Natural Encounters has several comments on turtles, or lack of them, at Clark Lake. The latest is from John Deming (view others by scrolling down).
I suspect all of our turtle population is going into significant decline as a result of our continued attempt to make the lake into a “pool” rather than a natural body of water. Turtles require land to lay their eggs. Sandy soil is better, easier to dig a nest for laying eggs. Sea walls are a barrier to turtles to areas that they can use to lay their eggs. If we don’t have accessible areas for the turtle to lay their eggs, the turtles will disappear. It is interesting that the government agency that is responsible for maintaining the natural environment, the DNR, issues permits for sea walls that prevent turtles from nesting sites.