During summer and early autumn, spotted seals occur in Alaska waters from Bristol Bay in the southeastern Bering Sea to beyond Demarcation Point in the eastern Beaufort Sea. Comparatively low numbers are present in the Beaufort Sea. Historically, spotted and harbor seals were considered to be closely related subspecies, both being referred to on occasion as harbor or common seals. Anatomical differences between the two seals and the variability in biological events, such as pupping and molting, have led to classification as separate species. The spotted seal is strongly associated with sea ice from autumn to late spring-early summer and bears its young on the drifting pack ice.
Most harbor seals inhabit ice-free waters year round.
Spots are most numerous on the back and upper flanks. There is considerable variation in background coloration, which ranges from gray white to gray blue. Some Alaska Eskimo names for the spotted seal are issuriq in Central Yupik, gazigyaq in St. Lawrence Island Yupik, and qasigiaq in northern Inupiaq. The spotted seal is of intermediate size when compared to the other true seals occurring in waters adjacent to Alaska. It is roughly the size of harbor and ribbon seals, larger than the ringed seal, and considerably smaller than the bearded seal.