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

Novel fishway entrance modifications to improve passage for native fish (#34)

Mary L Moser 1 , Steve C Corbett 1 , Matt L Keefer 2 , Kinsey E Frick 1 , Siena Lopez-Johnston 3 , Chris C Caudill 2
  1. Fish Ecology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, Seattle, Washington, USA
  2. Department of Fish and Wildlife Sciences, College of Natural Resources, University of Idaho, Moscow, Idaho, USA
  3. Portland State University, Portland, Oregon, USA

Healthy riverine ecosystems require passage routes at dams for a broader array of species than has historically been targeted. Hence, fishway entrance modifications were made at a large Columbia River dam in northwestern USA. These modifications were designed for Pacific lamprey Entosphenus tridentatus, a species of conservation concern. They feature a variable-width entrance weir and flow disrupters to create velocity heterogeneity near the bottom without affecting attraction flows for salmon and shad. Passive integrated transponders and radio transmitters were used to assess both lamprey and Chinook salmon (Oncorhynchus tshawytscha) passage. Entrance efficiency at the modified entrance was compared to that at a similar, but unmodified entrance before and after modifications. No statistically significant differences in entrance efficiencies were observed for lamprey or salmon. Additionally, a lamprey passage structure (LPS) was installed to provide a lamprey-specific route from tailrace to forebay elevation (31 m). Lamprey were counted as they exited the structure. Pacific lamprey successfully ascended the LPS, with annual counts increasing from 48 in 2010 to 3851 in 2016. Radiotelemetry indicated that Pacific lamprey resumed upstream passage after LPS use and traveled at rates similar to those of tagged Pacific lamprey that did not use the LPS.