Behavior and movement of smallmouth bass (Micropterus dolomieu) near Bonneville Dam, Columbia River, Washington and Oregon, March–October 2022

A telemetry study was conducted during March–October 2022 to evaluate behavior and movement patterns of adult smallmouth bass (Micropterus dolomieu) in the forebay of Bonneville Dam, on the Columbia River in Washington and Oregon. This study was a follow-up to a previous study conducted at the site during August–December 2020. In 2022, a total of 41 smallmouth bass were collected, tagged, and released during March–May in three distinct areas of the dam forebay and monitored until late-October. Movement data from 39 tagged smallmouth bass were used in behavior analyses with an average detection duration (elapsed time from release to last detection) of 121.5 days. Most tagged smallmouth bass had site fidelity while present in the forebay of Bonneville Dam, primarily remaining within their zone of release, or moving into nearby adjacent zones. Although site fidelity was common during the study, we found that some tagged smallmouth bass left the forebay of Bonneville Dam and moved substantial distances upstream or downstream. Thirty-six percent of the tagged smallmouth bass were detected at least 8 kilometers upstream or downstream from the Bonneville Dam at some point during the study period (several of these fish eventually returned to the forebay), and 10 percent of the tagged fish were detected at sites located 24 river kilometers upstream or downstream from the dam. Results from this study build upon previous data collected during 2020 and provide new insights into behavior patterns of smallmouth bass collected and tagged in the Bonneville Dam forebay.