Overview

The depressed status of Snake River stocks of chinook and steelhead and the recent listings of many salmon stocks in the Columbia Basin have led to several analytical evaluations and management advice aimed at recovery of these stocks. These different analytical reviews address the effectiveness of different hydrosystem options as well as the potential for recovery through improvements that increase survival at other life stages (e.g., habitat, harvest). Hydrosystem options evaluated included status quo, maximizing transportation, and the option of breaching the lower four dams on the Snake River (also called drawdown and natural river options), the main topic of the Lower Snake River Juvenile Salmon Migration Feasibility Report / Environmental Impact Statement (USACE). The first review was completed by PATH (Plan for Testing and Analyzing Hypotheses), an open forum composed of modelers, fishery biologists and statisticians from all three states (Oregon, Washington, and Idaho), the federal government (Army Corps of Engineers (USACE), US Fish and Wildlife Service (USFWS), National Marine Fishery Service (NMFS), Bonneville Power Administration (BPA), the treaty tribes of the Columbia Basin (represented by the Columbia River Inter-tribal Fish Commission -CRITFC), and the Northwest Power Planning Council (NPPC). The PATH approach was based on a decision analysis that showed which management actions are the most robust to remaining uncertainties (i.e. the least risky) and allows a decision to be made with full consideration of uncertainty and risk. PATH analyses were followed by the NMFS effort called CRI- the Cumulative Risk Initiative. CRI analyses explore the demographic effects of hypothetical reductions in mortality at different life stages based on current conditions. PATH and CRI analyses were followed by an analytical comparison of their approaches and results completed by a sub group of PATH composed of scientists from the states of Oregon, Idaho, Washington, CRITFC, and the USFWS. In addition, specific analyses have considered the potential for improvement at certain life stages (e.g., freshwater spawning and rearing; Petrosky et al., in press) and key uncertainties that affect the likely effectiveness of dam breach (e.g., delayed hydrosystem mortality; Budy et al., in review). This annex synthesizes analyses and results PATH, NMFS CRI, and comparative and follow-up analyses which have been completed since and are summarized here and described in greater detail elsewhere. Although the results vary somewhat among approaches, all available science appears to suggest that dam breach has the greatest biological potential for recovering Snake River salmon and steelhead.

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