The Northwestern Pond Turtle (Actinemys marmorata) is the only native freshwater turtle on the west coast.
Red-eared Slider (Trachemys scripta elegans). Red-eared Slider turtles are not native to California, but because they are popular pets, released turtles have become an invasive species.
By 2019, it appeared that all of the turtles at the lake were Red-eared Sliders (Trachemys scripta elegans). Here they are enjoying the sun next to a Double-crested Cormorant.
In the Fall of 2020, the lake level was extremely low. The floats that the turtles usually hung out on were left high and dry. Several climbed up on an old tree trunk that had been under water before the lake level dropped. The turtles on the upper part of the trunk are Red-eared Sliders, but the one on the lower left is a Northwestern Pond Turtle. I was happy to see that some pond turtles are still living in the lake!
A little closer look at the Northwestern Pond Turtle.