Assessment, evaluation, and development of fish passage guidelines

Abstract

Instream barriers such as dams and diversions have been designed and constructed on America's rivers for centuries. In recent decades, the negative impacts from instream barriers on freshwater ecosystems have become more well-known and an industry established focusing on mitigating these negative impacts and restoring freshwater ecosystems. A primary focus of practitioners working to restore freshwater ecosystems has been to reconnect aquatic organisms to their original range through the design and implementation of fish ladders, also known as fishways. Fishways provide passage routes for fish past instream barriers, upstream and downstream. Fishway design in the Pacific Northwest United States focused primarily on anadromous salmonids, more commonly known as salmon (genus Oncorhynchus), due to cultural, economic, and recreational significance of salmon. Salmon are strong swimmers when compared to many other fish species; therefore, fishways designed and constructed specifically to allow passage of salmon may not provide safe, timely, and effective passage of other fishes. The purpose of this document is to present a fishway design resource aimed at providing necessary species-specific background and abilities of weaker swimming fishes and evaluate the applicability of existing fishway design criteria when designing fishways for Bull Trout (Salvelinus confluentus). The fishway resource focuses on Bull Trout and Pacific Lamprey (Entosphenus tridentatus) and will be provided to the United States Fish and Wildlife Service (USFWS) as a draft document for future publishing. An extensive literature review was completed identifying species abilities, background, and comparison to existing design criteria, fishway practitioners were briefed on the project and their opinions related to content and format were solicited, and findings were thoroughly reviewed and discussed by and with USFWS staff. As a result of this project a concise fishway resource has been developed as a draft and template for USFWS staff. Additionally, an evaluation of the applicability of using anadromous salmonid passage criteria when designing passage facilities for Bull Trout was conducted. Lastly, future research projects were suggested to address data gaps in Bull Trout swimming performance and fishway designs for them.