OK I checked some of my local fish supply sources and no mention of "Pumkinseed". If memory serves me correctly aren't "Pumkinseeds" some sort of Sunfish?
Yes, Pumpkinseeds belong to the same family as BG and RES and can interbreed with them.
PS's should also be in lakes and rivers in Michigan, there are fish farms that sell them in NY, but I'm not sure about MI.
http://www.fish.state.pa.us/pafish/fishhtms/chap22.htm
