On the edge
Hit these subtle hot spots to put more fish in the boat
The thermocline is the fish-rich layer of water that separates the cold, deep water (the hypolimnion) from the warmer surface water (the epilimnion). To find it, I slowly turn up the gain on my sonar unit until it shows a dark, four- to eight-foot band of water. This is the thermocline, filled with zooplankton and phytoplankton and the small baitfish that feed on those microscopic organisms, which in turn attract larger predator fish. It’s an astonishing edge in its own right, but when it also corresponds with the depth of the twilight zone, it’s lethal.