John Day Basin Spring Chinook Salmon Escapement and Productivity Monitoring; Fish Research Project Oregon, 1999-2000 Annual Report.

Abstract

The John Day River basin supports one of the healthiest populations of spring chinook salmon (Oncorhynchus tshawytscha) in the entire Columbia River basin. Spring chinook salmon in this basin are therefore, used as an important index stock to measure the effects of future management actions on other salmon stocks in the Columbia basin. To meet the data requirements as an index stock, we estimated annual spawner escapement, age-structure, and smolt-to-adult survival. This information will allow us to estimate progeny-to-parent production for each brood year. To estimate smolt-to-adult survival rates, 1,852 chinook smolts were tagged with PIT tags from 3 March to 5 May, 2000. Length of captured smolts varied, ranging from 80 to 147 mm fork length (mean = 113 mm). These fish will be monitored for PIT tags as returning adults at dams and during future spawning ground surveys. During spawning ground surveys, a total of 351.3 km of stream were surveyed resulting in the observation of 478 redds. When expanded, we estimated total number of redds at 481 and total number of spawners at 1,583 fish in the John Day River basin. We estimated that 13% of the redds were in the mainstem John Day, 27% in the Middle Fork, 34% in the North Fork, and 26% were in the Granite Creek basin. Sampled carcasses had a sex ratio comprised of 53% females and 47% males with an age structure comprised of 0.5% age-2, 6.3% age-3, 88.7% age-4, and 4.5% age-5 fish. Five of the 405 carcasses examined had fin clips suggesting they were of hatchery origin. The 1999 index redd count total for the North Fork, Mainstem, and Granite Creek was lower than the 1999 average (535) but well within the range of annual redd counts during this period. The index redd count for the Middle Fork was higher than the 1990's average (92) but considerably lower than the average from 1978-1985 (401). Although quite variable over the past 40 years, the number of redds in the John Day River basin during 1999 was well within the range of redd counts since they were initiated in 1959.