Species Introduction: Mountain Whitefish

Meet the Mountain Whitefish: a quiet star of our rivers.

The Mountain Whitefish, Prosopium williamsoni

If you spend time around rivers or mountain lakes in western North America, there’s a good chance you’ve been near a Mountain Whitefish—even if you didn’t know it.

They might not be as flashy or well-known as trout or salmon, but Mountain Whitefish play an important role in keeping our freshwater ecosystems healthy.

A juvenile mountain whitefish surveyed by FCC. Photo credit: Matt Wallace

Mountain Whitefish have a sleek, silvery body with a bronze or light brown back. They have a small, toothless mouth tucked under a pointy snout—this type of mouth is called “subterminal”. Other distinguishable characteristics include having large scales.

Their diet mostly consists of the larvae and pupae of small aquatic insects that live on or near river and lake bottoms. Now and then, they’ll grab insects floating near or just under the water’s surface. Whitefish use their fleshy snout to flip rocks and to root around for food tucked away beneath cobbles and gravel. Their torpedo-shaped body and stabilizing fins help them hold steady in fast currents where many other fish would struggle.

Distribution of Mountain Whitefish in Alberta. Image Credit: Nelson and Paetz (1992)

Location and Distribution

These fish are found across western North America. In Alberta, they live in clear, cold mountain streams and lakes.

Some Mountain Whitefish stay in one spot all year, but many move between different areas depending on the season. They usually have separate spots for:

• Feeding in the spring and summer

• Spawning (laying eggs) in the fall

• Overwintering during the cold winter months

Spawning

Traditionally occurs between late September and November. During this time, groups of Mountain Whitefish move into shallower parts of lakes or streams. Unlike trout, they don’t dig nests (redds) for their eggs. Instead, they scatter them over gravel, and the eggs stay there through the winter. Over the winter, they develop and eventually hatch around March!

What makes them important?

Mountain Whitefish are known as an indicator species. That means their presence can tell us about the health of the ecosystem. Because they live in so many different freshwater environments and have relatively stable populations, scientists use them to monitor environmental changes. In short, if Mountain Whitefish are thriving, it’s a good sign the rest of the ecosystem is doing well, too.

Bull Trout: Predators of Mountain Whitefish. Photo Credit: Adam Peters

These fish are also an important food source for Bull Trout, one of Alberta's native trout species. As Bull Trout are classified as Threatened in Alberta, it’s crucial that we protect and conserve the ecosystems that both of these fish live in.

So, while they may not be the most famous fish in the water, Mountain Whitefish definitely deserve some attention. They're an important part of our natural world and a reminder of how all species—big or small—play a role in keeping ecosystems balanced.

References

Kranzfelder, P., Anderson, A.M., Egan, A.T., Mazack, J.E., Bouchard, J., Rufer, M.M.,  Ferrington, J. 2015.

Use of chironomidae (Diptera) surface-floating pupal exuviae as a rapid bioassessment protocol for water bodies. JoVE. 101: e52558–e52558.

Nelson, J.S., Paetz, M.J. 1992. The fishes of Alberta. 2nd ed. University of Alberta Press. 248-252.

Popowich, R.C. 2005. Determining Bull Trout habitat and prey selection using snorkel surveys and stable

isotope analysis. M.Sc. Thesis, University of Edmonton, Edmonton, AB. 62.

Siddig, A.A.H., Ellison, A.M., Ochs, A., Villar-Leeman, C., Lau, M.K. 2016. How do ecologists select and

use indicator species to monitor ecological change? Insights from 14 years of publication in Ecological Indicators. Ecol. Indic. 60: 223-230.