As promised, it’s time to deeper look into forestry roads and analyze what the research can tell us about how they impact trout. In the last post I discussed and introduced the ethical dilemma we face as anglers and why we should be concerned about the abundance of roads. (To read PT. I click here). What I did not do, however, is offer any scientific evidence to support my lofty claims; and that is what I will do in this post.
I am aware that most people are not interested in reading academic journals and sifting through research, or do not have access to academic databases. However, it is crucial that the results of such research studies be in the public awareness so we as an angling community have a better awareness of the threats trout face. Others may want to read the study abstract and inspect methodology; therefore, I will provide links to all the studies for those interested, as well as briefly summarize a couple key conclusions.
Click below for my full literature review on the topic:
In compiling this literature review, I found a few studies particularly compelling. That includes a study done by Eric Valdal and Micheal Quinn in 2011 on some of the Cutthroat Trout streams of the Upper Kootenay River. They studied 5 tributary streams and found roads on erodible soils within 100 m of streams to have the strongest correlation to decreased abundance, while other variables including road density, roads within 100 m of stream, and recent logging were also correlated to decreased trout abundance.
What was not correlated to decreased trout abundance was equivalent clear-cut area, and total disturbance from both wildfire and logging.
The key conclusions made by Valdal and Quinn are that the Spatial Distribution of roads and disturbance within a watershed are at least as important as the cumulative clear-cut area when predicting trout abundance, and that logging of non-fish bearing streams can contribute to decreased trout abundance.
Here is a link to the abstract:
Why would that be the case?
Well, studies indicate that one of the results of disturbance (forestry or wildfire) is a temporary increase in stream temperatures and increased fine sediment. The response of Cutthroat Trout to those things may surprise you. Research is starting to suggest that Cutthroat Trout may actually benefit from increased stream temperatures. Some of the first long term studies of watersheds affected by forestry hinted at this; and recent studies have built on the hypothesis. Increased stream temperatures in the spring can lead to higher survival rates of fry due to earlier spring emergence, and it is generally believed that Cutthroat Trout have many adaptions available to negate the effects of decreased spawning habitat (from temporary increases in fine sediment). Therefore it appears the increased survivorship of emergent fry somewhat negates the lowered reproductive rates and in some cases leads to an increase in average fish size.
This was document in Hartman’s study on Carnation Creek from 1972-1985. This was one of the first long term studies of a watershed heavily impacted by forestry. They found an increase in the size of Cutthroat Trout from 1972-1985, while smolt counts showed no clear pattern of change.
Ryan MacDonald found similar results in 2014 when he studied how increased stream temperatures from climate change would impact Bull Trout and Cutthroat Trout on steams in southern AB. Again, he hypothesized Cutthroat Trout would benefit from increasing temperature because of earlier emergence of fry. He also noted a trend of cooling winter temps, as a result of earlier spring freshet. This, he stated posed a risk to Cutthroat as it may limit the amount of pools available for juvenile over-wintering.
Here is a link to the abstract:
Again, there is that theme. Cutthroat Trout can withstand or even benefit from change…. But they need pools!
One of these early studies documented an infilling of pools due to increased coarse sediment, and also found that 84 % of coarse sediment came from 6% of the road length (Clearwater River Study).
A 1998 study done on roaded and un-roaded stream reaches in Idaho found higher pool frequencies on all un-roaded stream reaches in all stream classes, Proceedings from the Forestry-Fish conference in Calgary in 1996 present studies that show a decrease in pool depth and frequency as well well as reduced fish holding capacity due to forestry related erosion.
I could go on and on.
Point being, the scientific evidence that shows that forestry is slowly but surely reducing our streams fish holding capacity is there. Many sources agree that roads are the single biggest contributor to this.
Google Earth Imagery
Somewhere in AB.
An unscathed watershed within a provincial park
What is also clear to me is that something must change if we expect significant improvements in our Cutthroat Trout populations over the next couple of generations.
Roads will still be built; logging and other industry must continue if our economies are to thrive. What is crucially important is that the we deploy the science at our disposal and enforce road building that promotes ecological values; for trout ecosystems that means not building roads within 100 m of streams, not logging non-fish bearing streams, and reducing roads built on erodible soils.
In the meantime, maybe our Fisheries Managers could focus on habitat rehabilitation?
Maybe our provincial and federal governments can work towards creating more permanently protected areas in the form of Provincial and National parks; areas that can forever remain free from the labyrinth of roads, cut blocks, and unnatural linear features that wreak havoc on our wildlife and fish populations, all over our headwaters.
Maybe, instead of shutting down parks and privatizing crown land, we could make conservation, recreation, and wild ecosystems a priority for our future…
Just a thought.
In the next post I will talk about some options for rehabilitation, the ‘smoke-screen’ that is investment in hatchery programs instead of habitat upgrades, as well as how you can get involved. Thanks for reading!