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Gorgeous gymnast not always welcome in all waters

Al von Finster grew up in Whitehorse. He and his boyhood pals regularly piloted their bikes up to Jackson Lake in pursuit of rainbow trout.

Al von Finster grew up in Whitehorse. He and his boyhood pals regularly piloted their bikes up to Jackson Lake in pursuit of rainbow trout. Neither native to the upper Yukon River basin, or common here, the rainbows were a special treat in an angling world dominated by grayling, lake trout and pike.

Von Finster went on to become a Department of Fisheries biologist. Other species and other biological puzzles demanded his attention through the decades of his official employment, but in 2010 retirement began opening new opportunities. “It gives me time to work on areas of interest, rather than just necessity,” he says now.

Von Finster was freed to devote time and energy to researching an old obsession: rainbow trout. How and when did it arrive up here? How has it fared? What does its northern future look like and how might it presence might affect Yukon fisheries?

The biologist’s fascination with the lovely fish coincided with questions being asked about it by the Yukon Fish and Game Association, of which he is a member. The association approached the Yukon Fish and Wildlife Enhancement Trust, which provided essential funding for a research project directed by von Finster. One result was his paper: “The distribution of Rainbow Trout (Oncorhynchus mykiss) in the Upper Yukon River Basin 2013.”

Von Finster began the research by sifting his memory and reading the literature - popular and academic accounts of trout, angling and of the re-engineering of Yukon streambeds. The rainbow trout has established a place in Yukon history as well as in its geography.

The legendary George Black - a Yukon commissioner and member of Parliament, among other accomplishments - conducted the first-known introduction of rainbows into the territory. Before the Second World War, Black planted 25,000 rainbow eggs in the Klondike River, says von Finster. It appears that the Klondike transplant didn’t take.

We must be careful when judging Black’s efforts, von Finster adds. The trout-egg initiative wasn’t mere recklessness, as we might assume in these days of heightened invasive-species awareness. “I think they were looking to the future,” he says. “They were looking toward a future where there would be rainbow trout to catch.”

The first official stocking of Jackson Lake took place in 1956, while the last was conducted in 1959. These fish did better than the eggs planted in the Klondike, and their descendants are found today in Whitehorse’s Porter Creek, McIntyre Creek and in Croucher Creek. A rainbow had also been captured in Lake Laberge at the mouth of Laurier Creek. These fish are frequently seen among the salmon in the Whitehorse Rapids Fishway viewing window.

Rainbows were stocked in pothole lakes such as Hidden Lakes and watersheds that do not have a surface connection to the Yukon River such as McLean Lakes. These fish cannot enter the Yukon River and pose no threat to native fish.

The Yukon rainbows “are not large fish and almost their entire diet is made up of invertebrates,” says von Finster. They aren’t decimating other game fish species here and they aren’t outcompeting them for food.

Meanwhile, well-established Yukon predators such as the northern pike and burbot help keep rainbow numbers in check.

“Nobody has been able to identify or document any harm that has been caused” by introducing rainbow trout to the Yukon, says von Finster.

In the introduction to his paper he quotes the Yukon government’s definition of invasive species: “An organism (plant, animal, fungus or bacterium) that is not native and has negative effects on our economy, our environment or our health.” When it comes to rainbow trout, we’re likely a long way from that situation, he says.

That, however, cannot be said in every region through which rainbows swim. From the northern Pacific they’ve made their way, or had their way made for them, to every continent except Antarctica, says von Finster.

Down the road from us, the rainbow - once confined to rivers draining to the Pacific Ocean - is causing headaches on the eastern slope of the Rockies. They’re hybridizing with an endangered species of native cutthroat trout. This can threaten biodiversity, says von Finster. Attempts are now being made to block the rainbow’s access to some eastern-slope waters.

In the late 19th and early 20th century, technology gave rainbows a boost in their inadvertent quest for world domination. The hard-fighting trout was so loved by European anglers that a small industry developed to meet their angling needs, wherever they were sent by their respective empires. After engine-powered ships replaced sailing craft and modern refrigerators were developed, rainbow eggs were distributed globally - including in eastern North America, Europe, Australia and India.

Because rainbows are robust, tenacious and voracious, they have often proved more than a match for smaller native fish in these far-flung rivers.

Von Finster began his fieldwork in May 2013. Informed by his personal experiences and by text research, he placed minnow traps baited with salmon eggs in promising rainbow waters. “The rainbow are very vulnerable to baited minnow traps,” he says. Only a handful of species enter these traps, including the two major ones - slimy sculpins and Chinook salmon, a close relative of the rainbow. A trap left in overnight can bring up more than a hundred Chinook.

The biologist says there must be more at work than simple hunger when it comes to Chinook, rainbows and baited traps. “Personally, I think there’s a pheromone at work,” he says. “Something else is pulling them in. I have to think it’s a chemical marker.”

Whatever the lure, no huge surprises were lifted from the water in 2013. Reports and casual anecdotes were confirmed, including a small population in Laurier Creek. The rainbow are holding on in a select area, but do not appear poised to upset a natural order of the upper Yukon basin.

The field work and the studies are complete for now, though von Finster cautions that this was a one-year field study, and that 2013 was a cool, high-water year. Further work during a warm, low-water year, might yet provide new information.

His 2013 report will provide a digitally available baseline should future researchers need it, von Finster says. The information is now in place should rainbow trout populations expand and threaten the ecosystem. While it’s not worth a rainbow-specific public-awareness campaign today, these fish could be worked into future presentations on invasive species, says the biologist. Oncorhynchus mykiss might help answer the nagging question: Should species be manipulated to suit human priorities of the moment?

This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at