Invasion in the Crowsnest River
There is a nasty little creature lurking in the Crowsnest River these days. It is a particularly insidious microscopic parasite of the myxosporea family known as “Myxobolus Cerebralis” (Mc). When I first read that name I thought to myself. Oh Oh! Any name that has cerebral in it can’t be good.
And it isn’t. The disease caused by the parasite is known as whirling disease and its presence was verified back in 2016 when testing revealed 100% of fish samples in the lower part of the Crowsnest River tested positive for Mc. This is a blight that has led to major trout declines in Colorado and Montana.
The executive summary of a 2019 Alberta Government technical report entitled: “Status of whirling disease in the Crowsnest River”, indicates that by 2018, “clinical signs of the disease were present in Rainbow Trout and Mountain Whitefish, while yearling Rainbow Trout appeared to be largely absent in the lower Crowsnest River.”
This 2018 discovery prompted the comprehensive investigation of 2019. The study’s mandate was to monitor each segment of the Mc life cycle and document its impacts as six sites along the Crowsnest River. There was some pretty serious and comprehensive science that went down that year at these sites. If you are interested in the 40-page document and its methodology you can go to https://open.alberta.ca/publications/9781460148402 to view the technical report.
The six sites were downstream of Crowsnest Lake, up and downstream of Frank Lake, downstream of Byron Creek and up and downstream of Lundbreck Falls, which is a natural fish barrier. There was also a sample site on the Oldman River near the bridge over Highway 22. I will explain briefly what was done at the sites but first you need to know, if you don’t already, how it all goes down with the disease.
Whirling disease attacks salmonid fish (salmon, trout and whitefish) and has what they call a complex two-host cycle. It alternates between an aquatic worm host called Tubifex tubifex and a salmonid host. The parasite moves between these hosts by two infectious spore stages. I hate that word spore. It connotes something nasty even by its sound.
The parasite passes between hosts through its infectious spore stages. The myxospores can be shed into the water by either dead or living fish hosts. Tubifex worms consume the spores in the sediment or by eating fish carcasses. In the worm the parasite develops into what they call the TAM stage (triactinommyxon) which takes about three or four months. They then get released by the worm and because they are semi-buoyant, float in the river and attach to the fins, gills and skin of fish. Nasty business this. They inject their sporoplasm (see Aliens Part Three) into the fish and thus begins the myxospore development again.
Somewhat like that creature in Aliens, the myxospore goes after and feeds on the cartilaginous tissue of the fish and matures in about three or four months. They are especially hard on what the report calls YOY(young-of-the-year) rainbows. Clinical signs are spinal deformities or a bent tail, black pigmentation, the gill cover appears frayed and shorter, and there are cranial deformities like distorted jaw and other cranial abnormalities like bulging eyeballs and a shortened snout. All in all a disturbing development.
The study at the six sites used several processes for assessment including water filtration sampling to calculate the number of TAM’s (floating spores) per liter. There was worm community assessment where they selected ideal worm spots like slow moving or stagnant sections of the river and stirred up a 10 cm depth of sediment to collect and document abundance of worms.
Temperature loggers were also installed at each monitoring site. Incidentally, these sites all had what the report referred to as “sentinel cages.” The temperature, both in the stream and in the cages, was systematically monitored. Sentinel cages were specifically designed using oval stock tanks with wooden tops with locks to prevent vandalism and predation. They were secured in the river at the sites and between 70 and 140 fingerlings were placed in each of the cages. These were 15-week-old unaffected rainbow trout from a trout farm near Red Deer. The tanks were checked and cleaned every two or three days and the fingerlings were fed dry feed. This was referred to as Phase One- Infection Prevalence
After this study was complete there was a Phase Two using the same cages that focused on fish survival with an interesting twist. Once Phase One fingerlings were removed, a new batch of 23-day-old fry specifically bred from milt and eggs from Lyon Creek were inserted into the tanks and again monitored and collected systematically for testing. Following all this a fish sampling program was conducted (backpack electrofishing survey) to assess clinical signs of whirling in wild caught fish. All surveys were within 500 m of each sentinel cage site.
A lot of serious professional scientific assessment went into this study and it indicates an emerging threat of whirling disease in the Crowsnest River. Lots of important recommendations within the report and Alberta Environment and Parks are currently working on viable options to help maintain the Crow as a healthy sport fishery.
So why, you ask, did you get involved in this issue? I was in fact invited by on June 19th by Monica Bartha to come to Burmis Lake to meet a team of Trout Unlimited (TU) volunteers. Monica joined the Oldman River Chapter of Trout Unlimited in 2019 and is now director of TU’s leases at Burmis Lake and Hillcrest (downstream of the west Hillcrest Bridge).
The Oldman River Chapter is heavily supported by the Lethbridge community and that day they were out in force at the lake. They were there to install a whirling disease decontamination station for fisherman that park at the lake and walk down a path to the river. The station has two benches, an interpretive sign, a special foot brush and a boot-cleaning tool installed there. The sign gives specifics about cleaning mud or sediment out of wader boots and equipment and ensuring that no water is retained in any equipment such as watercraft or containers. It also indicates one should make sure one’s waders are completely dry before fishing another body.
The 2019 study revealed that nearby rivers such as the Carbondale and Castle tested negative (so far) so fisherman moving from the Crowsnest to another river can potentially transport spores there if they are not mindful.
The Oldman River Chapter is looking for volunteers to join them as they work, as all TU’s do, at conserving, protecting and restoring Canada’s freshwater ecosystems . No qualifications or experience is necessary , just come out as a passionate person who is interested and willing to give a helping hand. TU is just presently wrapping up Redds surveys (fish nests in the gravel of the river).
The chapter is planning some bioengineering/restoration work, a casino fundraiser this summer, and fish rescue in the late summer/early fall. TU member Kelly Riehl , President of the Lethbridge chapter, shared his thoughts that, perhaps new anglers, like new hunters, should take a course prior to being issued their anglers license. All anglers need to be cognizant of where they go, what harm may be done when removing a hook from a fish handling and releasing a caught fish.
The 2019 report concludes that, “anyone using the watershed for recreation can do their part to mitigate and reduce the spread by following the provincial recommendations to clean, drain and dry all gear that is exposed to water and sediment, never move live or dead fish or fish parts between water bodies, and use fish cleaning stations or put fish parts in garbage. Monica’s last word was this it that it’s a good idea for all Crowsnest River users (anglers, kayakers, stand up paddle boarders, and swimmers) to be aware and prevent its spread.
Author’s Note: Once whirling disease is established in a system there is no treatment to remove the parasite.
Life cycle of parasite Myxobolus cerebralis - Alberta Parks and Environment
Affected fish- black scale, bulging eyes, skeletal deformities, shortened gill cover - Alberta Parks and Environment
Trout Unlimited team at Burmis station - John Kinnear photo.
Life cycle of parasite Myxobolus cerebralis - Alberta Parks and Environment