From the New Hampshire Fish and Game web site...
"Contrary to popular belief, house cats are not a regular food item for fishers. Scientific studies show that fisher prefer to eat small prey species. Mouse-sized mammals make up about a third of their diets, and a smaller proportion is snowshoe hare. Most of a fisher's diet consists of mice, small birds, fruit and berries, as well as deer in the form of carrion. Cat hairs were found in only one of over 1,000 stomachs examined in 1979 and 1980."
http://www.wildnh.com/Wildlife/Wildl...ort_112003.htm
Dan