Mon, 30 Jun 2014

Monsters of the Deep

“So what do you think lives down there?” It’s my first question to government biologist Lee Williston about the eerily deep waters of Quesnel Lake. Williston has just told me that the maximum depth recorded here is an astounding 523 metres, making it the third deepest lake in North America and the deepest fjord lake in the world.

“Probably not much,” he replies, dashing my hopes of a Quesnel Lake Monster story. “But there are definitely some big fish in these waters. People have landed rainbows here in the twenty pound range.”

Like the legendary Gerrards of Kootenay Lake, Williston explains that Quesnel Lake rainbow trout are a genetically unique, late-maturing strain that gets big by feeding on kokanee. The result is the largest wild sport fishery in the Cariboo, and one of the few places left on the continent where you can fish for trophy rainbows in a pristine wilderness setting.

“Fishing on Quesnel, it’s not uncommon to see a black bear, grizzly and moose all in one afternoon,” says Williston. “There’s a whole host of iconic B.C. wildlife living in the watershed. It really is the complete wilderness experience.”

Still, the lake’s remote location hasn’t made it immune to concerns about overfishing. In 2003, a study was published indicating that the number of large rainbows in Quesnel Lake had decreased, and a possible contributing factor was overharvest of older trout. As a result, restrictive angling regulations were put in place and continue to be enforced; currently, all bull trout and any rainbows over 50cm have to be released. However, recent observations from anglers suggest trout numbers have rebounded, and there is understandably pressure to revisit the angling restrictions on the lake. However, without data confirming populations have recovered, it is difficult for Ministry staff to make regulation changes. That’s where the HCTF-funded Quesnel Lake Angler Exploitation Study comes in: Williston and other Ministry staff are working to determine what proportion of large rainbow, lake, and bull trout are being caught here, as well as unravel some of the mystery surrounding the behaviours of these unique fish populations.

“We’re committed to increasing our knowledge of fish movements and behaviour within the lake, and ultimately ensuring angling regulations are based on the best available science,” says Williston. “Much of the work leading up to this project focussed on improving our understanding of the ecology of what is a very complicated system. Now that we have a better understanding of what ecological factors are driving changes in trout numbers, we can focus on the interaction between anglers and these fish populations.”

“Our goal is to have regulations that are sustainable, but not unnecessarily prohibitive,” Williston continues. “If the data we collect from this study suggests that we can alter or remove some of the current restrictions, hopefully that will result in increased levels of angler participation and satisfaction at Quesnel Lake. That’s ultimately what we’re after: sustainable wild populations and increased angler effort.”

To obtain the necessary data, Williston and his team are combining the latest in fish-tracking technology with citizen science. So far, they’ve tagged over 400 rainbow, bull, and lake trout with $100-reward tags to encourage anglers to report any tagged fish they reel in. This will allow the project team to estimate the number of large fish of each species that are being caught, which will guide decisions about whether or not to increase harvest rates.


Williston has spread the word about the study to local angling guides and resort owners, and says the response from the local angling community has been positive.

“Just making people aware of and inviting them to participate in this study seems to have increased the level of acceptance of whatever angling regulations end up being implemented, because anglers have been an essential part of the research process.”

In addition to the $100-reward floy tags, 150 of the fish in the study have been surgically implanted with acoustic tags: small, sound-emitting devices that allow researchers to remotely track fish in three dimensions. There are 22 acoustic receivers situated around the lake, recording the movement of the tagged fish.

“The detection rate on these things is just amazing,” says Williston, “We’re only in year two of the study, and we already have more than a million detections. That’s an incredible amount of information gathered about populations we previously knew very little about.”

This data will provide researchers with information about the fish’s survival rates, behaviours and preferred habitats within the lake.

“It’s still early days,” says Williston “but we have already done some preliminary analysis of rainbow trout movement, and it’s incredible. They are covering the entire lake – that’s 128 km in length – and they appear to be travelling that distance several times a year. It really is amazing.”

Researchers are also gaining some insight into another of Quesnel’s mysteries: the unusual circumstance of having both bull and lake trout living in the same lake.

“There aren’t many lakes in BC where you have both species,” says Williston. “One typically outcompetes the other. Through the tracking of these tags, we’ll probably be able to get a better understanding of how they are able to coexist in Quesnel Lake.”

All of the data collected by the study will help ensure the sustainability of this wild system, with benefits that extend beyond the lake fishery. Quesnel Lake rainbow trout also support high value stream fisheries on the Horsefly and Mitchell Rivers, attracting anglers from around the world.

So when can anglers expect to see regulations changes for Quesnel Lake? “We’ll have collected two full years of data this fall. We’ll analyze it, and see what changes we can make for the following season,” says Williston. But his work on the project won’t stop there; the study plans to continue for an additional five years so that the team can track the population’s response to any regulation changes.

“One of the great things about this study is that it’s ongoing,” he says. “The acoustic tags have a five year battery life, so we’ll actually get to see how the management decisions we make are affecting the fish and be able to make adjustments if we find they’re having a negative impact on the populations. We’ll also be doing creel surveys, so we can find out how much angler effort rises as a result of increased harvest opportunities.”

Whatever the results on angling regulations, the Quesnel Lake Angler Exploitation Study is making great strides in ensuring management decisions are based on solid information about the fish populations they pertain to. The information gleaned about the life histories of these fish may take some of the mystery out of Quesnel Lake, but it’s our best bet at ensuring that this unique watershed continues to have monsters (at least of the trout variety) lurking in its depths.

The Habitat Conservation Trust Foundation is the major funder of the Quesnel Lake Angler Exploitation Study, providing over $170,000 in grants for the project. This funding is made possible through surcharges on freshwater angling licences purchased in BC. To find out about other projects supported by angling, hunting, guiding and trapping licence surcharges, click here.