Knowledge of the long-term dynamics of freshwater turtle communities is important if we are to understand fully the impacts of human-induced changes in their aquatic and terrestrial habitats. We present data on a turtle community that has been monitored intermittently for more than 20 years and regularly for more than 10 years (1992–2003). The composition of the community has shifted with a decrease in the dominance of Painted Turtles (Chrysemys picta). This shift reflects a decline in the number of C. picta over the past decade, whereas numbers of other species have remained relatively constant. Adult survivorship of C. picta has declined in the past decade. The proportion of C. picta with watercraft propeller damage has increased, whereas propeller damage has remained constant for the two other species for which we have data, the Northern Map Turtle (Graptemys geographica) and the Red-Eared Slider (Trachemys scripta). Our study suggests that the turtle community in Dewart Lake has shifted from 1992–2003. It seems likely that this shift has occurred because of a decline in C. picta, possibly as a result of increased use of the lake by humans.