So here was my "reasoning" this time around (I actually went with my initial reaction and did not let the "reasoning" win). My initial impression was chinook (reenforced by the spots on the tail and Rod's pointing out that it was about 50cm - the official size limit of a jack spring). However, when examining the photo to try to use the three characteristics needed for a positive ID, I begin to question that initial reaction. In the photo, those gums (which Rod, in his explanation, says are black) looked white (suggesting a coho) as did the shape of the anal fin (the lead ray extends to the mid point not 1/3 the length) which is probably have a reflection that this is an immature fish. It is a good thing we get to look at the live fish when we are fishing (where, as a few of mentioned in other threads, you can use smell too).