Behavior and movement of smallmouth bass (Micropterus dolomieu) in the forebay of Bonneville Dam, Columbia River, August–December 2020

A telemetry study was conducted during August–December 2020 to evaluate behavior and movement patterns of adult smallmouth bass (Micropterus dolomieu) in the forebay of Bonneville Dam, Washington. A total of 40 smallmouth bass were collected, tagged, and released during August–September in seven distinct areas of the dam forebay and monitored until mid-December. Movement data from 36 tagged smallmouth bass were used in behavior analyses with an average detection duration (elapsed time from release to last detection) of 53.3 days. Nine smallmouth bass eventually moved upstream out of the array and sixteen smallmouth bass moved downstream out of the array. Smallmouth bass showed high site fidelity, primarily remaining within their zone of release or moving into nearby adjacent zones. Tagged smallmouth bass spent the greatest percentage of time in their zone of release in all zones except the Boat Rock zone; the five smallmouth bass released in the Boat Rock zone moved to the Goose Island zone, where they stayed most of their time. Smallmouth bass movements to zones farthest away from their zone of release were not common and smallmouth bass residence time in those zones was short. A large percentage of tagged smallmouth bass moved among three zones located immediately upstream from the Bonneville Dam spillway, which was not operated during the study. Results from the study provided new insights into smallmouth bass behavior patterns during fall months in the forebay of Bonneville Dam.