The last discovery concerned a dead grey whale in Turnagain Arm, a narrow glacier-fed channel off Anchorage where grey whales rarely venture.
According to Michael Milstein, a NOAA's Fisheries Service spokesman, after examining the dead whales, the current hypothesis is the animals failed to eat enough last year in their summering grounds in the Bering and Chukchi seas off Alaska.
He continued that grey whales do most of their annual feedings in Alaska, where they pack on the fat that sustains them until the next summer.
As Mr Milstein commented
People think that clearly something happened up there that led the whales to not get as much food. Given that they put on the bulk of their weight in the summer season up there, the die is sort of cast there.
Additionally, the Bering and Chukchi seas have been warm since 2016, with record or near-record high sea surface temperatures and an unprecedented lack of sea ice. In addition, winter ice in the Bearing sea was the lowest in a record that stretches back more than 150 years, and ice this past winter was almost as low.
Therefore, the lack of sea ice and warmth have been linked to having contributed to disruptions in the Bering and Chukchi seas, including bird and seal die-offs.
In light of the above, Rick Thoman, a climate scientist at the Alaska Centre for Climate Assessment and Policy highlighted
It affects the whole food web from the algae to the krill on up.
Moreover, many dead whales have been found in San Francisco Bay and Puget Sound off Seattle. There's a possibility that the whales stop in these areas to look for food or find a place to rest.
Concluding, another theory is that the Eastern North Pacific grey whale population has grown so large, to about 27,000 animals, they may be competing for food.
As you have more whales in the population, more whales are going to die from time to time.
... Milstein concluded.