The Athabasca Rainbow Trout Is in Trouble

© Scott & Jill Tansowny

We live in a wonderful province filled with biodiversity and amazing species of plants and animals. One of these amazing animals is the Athabasca rainbow trout. It is a fascinating fish but it is in trouble. What can we do to save this amazing fish?

What Are They?

The rainbow trout is a coldwater salmonid native to the Pacific coastal areas of northeastern Asia and North America from Alaska all the way down to northern Mexico.¹ This trout is native to Alberta in the Athabasca River drainage and is present throughout the Athabasca drainage in the cool, clear, high elevation streams; typically in 3rd and 4th order streams where water temperatures remain cooler and oxygen levels remain higher throughout the summer.²

What Makes Them Unique?

Rainbow trout are a beautiful fish with long, slender bodies, silver sides, black spots, and a pink line along their body. The Athabasca rainbow trout is very similar to other rainbow trout with a few differences due to the adaptations they have developed living in small, cold, and unproductive streams.

The Athabasca strain spawn later in the spring, have a slower growth rate, and reach a smaller size at maturity.³ As well, they keep 8 – 12 parr marks (oval-shaped dark marks) throughout their lives unlike other rainbow trout that lose these markings as they mature. The small size is thought to help them adapt to their extreme cold environment and the parr marks are suspected to help camouflage the fish from predation in the small, clear streams they inhabit.

Interestingly, there is anecdotal evidence that these are not adaptations but are actually just the result of living in extreme conditions. Fish have been put in more productive, less harsh water and have been found to grow at a much faster rate and lose their parr marks.

The rainbow trout found in the Athabasca watershed are a distinct ecotype, unique to Alberta. These salmonids are found nowhere else in the world.

How Did They Get Here?

There is some debate as to how the rainbow trout got into the Athabasca. Behnke theorized that the Athabasca strain rainbow trout made their way into the watershed 12 000 years ago when a rainbow trout subspecies, the redband trout, made its way from the Columbia River to the Fraser River, and then into the Laird, Mackenzie, and Athabasca Rivers.⁴ This would have occurred as glaciers retreated exposing new land and creating large lakes and rivers to be populated by new flora and fauna.

A study in 1994 by Carl, Hunt, and Ihssen disagreed with this theory when they found a population of trout in the Athabasca watershed — from Wampus Creek — that had genes very different from trout in the Fraser River. They claimed that these trout must have been present in the Athabasca watershed before the glaciation, meaning that they would have been here for at least 65 000 years.⁵

DNA studies of trout from the Athabasca drainage in 2000⁶ and 2007⁷, however, backed up Behnke by finding that trout from Columbia River did in fact have very similar genetics to the Athabasca trout. However the trout got here, evidence is overwhelming that they are in fact native to this watershed and are a unique ecotype adapted to the specific habitat found in the Athabasca River watershed.

Athabasca Rainbow Trout: Endangered?

The status of the Athabasca rainbow trout is currently endangered according to the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). A 2014 study by COSEWIC estimated that by the year 2039 (15 years or 3 generations of Athabasca rainbow trout), the fishes’ population will decline by more than 90% from current numbers. This qualifies this fish as endangered, one step away from the Athabasca ecotype being extinct. The main driving force for this prediction is the loss of suitable habitat due to the building of roads, coal extraction, oil & gas extraction, forestry, and agricultural practises. Global warming; competition from introduced, invasive brook trout; and hybridization with stocked rainbow trout are also factors.⁸

The Athabasca rainbow trout has not yet been added to Canada’s Species at Risk Act by the Minister of Environment, however. This means that no action plan is required to be put in place by the federal government.

Alberta’s Recovery Plan

In 2014, Alberta made a five year recovery plan for the Athabasca rainbow trout.⁹ This plan includes investigating and monitoring basically every negative factor to the populations of the trout. Unfortunately the plan is littered with words like 'review', 'identify', 'promote', and 'consider', instead of concrete steps with deadlines and values. The problems are laid out including everything found by the COSEWIC report as well as a few other factors such as irresponsible OHV being linked to the habitat degradation.¹⁰ The issue is clearly laid out but a finite, measurable plan on addressing it is not.

What Are the Threats?

Habitat

As mentioned in every report I could find, habitat destruction is the biggest threat to these fish. Logging creates extra water discharge to creeks, increasing both silt in the water and the temperature of the creek, making the habitat less suitable.¹¹

Roads introduced for logging and for resource extraction act in a similar way, causing water to flow through ditches and into the creeks once again causing extra siltation and changing water temperature. As well, the erection of bridges and creation of culverts impacts the fishes’ spawning and winter survival through increasing water velocity and creating an impassable barrier to the fish.¹²

Another threat to habitat is OHV use. As OHVs cross creeks they add to the sediment in the creek adversly affecting the suitability of the streambed to egg laying. As well, OHVs can directly destroy the redds of the trout jeopardizing the chances of the affected fish having offspring.¹³

Non-Native Salmonids

Introduced rainbow trout are another factor that is highlighted in the government reports due to hybridization reducing the populations of the pure strains of the Athabasca ecotype. This is challenged, however, by Taylor, Tamkee, Sterling, and Hughson where they found in their genetic study, “except in a few localities .. little to no influence of past stocking of hatchery rainbow trout on the genetic diversity or structure of native populations.”¹⁴ They hypothesized that this is partly due to the tough conditions that hatchery trout are not as well adapted to as the native strain.

The other non-native salmonid that is impacting the rainbows is introduced brook trout. Brook trout compete with rainbow trout for both food and habitat. It is not clearly understood, however, whether this is a cause in the decline of the rainbow trout or if the success of the brook trout is a result of the rainbow trout declines. As habitat degrades, the brook trout will continue to thrive and possibly supplant the rainbow trout as their quick growth and fall spawning (when less silt is present in the stream) will be better suited to survival in these conditions.¹⁵

Whirling Disease

Whirling disease is a new threat that is working its way up to the Athabasca drainage. Alberta Environment and Parks has confirmed whirling disease in all river drainages in Alberta except the Athabasca and Peace. The Athabasca River watershed is still testing negative but is in the buffer zone. Whirling disease is a parasite that infects salmonids such as trout, char, and whitefish. Rainbow trout, in particular, seem to be especially susceptible to the parasite but so far the Athabasca strain have not come into contact with it. The parasite infects tubifex worms that then come into contact with the fish. In one study, rainbow trout populations were decimated by more that 90% in less than 20 years due to this disease.¹⁶

Climate Change

A last threat to these fish is climate change. Already, climate change has increased global temperatures but how will this impact our rainbow trout? There are three ways that climate change can upset the delicate balance that Athabasca rainbow trout have. One is increased water temperature. Athabasca rainbow trout need water temperatures from 7°C – 18°C to ensure they have the right amount of dissolved oxygen in the water. Another is changes in water levels and flooding due to changes in precipitation. A third is again the changes in water levels and flooding but because of an increase in melting glaciers throughout the summer.¹⁷ Athabasca rainbow trout are adapted to a very specific habitat and large changes in water flows or temperature can have disastrous consequences.

What Can We Do?

This all seems pretty daunting but what can each of us do? There are a few simple things that can be done. One is to prevent the spread of whirling disease by making sure to clean all boats and gear completely before moving from one water body to another. Another thing we can do is to be responsible in our use of OHVs. Do not cross streams or enter water bodies and always stay on the trail.

Habitat loss and climate change, however, are bigger problems that don’t have simple solutions. We need to tell our government representatives that these issues are important and that we need to act now. Industry needs to be phased out of these critical areas and we need to make moves towards renewable, green energy. By reducing our impact on the Earth’s climate and by rewilding sensitive areas and then keeping them wild, not only will Athabasca rainbow trout be saved; many other species will be saved as well.

When the Athabasca rainbow trout are gone, they are gone. There is absolutely no chance for them to be reintroduced as there are no other populations of this ecotype anywhere in the world. We have one chance at saving this fish. We cannot squander it.

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1. Nelson, J. S., & Paetz, M. J. (1992). The fishes of Alberta. University of Alberta.

2. Rasmussen, J. B., & Taylor, E. B. (2009). Status of the Athabasca rainbow trout (Oncorhynchus mykiss) in Alberta. Government of Alberta.

3. COSEWIC. 2014. COSEWIC assessment and status report on the Rainbow Trout Oncorhynchus mykiss in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xi + 60 pp. (www.registrelep-sararegistry.gc.ca/default_e.cfm).

4. Behnke, R. J. (1992). Native trout of western North America. American Fisheries Society monograph (USA). no. 6.

5. Carl, L. M., Hunt, C., & Ihssen, P. E. (1994). Rainbow trout of the Athabasca River, Alberta: a unique population. Transactions of the American Fisheries Society, 123(2), 129-140.

6. McCusker, M. R., Parkinson, E., & Taylor, E. B. (2000). Mitochondrial DNA variation in rainbow trout (Oncorhynchus mykiss) across its native range: testing biogeographical hypotheses and their relevance to conservation. Molecular Ecology, 9(12), 2089-2108.

7. Taylor, E. B., Tamkee, P., Sterling, G., & Hughson, W. (2007). Microsatellite DNA analysis of rainbow trout (Oncorhynchus mykiss) from western Alberta, Canada: native status and evolutionary distinctiveness of “Athabasca” rainbow trout. Conservation Genetics, 8(1), 1-15.

8. COSEWIC. 2014. COSEWIC assessment and status report on the Rainbow Trout Oncorhynchus mykiss in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xi + 60 pp. (www.registrelep-sararegistry.gc.ca/default_e.cfm).

9. Alberta Athabasca Rainbow Trout Recovery Team. 2014. Alberta Athabasca Rainbow Trout Recovery Plan, 2014–2019. Alberta Environment and Sustainable Resource Development, Alberta Species at Risk Recovery Plan No. 36. Edmonton, AB. 111pp.

10. Alberta Athabasca Rainbow Trout Recovery Team. 2014. Alberta Athabasca Rainbow Trout Recovery Plan, 2014–2019. Alberta Environment and Sustainable Resource Development, Alberta Species at Risk Recovery Plan No. 36. Edmonton, AB. 111pp.

11. Sterling, G. L. (1993). Fry emergence survival of rainbow trout, Oncorhynchus mykiss (Walbaum), following timber harvest in two foothill streams of west-central Alberta.

12. Furniss, M.J., R.D. Roelofs, and C.S. Yee. 1991. Road Construction and Maintenance. Pp. 297-323 in W.R. Meehan (ed.) Influences of Forest and Range Land Management on Salmonid Fishes and Habitats, American Fisheries Society Special Publication No. 19, Bethesda, Maryland.

13. Alberta Athabasca Rainbow Trout Recovery Team. 2014. Alberta Athabasca Rainbow Trout Recovery Plan, 2014–2019. Alberta Environment and Sustainable Resource Development, Alberta Species at Risk Recovery Plan No. 36. Edmonton, AB. 111pp.

14. Taylor, E. B., Tamkee, P., Sterling, G., & Hughson, W. (2007). Microsatellite DNA analysis of rainbow trout (Oncorhynchus mykiss) from western Alberta, Canada: native status and evolutionary distinctiveness of “Athabasca” rainbow trout. Conservation Genetics, 8(1), 1-15.

15. Alberta Athabasca Rainbow Trout Recovery Team. 2014. Alberta Athabasca Rainbow Trout Recovery Plan, 2014–2019. Alberta Environment and Sustainable Resource Development, Alberta Species at Risk Recovery Plan No. 36. Edmonton, AB. 111pp.

16. Vincent, E. R. (1996). Whirling disease and wild trout. Fisheries, 21(6), 32-33.

17. COSEWIC. 2014. COSEWIC assessment and status report on the Rainbow Trout Oncorhynchus mykiss in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xi + 60 pp. (www.registrelep-sararegistry.gc.ca/default_e.cfm).