As a teenager in the "70's we too backpacked into the White Clouds. One of the lakes we visited was full of rainbow trout that had the lower part of their bodies a dark black (bluish) belly. They were about 8-9" long and we caught them on every cast just like brook trout can react. I had never heard what they were but used to have pictures of them. Thanks for giving me information.
Answer:
If the fish had long dorsal fins, it is possible that you were catching grayling. They tend to have a body shape similar to a rainbow trout and a blue hue over their entire body.
Otherwise, what you were probably catching were brook trout. Brook trout can have a blue iridescent color during certain times of the year and then become dark to red in color during fall spawning events.
Answered on:
Friday, October 24, 2014 - 10:15 AM MDT