After Petersburg, a squeeze through the self-explanatory Wrangell Narrows took us south into the Clarence Strait, prime hump-backed whale territory. A group of hump-backs were soon spotted off the stern and we took skiffs out for a closer inspection. We had seen a number of them a couple of days earlier in Glacier Bay, but not like this. Here, a group of ten or more were ‘bubble-netting’ for herring. This rare co-operative feeding behaviour involves a group of whales diving deep and producing bubbles from their blow-holes to create an underwater curtain of bubbles that traps the small fish that the whales feed on. Herrings hate bubbles and will do all they can to avoid passing through them and so what the cunning whales do is to create a net of them that traps the disoriented fish before they rise en masse to the surface with mouths agape to scoop them up. Gulls – Bonaparte’s Gulls mostly, I think – take advantage too, grabbing those fish that manage to escape the whales’ enormous gaping jaws. In fact, it is excited gulls that tend to give away the location of the any imminent bubble net. It is a magnificent spectacle: ten 50 foot whales all hitting the surface together is an unforgettable, quite humbling sight; a phenomenon that gives new meaning to the term awe-inspiring. In less than an hour, we saw it happen four or five times
Southeast Alaska’s Clarence Strait, west of Prince of Wales Island, is one of the best locations to see this behaviour. Nevertheless, it is still very rare. Karl, our guide, reckoned that of, say, 25,000 hump-backed whales in the North Pacific maybe just 100 practised bubble-netting in groups like this. It has only ever been observed in southeast Alaska. We had just seen 10% of the world’s cetacean elite doing this very thing – a rare privilege indeed.