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[IronNoggin]

Efforts to free Kokanee salmon from 'predator pit' continue

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.

https://www.pentictonherald.ca/spare_news/article_d29c232e-ecf2-5197-b471-99b2ca780548.html

There is much more to this article. I found their approach interesting in attempting to employ angling as a chief method of predator reduction alongside FN netting.

[RalphH]

Kootenay Lake should be a case study to illustrate how hard it is to reestablish a unique ecological balance once humans mess it up. Introduction of mysis shrimp and the Duncan and Libby dams are what messed it up. The shrimp intended as feed for both kokanee and trout turned out to be perfect competitors for the kokanee and they both depended on the same food source. The dams cutoff off the spring flood waters that supple minerals etc that made the lake perfectly balanced for a healthy kokanee population on which the trout and char grew to size of 20lbs plus. The record rainbow from that lake was over 35lbs. Trout over 40lbs were trapped on the Lardeau River spawning grounds when the Province used to sell the eggs to other jurisdictions. it once grew the biggest rainbow trout on the planet.

[clarki]

The article says "According to a 2021 study...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"

I'm curious what happened in 2011 that caused the predator fish to more than double their consumption of kokanee?

The word "suddenly" is an interesting one.

[RalphH]

Kootenay Lake was known for producing small numbers of very large trout. Getting one usually required hours of trolling at relatively high speeds. Average rainbow spawning numbers were historically around 500 concentrated at one small location on the Lardeau River below Trout Lake. I guess a small number of large trout eat far fewer kokanee per year than a large number of smaller fish.

I'd also note this is not the first kokanee collapse - there was one in the late 80s and 90s. BC Hydro funded a lake fertilization program that brought them back in the North Arm but the South part of the Lake and the West Arm never really recovered. I understand the population in the lake south of Crawford Bay is all but extirpated.

Here is a link to Warnock's (et al) article in the Canadian Journal of Fisheries and Aquatic Sciences:

https://cdnsciencepub.com/doi/full/10.1139/cjfas-2020-0410

[wildmanyeah]

I wonder if trout smolts are like chinook smolts and can eat pry up to 2/3s of their size.