Looking just below the surface of a lake reveals the character of a body of water. The Huntington Mine Pit Lake in the Cuyuna Country Recreational Area is a very diverse body of water from extreme depths of 300-plus feet where the suspended trout live, to the shallows for nesting sunfish, and to standing trees for large and smallmouth bass.
In summertime when the temperatures of the water in area lakes are just too much for whitefish and tullibee to endure, the mine lakes seem to be stable without any evident die-off. Above the thermocline, which is at 17 feet this week, the sunfish and the bass are hunting and feeding in the weeds. Below the thermocline the big northern pike wait for unsuspecting fish to get near. In the clear water of the mine pit lake, the pan fish move in and out of cover, with the tiny sunnies rarely leaving the protection of heavy grass or brush. On the bottom, the clams filter the water for food. As you approach, they close for protection.
Temperatures in the thermocline layer can reach 80 degrees this time of the year. At 17 feet, a wavy area of water separates the extreme temperature difference which can drop to the 40s in a matter of two feet at the depth of 23 feet. Aquatic life flourishes above the layer of water and fish that cannot tolerate the warm temperatures will spend their days below the thermocline. It is a mystery if these cold water fish venture into the warm water above the thermocline to hunt where the abundant life exists. Swimming between these two layers of water is a temperature shock but also illustrates the variation of life that exists above and below the thermocline.
Behind your trail of bubbles, a school of fish follow hoping that anything which is kicked up will reveal a tiny meal. They also have personalities, inspecting the foreigner with the goggles to see their reflection in the glass and nipping at the fine hairs on your ears.