Evaluation of Downstream Passage Alternatives for Shortnose Sturgeon

摘要

A laboratory evaluation was conducted for the Holyoke Gas & Electric Department in a largernflume at Alden Research Laboratory to determine the engineering and biological criteriarnnecessary to guide shortnose sturgeon to a 2-ft square bottom bypass entrance in a 10-ft widernsection of steel bar rack with 2-in clear spacing. Tests were conducted with yearling shortnosernsturgeon (mean length:332 mm) in a 80 ft L ×20 ft W × 8-ft D test flume. A constant approachrnvelocity of approximately 2.2 ft/s was maintained at the face of the bar rack for all trials. All testrnfish were fitted with externally attached PIT tags to track fish movements at two locationsrnupstream of the bar rack and in the bypass. Test conditions included bypass entrance velocitiesrnof 1, 2, 5, and 6.2 ft/s. In addition, trials were conducted under nighttime light conditions withrnand without illumination of the bypass entrance. Finally, based on the bottom-oriented behaviorrnof sturgeon, additional trials were conducted to determine the effectiveness of bottom-mountedrnguidance ridge structures for guiding sturgeon towards the bypass entrance. The ridges wererntwo 1.5 × 0.75-in plywood strips angled from each flume wall downstream towards the bypassrnentrance. Data were collected with submersible video cameras (day tests), a DIDSON acousticrncamera (night tests), and a PIT tag system. Effectiveness of each test condition was measuredrnas the percent excluded from entrainment, the percent bypassed, and the overall bypassrnefficiency (number bypassed divided by the total entrained and bypassed combined). Percentrnexcluded, percent bypassed, and bypass efficiency generally increased with increasing bypassrnentrance velocities, but peaked at 5 ft/s. At 5 ft/s, 82% of sturgeon were excluded, 33% werernbypassed, and a bypass efficiency of 64.3% was achieved. Trials conducted at night at arnbypass entrance velocity of 5 ft/s without illumination of the bypass entrance achieved a higherrnpercent bypassed (67%) and bypass efficiency (70%), but a lower percent excluded (71%).rnIllumination of the bypass entrance did not increase bypass use at night. Trials conducted at 5rnft/s with bottom-mounted guidance ridges yielded the highest percent excluded (87%) andrnbypass efficiency (74%). Video, DIDSON, and PIT tag data indicated that sturgeon passedrndownstream more quickly at higher bypass entrance velocities and at night. The bottommountedrnguidance ridges were effective in delaying downstream passage, minimizingrnentrainment, and increasing bypass use. With additional testing of alternative designs,rnguidance ridges leading to a bottom bypass may have potential to improve downstreamrnpassage of sturgeon at hydro project intakes.