Upstream Passage, Spawning, and Stock Identification of Fall Chinook Salmon in the Snake River, 1992

Intensive monitoring of returning Snake River fall chinook salmon has been a coordinated effort over the last several years. The cooperating entities were the Washington Department of Fisheries (WDF), Oregon Department of Fish and Wildlife, Sez Perce Tribe (NPT), Idaho Power Company (IPC), U.S. Fish and Wildlife Service (USFWS), National Marine Fisheries Service (NMFS), U.S. Army Corps of Engineers, and Columbia River Inter-Tribal Fish Commission. Bonneville Power Administration (BPA) has provided funds and coordination activities. In addition, the Lower Snake River Fish and Wildlife Compensation Program (LSRCP) collected and analyzed genetic data which described the genetic relationships of Lyons Ferry Hatchery (LFH) fall chinook and mid-Columbia upriver bright fall chinook through 1990 (Bugert et al. 1990).

When these fish were petitioned for listing under the Endangered Species Act (ESA), three major questions were left unanswered:

1. What is the fate of 50 percent of the adults that have not been accounted for each year between the counting windows at the first dam on the lower Snake River, Ice Harbor Dam (IHR) and when they were counted as they passed the fourth dam, Lower Granite (LGR)? Potential reasons for this discrepancy include fallback at dams, spawning in the lower Snake River, or pre-spawning mortality.

2. Why do redd counts (observed by helicopter survey) on the spawning grounds above LGR in recent years average only one redd per 8.5 adults passing the dam? As with dam counts, questions remain regarding the accountability of salmon upstream of LGR, and the possibility of deep-water spawning and/or differential spatial spawning distribution between wild fish and hatchery strays.

3. What is the stock composition or genetic profile of returning adults and their offspring above LGR, and how much hatchery straying is occurring?

A study was designed in 1991 by WDF, in cooperation with the USFWS and Idaho Cooperative Fish and Wildlife Research Unit (ICFWRU) to answer these questions. Funding was provided that year by the NMFS, LSRCP, and WDF. Bonneville Power Administration provided funding the second year. This report describes the activities and results obtained during 1992.

Two separate but coordinated methodologies were used in this study. These methodologies included radio telemetry to address the questions (one and two) of salmon disposition and accountability while stock identification techniques were used to address the question regarding stock composition.

We arranged this annual report into two self-contained chapters entitled:

1) Upstream Passage and Spawning of Fall Chinook Salmon in the Snake River

2) Stock Identification of Snake River Fall Chinook Salmon