Having lived there for some time I would look for natural causes first such as over population and then man made causes such as shortage of natural food supplies. The rape of the salmon population in all parts of it's four year Pacific Ocean circling cycle cannot be stopped by the efforts of one country nor one country that allows foreign fishing boats to catch what they will NOR some of the dirty tricks pulled on our population as well as the fish by such entities as the US Government and Tyson's to name one.

Some years ago the Fed decided to cut down on our fishing industry by limiting licenses. They bought out a high number of trollers and trawlers. (long line and net boats). Put the former US crews into various retraining programs. THEN decided to sell the boats to the Russians ostensibly for use off their coasts. The buy out and the sale was subsidized by guess who? The buy out and the US Taxpayer.

The new Russian boats didn't go to the western Pacific instead they fished off our shores and guess who bought the fish, provided dock space in Seattle and installed new fish processing plants (Fife Washington.)

The same lack of care has brought down the crabbing industry as well.

You want to know who starves the seal pups? Look no further than Washington DC but also look at the seals themselves. Harbor Seal are considered pests that strip their local areas of food and take over not only water but the dock spaces.