Recent works shows that the Pinnipeds (Yay Larry) are really chowing down on juvenile salmon. When the whales and pinnipeds are added together, they take more than humans. According to da Feds.
Apparently the SRKW's rely heavily on Chinook because , evolutionarily, they were big and abundant. Down here, we don't Have Chinook, and are working hard to eliminate the other species. The whales are rather fixed in their diets. We have also gotten rid of rockfish, cod, and who knows what else. Further north, the overall abundance of fish allows the whales access to food. Should be noted that Japanese whaling in the 50s resulted in the transient Killer Whales shifting to Sea Otter for a short time. That ended fast as there aren't enough otters to support many whales.
IF Greenpeace and Sea Shepherd get involved then maybe we will see some relief for fish down here. Too much money involved in the fisheries to actually restrict them meaningfully. Plus, those fish have to eat something and we are trying to harvest every little beastie we can find.