Cool stuff.
Keep in mind that they are a native species, and it is very likely they have always been in Pymatuning. Fish populations fluctuate......and maybe the pop. has been better the past few years.
There doesn't seem to be any clear connection between Pymatuning and the Conneaut Lake/swamp/French Creek watershed. I bet it's possible......but like I said they've probably always been in the Pymy/Hartstown/Shenango watershed. Just in low numbers