INTERCHANGE AND ISOLATION OF HUMPBACK WHALES OFF CALIFORNIA AND OTHERNORTH PACIFIC FEEDING GROUNDS

Humpback whales feed in several high latitude areas of the North Pacif ic. We examined the interchange of humpback whales between one of thes e areas, off California, and those in other feeding grounds in the eas tern North Pacific. Fluke photographs of 597 humpback whales identifie d off California between 1986 and 1992 were compared with those off Or egon and Washington (29); British Columbia (81); southeastern Alaska ( 343); Prince William Sound, Alaska (141); Kodiak Island, Alaska (104); Shumagin Islands, Alaska (22); and in the Bering Sea (7). A high degr ee of interchange, both inter- and intrayear, was found among humpback whales seen off California, Oregon, and Washington. A low rate of int erchange was found between British Columbia and California: two whales seen near the British Columbia/Washington border were photographed of f California in a different year. No interchange was found between Cal ifornia and the three feeding areas in Alaska. Humpback whales off Cal ifornia, Oregon, and Washington form a single intermixing feeding aggr egation with only limited interchange with areas farther north. These findings are consistent with photographic identification studies in th e North Atlantic and with genetic studies in both the North Atlantic a nd North Pacific.