Using the thermocline to catch kokanee

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What is a “thermocline?”

Read on and you’ll hopefully catch more kokanee salmon.

When trolling for kokanee salmon in late summer have you ever asked, or been asked, “How many colors?”

In northwest Montana, trolling a string of large spinning blades like Cowbells or Ford Fenders is the most popular way to catch tasty land-locked sockeye salmon.

The fish aren’t big, but limits are liberal and they taste SO good!

The number of colors refers to color-coded leaded line which helps sink the flashers and small baited lures. In general, the more colors out of the rod means fishing deeper.

This week’s story isn’t so much about how to catch kokes, but rather how to find them in the water column.

In short, kokanee will congregate in water temperatures in which they feel most comfortable.

Not too warm. Not too cold. Just right.

In spring, in most area lakes over 30 feet deep, the sun warms surface waters and as the summer gets hotter, the warmed layer grows deeper.

Less dense warm water is supported by colder, denser water that sinks.

The interface between the warmer, upper water and the cooler, denser lower water is called the “thermocline”, where water temps may drop 10 to 20 degrees within just a few feet of depth.

Last week I lowered the temp sensor on my Aqua-Vu camera down 60 feet, reading the temperature every foot.

In a protected bay, the water temp dropped from 65 to 54 degrees from 35 feet to 40 feet. In 200 feet of open water, temps dropped from 68 to 54 degrees from 27 to 34 feet of water.

Kokes tend to congregate just above the thermocline, which obviously varies throughout a lake.

In other words, trolling all over a lake all day at 4½ colors may not give you the best opportunities to catch kokes.

Good luck!

Jerry Smalley’s Fishful Thinking column appears weekly in the Hungry Horse News.

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