Most of the field work was done in three 1-mile sections of the river, that included areas in which salmon were excluded. The number of brown trout, rainbow trout, and juvenile coho salmon that inhabited these sections was estimated annually in April and September. Scales and measurement data were obtained from trout at these times, and also in June and July.

Coho salmon exerted no detectable effect on growth or numbers of young or older brown or rainbow trout, with the exception of young brown trout in the experimental section most heavily used by spawning coho. In this section the coho salmon caused a moderate decrease in brown trout reproduction. For the years 1968 to 1972 there was a significant decrease in numbers of age-0 brown trout in comparison with 1967. But the decreases had little effect on the population of these year classes at older ages. Reduction in number of young brown trout was compensated by a better rate of survival to the older ages.