The mink in Alaska give birth just prior to the arrival of chinook on the spawning grounds. This allows the mothers, who consume the salmon, to produce lots of good milk.

Perhaps the orcas, particulalry females, target chinook as a source of high quality fats, for lactation soon after birth. Lacking the high fat food supply at that time of year, calf survival may be reduced. The temporal and spatial issues of when they eat chinook needs tyo be looked at.

Obviously, they won't be eating them all year in Puget Sound because they probably weren't here in great numbers all year. But, their presence at particualr times and places may be critical.