Rainbow Trout Migration and Use of a Nature‐Like Fishway at a Great Lakes Tributary

Rainbow Trout Oncorhynchus mykiss were monitored over two consecutive vernal migration periods at a nature-like fishway on the Beaver River, Ontario, to assess attraction efficiency, passage efficiency, multiple fish passage metrics, and interannual return rates from Georgian Bay, Lake Huron. Fishway evaluations have shifted to fill knowledge gaps related to the passage of nonsalmonids; however, surprisingly little work has been conducted with Rainbow Trout, with no known study assessing attraction or passage at a nature-like fishway. Attraction efficiency was 53% and passage efficiency was 100% in 2017; only two of the radio-tagged fish returned to the fishway in 2018. Upstream passage through the fishway required an average time of 152 +/- 122 min. Fish spent 19-43 d upstream before returning to Lake Huron, where downstream passage required as little as 15 min. Overall, there were no significant relationships between any of the fish passage metrics and fish size or condition. These results can be used as a foundation for anadromous O. mykiss subspecies passage research and suggest that fisheries managers may need to adjust annual fishway counts. Future research should focus on developing methods to directly integrate temporal passage metrics into estimates of fishway efficiency.