Dave great info. Does the lake have much shallow turbidity along with the plants? That might also increase the probability of crossing due to masking of visual cues.

Any indication of alternative male reproduction strategies in GSF (sneakers/cuckholders)? If so that may account for some natural crossing. That is male GSF sneakers/cuckholders moving in on male BG nests just as the female BG deposits her eggs. Could also happen with BG sneakers moving in on GSF nest as the female GSF deposits her eggs.