The primary effect of barriers (e.g., hydroelectric dams, water storage projects, irrigation diversions, impassable culverts, etc.) on Pacific salmonids is the reduction in population abundance and productivity through excessive mortality and reduction in habitat quantity and quality. Individuals are lost to the population due to death from passing through turbines, disproportionate predation in reservoirs, entrainment at unscreened or improperly screened diversions, etc. Spatial structure and diversity have also been reduced by the loss of nearly 40% of salmon habitat from dams (NRC 1996), either through complete blockage or inundation.

This document is intended to assist with improving conditions for salmonids that must migrate past barriers to complete their life cycle. The task involved in successfully passing fish upstream or downstream of an in-river impediment is a dynamic integration of fish behavior, physiology, and bio-mechanics with hydraulic analysis, hydrologic study, and engineering. Installing a fish passage structure does not constitute providing satisfactory fish passage unless all of the above components are adequately factored into the design.

The following document provides criteria, rationale, guidelines, and definitions for the purpose of designing proper fish passage facilities for the safe, timely, and efficient upstream and downstream passage of anadromous salmonids at impediments created by artificial structures, natural barriers (where provision of fish passage is consistent with management objectives), or altered instream hydraulic conditions.

This document provides fishway facility design standards for the National Marine Fisheries Service, and is to be used for actions pertaining to the various authorities and jurisdictions of NMFS, including Section 18 of the Federal Power Act (FPA), the Endangered Species Act (ESA), and the Magnuson-Stevens Fishery Conservation and Management Act (MSA) in the Northwest Region (NWR). This document intends to provide generic guidance as an alternative to active participation by NMFS engineers in a design process, for the purpose of providing designs that will be acceptable for fishways that fall within NMFS jurisdictions. If passage facilities are designed and constructed in a manner consistent with these criteria, adverse impacts to anadromous fish migration will be minimized.

Instances will occur where a fish passage facility may not be a viable solution for correcting a passage impediment, due to biological, sociological, or economic constraints. In these situations, removal of the impediment or altering operations may be a suitable surrogate for a constructed fish passage facility. In other situations, accomplishing fish passage may not be an objective of NMFS because of factors such as limited habitat or lack of naturally occurring runs of anadromous fish upstream of the site. To determine whether NMFS will use its various authorities to promote or to prescribe fish passage, NMFS will rely on a collaborative approach, considering the views of other fisheries resource agencies, Native American Tribes, non-government organizations, and citizen groups, and will strive to accomplish the objectives in watershed plans for fisheries restoration and enhancement.

This document does not address aspects of design other than those that provide for safe and timely fish passage, and to some extent, preservation of aquatic habitat. Structural integrity, public safety, and other aspects of facility design are the responsibility of the principal design engineer, who should ensure that the final facility design meets all other requirements in addition to the fish passage criteria and guidelines contained in this document.