Oral Presentation International Conference on River Connectivity (Fish Passage 2018)

Upstream passage and attempt behaviour at a sloping weir by migrating adult river lamprey: are studded tiles effective in improving longitudinal connectivity? (#14)

Jeroen Tummers 1 , Jim Kerr 2 , Pat O’Brien 3 , Paul Kemp 2 , Martyn Lucas 1
  1. Department of Biosciences, Durham University, Durham, United Kingdom
  2. International Centre for Ecohydraulics Research, Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom
  3. Environment Agency, York, United Kingdom

The performance of weir-mounted studded tiles for passing upstream-migrating lamprey (Lampetra fluviatilis) was compared with unmodified parts of a Crump flow-gauging weir and with use of a bottom-baffle fishway on the River Derwent, Northeast England. Equidistantly-studded tiles were fixed horizontally on the weir face near the right bank, forming a 1m-wide treatment lane, neighboured by a tileless control lane. A bottom-baffle fishway was present at the right bank, alongside a hydropower tailrace. Two further left-bank controls enabled, together with right-side controls, comparison of lamprey attraction relative to the dominant flow on the right side. Downstream and upstream ends of the right-hand weir-face lanes and of the fishway, downstream ends of the left-hand weir face lanes, and the entrance of the hydropower tailrace area were instrumented with PIT antennas (n=9 total). Of 395 PIT-tagged lamprey, over 10 release sessions in early winter 2017 (turbines on for 21/43 days), 363 (91.9%) were detected at any of the antennas (mean ± SD minimum delay: 14.8 ± 8.9 days). All lamprey detected at the left-bank antennas (attraction efficiency AE: 255/395 (64.6%)) were detected elsewhere also. The fishway was ineffective (AE: 343/395 (86.8%); passage efficiency PE: 5/343 (1.5%)). However, overall passage using the studded-tile corridor doubled (44/395 cf 22/395) relative to the adjacent bare weir-face route (AE tiled lane: 172/395 (43.5%); PE tiled lane: 44/172 (25.6%) - AE control lane: 257/395 (65.1%); PE control lane: 22/257 (8.6%)). Fewer PIT detections were logged at the turbine tailrace and fishway entrance, respectively, when turbines were on (n=441 and n=700; median [range] river discharge turbines-on: 18.7 [10.5-36.3] m3 s-1) compared to turbines-off conditions (n=1005 and n=2457; discharge: 36.2 [10.4-52.3] m3 s-1). While improved passage efficiency was achieved using surface-mounted studded tiles, further in situ evaluations are needed to optimize their performance.