Some of my thoughts regarding such abberations although they may not be such: I believe there's some complexities in our coastal rainbow stocks that have been either ignored in the realm of "big picture" management/science or just haven't shown up on the screen yet. Year to year variability in abundance of a unique stock variation may have caused you to run into this possible variant if it does in fact exist. One of the basics of such discoveries of new stuuf mother nature has kept secret from us is the occurrence of scientist or persons of knowledge.
Never ceases to amaze me how the "she" does this to my foundations of knowledge, beliefs and assumptions every year.

Taking pictures, recording info on the time and place of catch, scale samples and such would go a long way towards the learning curve on these subjects.

Gooose