These play a vital role in the subsistence lifestyles of many peninsula residents and ease travel, hunting, and fishing. Most peninsula rivers have at least a small yearly run of several varieties of salmon, as well as Dolly Varden, Arctic Grayling, whitefish of various species, Northern Pike, and Burbot. Most rivers on the Seward Peninsula freeze in mid-October; spring break-up usually occurs in mid- to late May.