Bull trout in Cultus Creek, Darkwoods, BC (Photo by Bruce Kirkby)

Bull trout in Cultus Creek, Darkwoods, BC (Photo by Bruce Kirkby)

Looking out for bull trout

Bull trout in Cultus Creek, Darkwoods, BC (Photo by Bruce Kirkby)

Bull trout in Cultus Creek, Darkwoods, BC (Photo by Bruce Kirkby)

Bull trout are great lovers of cold, clear, mountain and coastal rivers throughout northwest North America. In British Columbia, the formerly healthy populations are believed to be in decline, earning them the status of being "blue-listed" by the BC Conservation Data Centre.

The long, slim, recreationally popular fish is found in abundance on Darkwoods, where fisheries biologists have recently spent time monitoring their populations as part of a broader study to determine bull trout population health in the Kootenay region.

Steve Arndt is the biologist who heads up this study, which is an initiative of the Fish and Wildlife Compensation Program. Steve spoke to the Nature Conservancy of Canada (NCC) about the project and the fish that is earning so much attention.

Steve Arndt, fisheries biologist (Photo by Janice Arndt)

Steve Arndt, fisheries biologist (Photo by Janice Arndt)

Tell us a bit about bull trout. What are they like?

SA: Bull trout are part of a group of fish that include dolly varden and arctic char. They are very attractive, especially during spawning, when the males sport a brilliant red on their fins and belly, which is touched off with black and white trim. Adult bull trout in lakes typically feed on smaller fish, and where there is abundant food they can grow to over 20 pounds (10 kilograms).

All bull trout need streams with cold, clean water for spawning and juvenile rearing. Some populations above waterfall barriers live their whole lives in the streams, but most migrate downstream into a larger river or lake to grow and mature.

They’re an important species to research because they are vulnerable to habitat degradation and have declined in some areas, especially south of the Canada-U.S. border. In addition, they are the most abundant top predator in our large lakes — a key component of the ecosystem, and a very popular species in the recreational fishery.

How did you get involved in studying bull trout?

SA: I first got involved in studying bull trout as part of a monitoring program to evaluate the success of a hatchery that was operated on the Arrow Lakes. Eventually the hatchery was closed due to poor survival of the stocked fish. After the hatchery closure, we began to assess the sources of natural reproduction and develop methods for monitoring population trends, initially in Arrow and then in Kootenay Lake.

Why is this project necessary?

SA: The Fish and Wildlife Compensation Program funds two major compensation projects on Kootenay Lake: a large-scale nutrient restoration program, and the Meadow Creek spawning channel. We hope to restore bull trout and Gerrard rainbow trout populations by enhancing their primary food source, kokanee.

How is the research conducted in the field?

Bull trout faces an upstream barrier on Cultus Creek, Darkwoods, BC (Photo by Bruce Kirkby)

Bull trout faces an upstream barrier on Cultus Creek, Darkwoods, BC (Photo by Bruce Kirkby)

SA: First we did reconnaissance surveys by foot and helicopter, looking for waterfalls or other obstructions that would be a complete barrier to any bull trout migrating upstream. Then in late September and early October, after the bull trout had completed spawning, two observers wearing polarized sunglasses walked from the barrier downstream counting the number of bull trout redds in each stream. Redds are excavations where eggs are deposited to incubate over the winter and look like dish-shaped depressions in the stream bed, with a deposit of cleaned gravel. 

In Kootenay Lake many of the spawning streams are in remote areas without road access, so in some cases the crews were dropped off by helicopter (with camping equipment) to hike downstream through some very challenging terrain. It was quite an adventurous trip into beautiful, seldom-traversed country.

The work on Kootenay Lake tributaries was conducted for the FWCP by a local firm, Redfish Consulting, with help from staff of the Ministry of Forests, Lands and Natural Resource Operations. 

What threatens the bull trout population in the Kootenay region?

SA: The most significant threat to bull trout in my view is habitat loss. These fish need cold, pristine streams. Anything that reduces water quantity or increases water temperature in streams is likely to reduce populations.

Another factor for some specific populations is competition with introduced species (for example, eastern brook trout). Fishing has the potential to significantly reduce populations, but this impact can be controlled with fishing limits and seasons.

What do you hope to achieve through this research project? What would be the best outcome from these efforts?

SA: This is the first ever measure of bull trout abundance in Kootenay Lake tributaries, and is important to show us that the current lake population is robust. If repeated every two to three years over the long term, this survey will provide a valuable index for detecting population changes, and an important performance measure for evaluating the benefits of the FWCP nutrient and spawning channel projects.

Ultimately this research can help us better tailor conservation activities to maximize ecological and angling benefits. It should also lead to better protection of the key stream habitats since these important spawning and rearing areas will be documented. Three of the streams in the survey are located in or adjacent to the Darkwoods property and are now known to be very important habitats to the bull trout population of Kootenay Lake.


The Fish and Wildlife Compensation Program (FWCP) is a joint initiative of BC Hydro, the provincial government and Fisheries & Oceans Canada to conserve and enhance fish and wildlife populations affected by the construction of BC Hydro dams in the Columbia Basin.

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