Are the populations of North and South Pacific mixing together?
Usually the two populations do not mix together. Since the seasons of the year are opposite in each hemisphere, the humpbacks of the North Pacific are migrating toward Alaska and Canada in May at the same time the humpbacks of the South Pacific are migrating from Antarctica to Australia and the South Pacific Islands. In October, it goes the other way around. But, there is an exception to every rule: One season, researchers in the northern hemisphere noticed a whale with a fluke that was plain white on the underside. They couldn't find the whale in their photo-ID database and sent the photo to researchers in the southern hemisphere. Australia called right away, "Hey, this is our whale!" In old whaling records there are several instances where the whaling vessels followed humpbacks from the southern hemisphere and wound up in the "Sandwich Islands" (Hawaii).
