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The upstream passage of sturgeon (family Acipenseridae) past barriers such as dams has become a concern of fisheries managers in California. Knowledge about the swimming abilities of adult sturgeon species, particularly with relationship to fish ladders, is limited. Wild adult white sturgeon Acipenser transmontanus (n = 25; total length, 135–198 cm) captured in the San Francisco Estuary and Yolo Bypass toe drain were swum in a variable‐speed aluminum flume (24.4 m long × 2.1 m wide × 1.4 m deep) to evaluate swimming behavior around simulated fish‐ladder‐type partial baffles. Four baffle types (one horizontal ramp and three different vertical slot designs) set in two configurations were tested at three velocity regimes (velocity range around baffles, 0.28–2.52 m/s). In general, faster velocities (0.76–1.07 m/s) cued fish to swim upstream sooner (≤100 s). Among the baffle types, the percentage of successful passage was variable, and no statistically significant pattern was detected. The tail‐beat frequency of fish significantly increased in the high‐velocity (to 2.52 m/s) regions of the flume adjacent to the energy‐dissipating baffles, where sturgeon were able to pass by swimming in bursts, followed by a resting and recovery period in slower water. Successful white sturgeon passage structures should incorporate rapid‐velocity (e.g., 0.84–2.52‐m/s) sections between somewhat slower (e.g., 0.51–0.68‐m/s) sections for rest and recovery.

Concern over passage of sturgeon barriers, has focused attention on fishway design that accommodates its swimming performance. In order to evaluate swimming performance, regarding fish ladder type partial barriers, wild adult sturgeons, Acipenser transmontanus; 121-176 cm fork length, were captured in the San Francisco Bay Estuary and Yolo Bypass toe drain. Hydrodynamic forces and kinematic parameters for swimming performance data were collected in a laboratory flume under three flow conditions through barriers and ramp. The experiments were conducted in a 24.4 m long, 2.1 m wide, and 1.62 m deep aluminum channel. Two geometric configurations of the laboratory model were designed based on channel characteristics that have been identified in natural river systems. At a given swimming speed and fish size, the highest guidance efficiencies of successful white sturgeon passage as a function of flow depth, flow velocity, turbulence intensity, Reynolds number, Froude number and shear velocity observed in the steady flow condition, tested with the horizontal ramp structure, occurred at an approach velocity of 0.33 ms -1 . The guidance efficiency of successful sturgeon passage increased both with increasing flow velocity and Froude number, and decreased both with the flow depth and the turbulence intensity. This study also provides evidence that tail beat frequency increases significantly with swimming speed, but tail beat frequency decreases with fish total length. Stride length increases both with swimming speed and fish total length. The importance of unsteady forces is expressed by the reduced frequency both with swimming speed and fish total length. Regression analysis indicates that swimming kinematic variables are explained by the swimming speed, the reduced frequency and the fish total length. The results emphasize the importance of fish ladder type patchiness when a fishway is designed for the passage of sturgeon.

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