It shouldn’t have been as easy as it was, but, considering how few flies these massive rainbows see over the course of a season, I guess I shouldn’t have been surprised. Sure, the river looks plenty fishy, and its features are Rocky Mountain-typical: long runs, undercut banks and then a stretch of aquarium-clear water that flows quietly among the willows until it dumps into one of several lakes as it courses south and west. But, as the first sizable, deeply striped rainbow gulped a size 12 Adams cast kind of nonchalantly to the bank, I did a double take.