Biology, Management, and Protection of North American Sturgeon

<em>Abstract.</em>—We evaluated the ability of juvenile lake sturgeon <em>Acipenser fulvescens</em> and shortnose sturgeon <em>A. brevirostrum</em> to guide along various configurations of angled bar racks and louvers in a laboratory flume. Young-of-the-year (YOY) lake sturgeon were evaluated with the guidance arrays angled at 45 and 15 degrees to the approach flow, and age-1 lake and shortnose sturgeon were evaluated only with the guidance structures set at a 15 degree angle. The YOY lake sturgeon, also, were evaluated with a perpendicular bar rack and with no guidance structure in place. We estimated guidance efficiency at three approach velocities (0.3, 0.6, and 0.9 m/s) by determining the percentage of released fish that were diverted to a full-depth bypass. Guidance efficiency of YOY lake sturgeon was low (<37%) for all bar rack and louver configurations evaluated. The highest guidance efficiencies for YOY lake sturgeon occurred at an approach velocity of 0.3 m/s, and the lowest guidance levels were observed at 0.9 m/s. All YOY lake sturgeon were entrained (i.e., 0% guidance) during tests with the perpendicular bar rack and with no guidance structure in place. There was little difference in YOY lake sturgeon guidance efficiency rates among the various configurations of angled bar racks and louvers that were evaluated with respect to slat spacing, structure angle, and the presence or absence of a solid overlay on the bottom 30 cm of the guidance structures angled at 15 degrees to the approach flow. Guidance efficiencies for age-1 lake and shortnose sturgeon were high, exceeding 90% at all velocities, during tests of the 15-degree bar racks and louvers with the solid bottom overlay installed. The lowest shortnose sturgeon guidance efficiency (83.3%) occurred during the evaluation of the louver without the overlay in place at a velocity of 0.6 m/s. The large difference in guidance rates between the YOY lake sturgeon and the age-1 lake and shortnose sturgeon was most likely due to swimming capabilities associated with fish size. Based on the sizes of the fish we evaluated, the use of angled bar racks and louvers may not be appropriate for sturgeons less than about 200 mm in length, whereas they may be viable guidance technologies for larger fish.