Have not seen a fischer cat but have heard the SOB and that's an eery freaking sound.
I thought I was hearing a fisher cat up in the woods behind my house for quite a while -- usually heard it in the hour or two just before dawn. Not every night, but sometimes two or three nights in a row, then I might not hear it for another week. Horrid sound. I could only describe it as an angry, hissing, growling, screech.
Anyway, one night, it woke me up. Sounded like it was right outside my window. Neighbor has a cat that often craps in the flower bed there, so I figured it might have just met its maker at the teeth of a fisher cat. Got up, went to the window and hit the back light. Bobcat. And not a very big one. It ran into the woods, stopped and screeched. Turned out my fisher cat was a bobcat all along.
Talked to a wildlife biologist about it, and he said most of the fisher cat "unseen but heard" stories in CT are much more likely bobcats than martens.