Efforts to free Kokanee salmon from 'predator pit' continue

Trout devour kokanee

For Kootenay Lake’s kokanee salmon population to rebound, the kokanee first need a break from being devoured by the over-abundant rainbow and bull trout, say Ministry of Forests officials. So, in the coming year, the ministry will be ramping up measures to reduce the number of predatory trout in the lake.

“Get out fishing!” was the main message to the public at meetings held at Lardeau Valley Community Hall in Meadow Creek on February 22 and in Balfour February 21.

The meetings were held to provide an update on the Kootenay Lake kokanee collapse and efforts to address it. The population collapsed in the early 2010s after rainbow and bull trout suddenly began eating most of the kokanee in the lake.

Measures to reduce predators include proposals to further loosen fishing regulations for rainbow and bull trout, and continued prize draws for anglers who catch and remove them. The ministry is also partnering with local Indigenous nations to remove trout with nets and fencing, and is continuing to stock spawning channels with kokanee fry.

Ministry officials said they are making headway but more needs to be done to capitalize on the progress.

Will Warnock, aquatic specialist for the ministry, said the Kootenay Lake Anglers Incentive Program (KLAIP) is “probably our most effective predator reduction action to date.” KLAIP offers draw prizes to anglers who drop off their rainbow and bull trout heads from Kootenay Lake at one of four local locations (Woodbury Resort, Balfour Gill and Gift, Crawford Bay Market, Wynndel Foods and Outdoor Gear). Grand prizes in 2022 included a brand-new Ford F150 and a Polaris side-by-side.

To further incentivize angling on Kootenay Lake, the ministry has proposed increasing allowable rainbow trout catches from five to 10 per day and increasing the annual limit from 10 to 20. This would create some of the most generous rainbow trout allowances in the province.

Since 2015, any kokanee caught on the lake must be released, a regulation that will continue.

Other programs include using nets and fencing to remove the rainbow and bull trout. The Ktunaxa Nation and Syilx Okanagan Nation Alliance are involved in this, netting the trout in the north end of Kootenay Lake to stop them getting into spawning streams.

“We see this as more short-term surgical action,” Matt Neufeld, the ministry’s fish and aquatic habitat section head, of KLAIP and other predator reduction measures. “If it doesn’t work in the short-term, we need to re-think the plan.”

Since kokanee numbers in the lake plummeted, the size of the prized Gerrard rainbow trout has also declined as they switch to other food sources. For the Gerrards to regain their former size, they need to have enough kokanee to eat, but the number of kokanee in the lake must first exceed the appetite of both the rainbow and bull trout.

Neufeld reckons it will be a five- to 10-year process for the kokanee to reach this point.

Still stuck in the predator pit

Stocking of kokanee spawning channels will continue, but Warnock says without reducing the number of predators first, the young fish easily get gobbled up by trout. They also only stock the lake using local kokanee eggs to protect genetic purity, so the supply is limited.

Without interventions, he says the kokanee will stay stuck in this “predator pit,” unable to overcome the constant predation.

“If you’re below that threshold, the predators will keep collapsing the prey back down into the predator pit,” said Warnock.

He says the kokanee are beginning to climb out of this pit but still not quite reaching the point where they can achieve “breakout recovery” and return naturally to a healthy population.

“We need to maintain those actions and to be more aggressive in the future,” he said.

A similar situation occurred in Lake Pend Oreille in Idaho, with a quick recovery resulting from the use of large commercial gillnets to remove predatory lake trout and allow kokanee recovery.

Faced with questions about why this was not possible here, Neufeld responded that they are going to try similar nets as a pilot project, but with the large size of the kokanee in Kootenay Lake, it is difficult to get a net that catches trout but not kokanee.

The other problem is that those lake trout were non-native and could be totally removed, while the Gerrard rainbows in Kootenay Lake are themselves a focus of conservation efforts, and there is a conservation threshold for Gerrards that the ministry does not want to go below.

Several attendees at the Lardeau meeting expressed concerns about plans to reduce the number of Gerrards.

Grant Trower spent the past 30 years trying to protect them, helping form the Friends of Lardeau River back in 1989 after the Gerrards went through several periods of decline.

“I want to make sure we keep that in perspective,” Trower said. “These fish aren’t anywhere else on the planet.”

The collapse

The kokanee population began collapsing between 2011 and 2012 after the number of rainbow and bull trout soared.

According to a 2021 study led by Warnock and published in the Canadian Journal of Fisheries and Aquatic Sciences, rainbow and bull trout historically ate 29.3% of Kootenay Lake kokanee each year. In 2011, they suddenly ate up 78.7% of all the kokanee biomass in the lake.

The ministry’s current direction is based on the recommendations of this study, which describes many of the possible causes of the collapse, ultimately concluding “a destabilizing force is necessary to recover to the former equilibrium.”

Because kokanee don’t return to spawn for three years, fisheries biologists didn’t realize what was happening until 2015, when all of a sudden there were very few kokanee returning to spawning channels where most fish counting is done.

But by 2015, it was too late; the kokanee population had collapsed.

At first, it was mostly the Gerrard rainbow trout feasting on the kokanee, but bull trout are now eating equal amounts as the kokanee are harder to find and the bulls are better hunters.

The removal of a keystone species like the kokanee is having cascading effects. The predators are getting smaller and leaner after switching food sources. “They’re a lot smaller now,” Warnock said. “They’re basically making do with less.”

The reasons for the initial surge in the rainbow and bull trout population is still not totally understood, but the Warnock study suggests that climate change is causing trout spawning to be more successful and nutrient fertilization of the lake is causing trout survival to improve.

The fertilization program includes the release of mysis shrimp and began after dam building reduced nutrient flow into the lake. It is done to actually help species like the kokanee, but the trout are also feeding on the mysis shrimp, allowing them to sustain their numbers even after they’ve eaten all the kokanee.

“So, rather than starving to death, they can switch to different food items,” Warnock said.

This has meant continued pressure on the kokanee and their continued inability to get out of the predator pit.

As the ministry attacks this problem from all angles, they are using engagement sessions like the one in Lardeau and another in Balfour on February 21 to get the message out, and tell Kootenay Lake residents the best thing they can do to help is go fishing.

“We don’t need a long time, a long reprieve, for kokanee for them to jump up above that critical point where all of a sudden the predators are eating as much kokanee as they need to or want to,” Neufeld said.

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