Bruce,

I'll try and throw a scientific spin on it-but this is just my opinion.

Most pacific salmon generally eat the same type of food when in the ocean. Notice I don't say EXACTLY the same. The ocean, obviously, is a huge dinner table and over time, I believe salmonids have become genetically adapted to feeding in certain areas of the ocean....whether it be puget sound, off our coast, off british columbia, or up in the gulf of alaska.

There are a lot of links in the ocean food chain and the food your delicious columbia river springer ate is probably slightly different from the food other chinook eat. Here's an example of how subtle it can be:

Your columbia R. springer ate some shrimp up in the gulf of alaska and a rogue river springer ate shrimp off the coast of oregon and california. They both ate shrimp but the food(say, phytoplankton) the shrimp ate at each location could be completely different thus creating a different flavor in the shrimp which, in turn, creates a different flavor in our 2 sample springers.

Your fish has the good fortune of being adapted to a part ocean that has tasty food! It's metabolism genetics probably figures into how the fish breaks down it's food and absorbs it into it's flesh-another factor in taste.

Didn't mean to ramble, I just found the topic interesting and thought it would be fun to try and elaborate.