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

Beyond headloss: do we have the right ecological and hydraulic metrics to determine successful fish passage in rock ramp fishways? (#129)

Tim Marsden 1 , Ivor Stuart 2 , William Rice 3
  1. AFPS, Fern Bay, NSW, Australia
  2. Kingfisher Research, Melbourne, Victoria, Australia
  3. Mountain-Prairie Region, U.S. Fish and Wildlife Service, Denver, Colorado, USA

Rock ramps are nature-like fishways that provide fish passage and aquatic habitat in rivers by simulating hydraulically diverse riffles and pools found in natural environments. The design of these ramps has typically been conducted with simple parameters (i.e. headloss) and 1-D modelling techniques common for other fishways. However, while it has been realized that 2-D and 3-D modelling more closely simulate the dynamics of a rocky ramp environment, even then they do not adequately capture the full ability of these ramps to provide fish passage, through their rocky environment and interstitial areas. The inadequacy of current design and modelling to capture actual fish passage, especially of small fish, will be discussed by comparisons to existing fish monitoring or observational data on select projects that were deemed barriers by current evaluation standards. The authors propose that monitoring live fish for fish passage success at rocky ramp projects be the primary tool for their passability, at least until sufficient data is collected that we all as a community learn what parameters are most effective in rocky ramp design.