifying mayflies is challenging because I can’t always catch one.  (I use my hat, sometimes I get lucky and one just lands on me, that is best). The fine details are hard to catalogue. The dark ones look just like the picture above, especially those random dark patches on otherwise clear wings. The late summer and fall Green Drake hatch was invisible to me during summer/fall 2019. I did not see any. Very few dark Mayflies all season. Lots of small pale and yellow sometimes with a greenish tinge. (Yellow Sallies I believe). I did not see any caddies. Dry fly action was slow and I was working on improving nymphing skills so the two dovetailed nicely and I noticed my catch rate from my diary stayed constant by going deeper with nymphing.
   Banff and Canmore both have state of the art sewage treatment plants. Since the last major upgrade a couple of decades ago, the fishing dropped off noticeably in my direct experience in this area and this is supported anecdotally by fishing acquaintances, guides and a locally raised conservation person who now lives and works in BC. 
   This has left me with the perplexing conclusion that some kinds of effluent from sewage plants were good for the bugs and the fish. Is that the same as being good for the water itself? Or humans? Since the “clean up”, bugs and fish have declined. Is the water better? 
   I am still mulling over which changes I am going to make for this coming season (20/21). We have a problem and I will be part of the solution. One thing I am considering is only fishing stocked waters period. I will give the wild fish (the naturals, the wilds and exotics) a break. 

 

[monger]

Nitrogen and phosphorus from waste water fertilizes the river to increase plant biomass and subsequently the bugs. These inputs have been decreasing with more sophisticated sewage treatment. The giant weed mats of the old days left the evening skies clouded with caddis. I miss those days.

Parking lot runoff and pharmaceuticals are having much different effects.

The big flood we had blew a bunch a bugs out to Sask. The result of the flood really changed the available habitats left for the bugs to select as optimal. I think the change in the substrates has changed the bug populations. In many areas there is a lot more sediment.  This is really noticeable below the Highwood where there is a lot more long stretches of flat water

[fishteck]

As always, interesting comments. The Bow River will never return to the "good old day" of high biomass that was continued to be replenished by wastewater treatment outflow. And the trout population has dropped accordingly downstream of Calgary, to what it is now at probably less than 25% of 2000 levels.

FishnChips - what you have seen in Banff and Canmore 20 years ago we are now seeing in Calgary, just a few years later. And Monger, the 2013 flood changed the hydrology of the Bow River, especially downstream of the Highwood where to peak flow during the flood was almost twice what it was in Calgary. There was talk a few years back that there was enough biomass in the Bow River to last for 100 years even if the outflow from wastewater treatment plants was zero. Interesting enough, AEP does monitor the Bow River water quality routinely and although quality has improved by the data they record it appears to not have improved as much as one would expect. Although I have not checked the information in the past couple of years.

I had the opportunity to look at some raw data from an invertebrate survey on the Bow River in 2014 and compared it to a previous report from 2009 to see if there was a change in the mix of the invertebrates in the river pre- and post-flood.  The sampling was in fall of both studies principally due to river bed access during low flow season and only once in the year. The analysis I did told us very little, except that mayflies predominated across both studies. I was surprised that the stonefly nymph numbers were so low considering the higher presence of golden stone in recent years. The AEP specialist in this area  pointed out that seasonal changes, the environment and life cycles all play a role and will impact a single sampling far more than species differences.

There is a place to do some more investigation here and it would give a better understanding of what is changing to fish feed source. But its strictly an academic question since it is unlikely that water and wastewater management will change to improve the fishery!

[DonAndersen]

Fished the Crow from 1980>2002. Each time more sewage was directed to the Frank plant, the lower the insect population. The last straw was the East Hillcrest flow to Frank Slide plant reduced catch rate  to abysmal. 
Further, the fish health dropped obviously effecting spawning success. 
All pollution is not bad.

Don

[Castuserraticus]

On 2/4/2020 at 2:48 PM, monger said:

Nitrogen and phosphorus from waste water fertilizes the river to increase plant biomass and subsequently the bugs. These inputs have been decreasing with more sophisticated sewage treatment. The giant weed mats of the old days left the evening skies clouded with caddis. I miss those days.

Parking lot runoff and pharmaceuticals are having much different effects.

The big flood we had blew a bunch a bugs out to Sask. The result of the flood really changed the available habitats left for the bugs to select as optimal. I think the change in the substrates has changed the bug populations. In many areas there is a lot more sediment.  This is really noticeable below the Highwood where there is a lot more long stretches of flat water

The main change to the river from the flood was loss of mobile, midstream gravel bars. The high flow carried the gravel down to manmade collection points (flow restriction) above the weirs. Since the Bow is entirely dam controlled, no new gravel can enter the system from upstream to replenish the bars. The only source of gravel, other than the Highwood, is cannibalizing the banks. The river is permanently wider and shallower with a fixed, boulder streambed instead of a mobile gravel bed. This could result in more mud deposited in some areas.Bug habitat changed.

[monger]

Unstable banks that lost all their root protection continue to add fine sediments. This is going to be a problem for quite some time.

Hopefully the rainbows can find enough food/change their hunting practices to put some more weight on. They are still quite thin compared to what used to be normal

[SilverDoctor]

6 hours ago, Castuserraticus said:

The main change to the river from the flood was loss of mobile, midstream gravel bars. The high flow carried the gravel down to manmade collection points (flow restriction) above the weirs. Since the Bow is entirely dam controlled, no new gravel can enter the system from upstream to replenish the bars. The only source of gravel, other than the Highwood, is cannibalizing the banks. The river is permanently wider and shallower with a fixed, boulder streambed instead of a mobile gravel bed. This could result in more mud deposited in some areas.Bug habitat changed.

Perfect point, there is a real problem now the above mentioned gravel bars no longer exist. Much of that mid-river and in the past banks, these where at one time spawning areas. Now no new gravel but the silt abounds and in some places is really becoming deep.

[fishteck]

I don't buy the argument that a single flood, that is the 2103 flood is a principal reason for the drop in bug life because of a change in rock deposits and sediment. We have seen floods ever since trout were put in the river. Admitting they were of less magnitude in the past than in 2013, but severe enough to change the contour of the river bed.  We tend to focus on the Bow River flows through Calgary, but as I have stated before, the flows below the Highwood were almost twice what they were above during the 2013 flood and therefore the impact of high flows would have been higher on the lower stretch of the Bow River.

Hydro dams have been sited in many publications for the demise of invertebrate life and most frequently a shift in the proportions of mayflies, stoneflies and caddis flies. Therefore we should expect to see a drop in caddis flies and an increase in mayflies with a redefined flush each spring runoff. This has now been in place since the modified operations of the upstream hydro dam system to meet the need for flood protection for Calgary. Each April/May Ghost Reservoir is dumped followed by natural flushes through to the first week in July. This should assist with the recruitment of mayfly and stoneflies with a demise of caddis flies. Add the upgrade of wastewater treatment plants in recent years resulting in decreased biomass in the river, with less weeds and invertebrate life, we can expect to see declining fish condition and most likely a continued decline in trout numbers.  

[monger]

The influence of chemicals we are adding to the environment is no doubt having a significant effect. Ever-growing City/road runoff, herbicides/insecticides and the vast increase in pharmaceuticals excreted down the toilet are probably all adding to the problem. A complex issue indeed.

[fishteck]

Monger:

Although you are correct that chemicals, run-off, pesticides and pharmaceuticals may have an effect on both invertebrates and fish, the questions is just how much impact and is there a reasonable cost effective way to reduce concentration discharged into the river is the question. It is being surveyed and reports if not available will be available sooner than later. Its basically an academic question, but will little or no way of resolving the issue if the human race is to survive in our current culture.

Bow River Phosphorus Control Alliance

Bow River Phosphorus Plan