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

Arctic Grayling and Denil Fishways: Research to Determine Swimming and Passage Capabilities of Grayling in Relation to Fish Barriers (#37)

Kevin Kappenman 1 , Matt Blank , Joel Cahoon , David Dockery , Audrey Jones , Tom McMahon , Katey Plymesser , Bill Rice , Erin Ryan
  1. United States Fish and Wildlife Service, Bozeman, MONTANA, United States

Arctic grayling, Thymallus arcticus are a species of special concern in Montana, USA and have been petitioned for Endangered Species listing.  The only populations native to the lower 48 states were in Michigan and Montana; the Michigan population is now extinct. Irrigation diversions are common to the river systems in Montana.  They provide necessary water diversion for agriculture, but can be barriers to fish movements. Denil fishways have been installed in irrigation diversions to provide fish passage. Their efficacy for grayling passage has not been well studied. This research followed a stepwise progression from determining base line swimming ability of grayling to performing laboratory experiments to test passage through Denils over a range of water depths. We characterized swimming and passage abilities using a swim chamber, an open channel flume, and a Denil installed within the open channel flume to determine the passage capabilities of grayling in relation to barriers. We performed Usprint tests in a swim chamber to measure the maximum velocity a grayling could swim for 15 s; the approximate maximum duration sprint swimming can be sustained. We tested the “volitional” swimming performance of grayling in an open channel flume to determine passage success, maximum ascent distances and maximum sprint speed over a range of water velocities.   We performed Denil laboratory trials focused on evaluating design parameters such as water depth, velocity, and Denil slope and length. We report passage success on a series of trials using two Denil lengths (1.83 m and 3.66 m) at varying hydraulic conditions. This project paired engineers and biologists to develop metrics that can be used to assess barriers and design passage ways to restore habitat connectivity for grayling. Few research projects have followed such a progressive line of study and this work might serve as a model for other research efforts.