No. The Fisher (Martes pennanti), also sometimes referred to as a fisher cat, is not a feline at all, it is actually part of the weasel family. The Fisher shares the same Genus with Martins such as...
Cats are top predators. Meaning in the wild they are not prey for another animal. However, smaller cats such as pet cats have known to be killed by coyotes and other larger animals.
Depends on where you live. Generally, anything canine (coyote, fox, wolf) can and will kill a cat for food. Dogs can be trained to love cats (I know this as I have two dogs and a cat that love each...