Upstream swimming performance of adult white sturgeon: Effects of partial baffles and a ramp

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 x 2.1 m wide x 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., 0.5-14.68-m/s) sections for rest and recovery.