Breakfield and King are two of the people who have the chore of catching the rainbows and tagging and inspecting them. The fish must be handled very carefully to avoid injury or death, but the information recorded from the fish is invaluable. Each fish caught is first handled properly by being netted, but not removed from the water. The length of the fish is measured from snout to fork, and it is examined for sex, fin wear, mouth damage, spawning condition and parasites in the gills. A fish 20 to 22 inches long is estimated to be about 8 to 10 years old.
Fin wear indicates spawning information.
The condition of the caudal fin can show recent wear, old wear or no wear, which indicates the fish's history of digging its redd, or nest. The fish's mouth also is examined. This fish population has a high percentage of mouth damage, a condition found in the majority of large spawners. Spawning conditions are categorized. A mature spawner is full of eggs or milt.