I believe it's a fallfish, which is a close relative of the much smaller creek chub.
That is not, however, a cisco. Cisco (aka lake herring) are relatives of the whitefish, as swede says, but very different from fallfish and chubs, which are minnows. Cisco are cold-water fish usually found deep in the middle of large lakes. Where they exist, lake trout tend to grow big on them.
