How does the thermocline decide where summer walleye live?

In a stratified lake the walleye is squeezed from both sides: surface water pushes past its comfort range of 18–22 °C (64–72 °F), while the cold water below the thermocline often runs out of dissolved oxygen as the season wears on, especially in fertile lakes. The livable slice is the band at and just above the thermocline — commonly somewhere in the 6–12 m (20–39 ft) range — and in lakes with cisco or smelt, that same band is exactly where the forage stacks, which is why summer graphs show walleye layered like a stripe across the basin. Find the thermocline on your electronics (it often paints as a faint line), and you have eliminated most of the lake's volume before making a cast. In shallow, well-mixed lakes this logic simply does not apply — there, weeds, wind, and light run the show.

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