"June 1993"

Includes bibliographical references (p. 16-17)

INTRODUCTION: Hundreds of thousands of chum returned to the Columbia River less than a century ago. In 1929, commercial landings peaked at nearly 700,000 fish (Chaney and Perry, 1976). As recently as 1942, nearly half a million Columbia River chum were landed by commercial fishermen. Sinc ethe early-1960's however, commercial catches have not exceeded two thousand fish (except 1988). In addition, peak fish/mile index area spawning ground counts have not exceeded one thousand fish (WDF, 1992). Oregon Columbia River chum escapement is currently so small the state has classified them as a "sensitive" species. In 1993, Washington's Grays River system and Hamilton Creek chum stock status were described as "depressed" (WDF, et al., 1993). Historically, chum were found in many Columbia River tributaries. Currently, there are a few tributaries that maintain low levels of chum production; however, the only remaining viable natural spawning populations are found in the Grays River system and Hamilton and Hardy creeks in Washington. This report will focus on the Grays River system natural spawning population. The Grays River was once noted for its large runs of chum salmon. In 1936, a total of 6,286 chum were counted below the falls at river mile 13 and an additional 1,388 chum were counted in the West Fork of the Grays River (Bryant, 1949). Today, the Grays River chum run is a fraction of the historic run size. Washington Department of Fisheries (WDF) records indicate chum spawned in the West Fork and mainstem Grays River, Seal River, and Malone, Fossil, Hull, Klints, and Carzy Johnson creeks (WDF, 1973). No spawning ground counts could be found for Seal River and Malone Creek though chum numbers are assumed to be minimal. Chum are no longer consistently observed in Fossil, Hull, and Klints creeks and those streams are usually not surveyed. The West Fork of the Grays River peak area index counts are usually minor but are part of the annual spawning ground counts. Crazy Johnson Creek and the mainstem Grays River comprise the remaining annual spawning ground counts. By 1978 it was apparent that production had shifted to the mainstem Grays and Crazy Johnson Creek; at least partially the result of spawning habitat degradation in other areas of the Grays River system (Dammers, 1979). A map of the Grays River chum spawning areas can be found in Figure 1. In 1985, WDF Habitat Division constructed a pilot spawning channel at Gorley Springs. Subsequent spawning ground counts revealed a substantial number of chum spawned in the improved channel. Over 400 0chum were counted in Gorley Creek the following year (Fiscus, 1987). Except for 1951, pre-1968 index area counts were enumerated as fish/mile. Washington Department of Fisheries estimated 7,500 chum returned to the Grays River system in 1951. In 1978, WDF conducted a carcass tagging experiment to determine the Grays River chum natural spawning population. For the purpose of that population estimate, Grays River chum were treated as one homogenous population. Grays River total spawning ground population estimates were calculated for 1968 - 1978 using this information (Dammers, 1979). However, peak expansion factors for each individual stream may be more accurate. During low flow years, chum spawn primarily in the larger mainstem Grays River; during higher flows they can be found in large numbers in the smaller tributaries. In addition, individual stream peak count expansion factors are assumed to be different based on stream size, length, and flows. By creating individual peak count and visibility expansion factors, it is possible to re-examine historical data where peak fish/mile counts and water visibility conditions were made and use this information to construct past total natural spawning population estimates. In addition, age composition data has been gathered for many years. By combining the population estimates with the age composition, return and brood year tables could be created; hence historical Grays River chum returns could be used to predict future runs. In 1991, chum carcasses were tagged to determine individual peak count and create visibility expansion factors. The index areas used in the 1978 study were repeated for the 1991 study. In addition, WDF attempted to conduct a carcass tagging study to estimate the total chum natural spawning population in Gorley Creek. Details of the carcass studies and attempts to create individual natural spawn population estimates (including Gorley Creek) and re-examination of past data to improve the historical data base are provided in this report.