For the first time since commercial whalers of past centuries were killing them — legally or illegally — there is now comprehensive accounting of whale abundance in the Gulf of Alaska.
New data about abundance and distribution shows that the Gulf of Alaska is important habitat for whales and porpoises, including some species that are extremely rare and others that are now thriving, more than three decades after international commercial whaling ended.
The results, in a study by scientists at the National Oceanic and Atmospheric Administration published in the journal Marine Biology, is the product of extensive surveys conducted in 2009, 2013 and 2015.
The most abundant whales and other cetaceans in the Gulf of Alaska, the surveys found, are fin whales, humpback whales and Dall's porpoises. But even extremely rare species were spotted — blue whales, which were rarely seen in prior years, and beaked whales, which are elusive because they swim to great depths off the continental shelf and rarely come to the surface.
In all, the surveys tracked whales and other cetaceans from six of the 14 species known to use the Gulf of Alaska.
Not seen were some of the rarest whales on earth — North Pacific right whales. Once plentiful, North Pacific right whales were nearly wiped out by commercial hunters who valued the animals for their high fat content. Because their fat kept their harpooned bodies afloat and easy to retrieve, they were considered the "right" whales to kill, according to commercial whalers' lingo.
Now there are only about 30 North Pacific right whales swimming in waters off Alaska, according to NOAA, and perhaps a few hundred in Asian waters, according to the International Union for the Conservation of Nature. They are considered the world's most critically endangered whales.
North Pacific right whales have been spotted and photographed in the Bering Sea, but the scientists sailing the Gulf of Alaska in the recent surveys were unable to make any sightings.
That was "incredibly disappointing," said lead author Brenda Rone, a marine mammal scientist with NOAA's Alaska Fisheries Science Center who has focused on Pacific right whales.
"As we surveyed along and the days ticked by, I couldn't help but reflect back to the whaling records. Right whale catches spanned across the entire Gulf, and we were unable to locate a single individual. It was very sobering to experience, firsthand, the impacts of whaling on this species," Rone said in an email.
The scientists did detect some underwater calls made by right whales, however.
And the sighting of blue whales was a happy outcome, a good sign for that endangered species, Rone said.
More work is needed to understand what is happening with blue whales in the eastern North Pacific, she said.
"Is this new or is it simply a factor of limited survey effort? Its re-establishment of historic habitats? Increased numbers? Shifts in distribution? It's difficult to say without further studies," she said.
Blue whales are increasing in number in the eastern North Pacific, and several factors could be combining to create that result, she said.
Blue whales are the largest animals known to have ever existed on earth, according to NOAA. The southern hemisphere blue whales are generally bigger than those in the northern hemisphere — and the southern hemisphere population was harder hit by commercial whaling, according to NOAA. The pre-whaling population in the southern hemisphere was believed to be about 175,000 animals but is now down to about 2,000, according to NOAA; in the North Pacific, the pre-whaling population was about 4,900 and is now about half that.