Some factors influencing the trends of salmon populations in Oregon

Abstract

Three factors were found to be significantly correlated with the fluctuations and trends in silver salmon production in Oregon. Logging was found to adversely affect the runs of salmon in later years. Exceptional winter floods seem to produce poor resulting runs. Low summer water flows also appear to produce lower than average runs on some rivers, while higher summer flows appear to be followed by an increase in the resultant runs. The intensity of fishing was also found to affect the subsequent productivity of the fisheries. Increases in fishing effort on the rivers studied were followed in succeeding cycles by a lower catch, and when the fishing effort declined the ensuing production of silver salmon generally increased. Other factors studied did not bear a significant relationship to the fluctuations or trends of productivity of silver salmon.