"March 1994"

Includes bibliographical references (leaves 17-20)

[SN 11550] App. D. Escapements and numbers of redds of summer/fall chinook salmon counted during aerial surveys on tributaries of the upper mid-Columbia River, Washington, 1956-1992. Escapement to the tributaries (ET) is peak aerial count times 3.1 fish/redd (from Meekin, 1967a). Wells count (WC) is the number of salmon passing over Wells Dam less Indian harvest. ET/WC is the quotient of escapement to the tributaries to counts at Wells Dam.

(1) We used both ground and aerial surveys to assess number and distribution of redds, and time of spawning of summer/fall chinook salmon in sampling reaches on the Methow, Okanogan, and Similkameen Rivers. (2) During ground surveys we counted 604 redds in tributaries upstream from Wells Dam: 154 in the Methow River, 162 in the Okanogan River, and 288 in the Similkameen River. (3) Peak aerial counts of redds were 53% to 89% of the total ground counts: 116 redds in the Methow River, 144 in the Okanogan River, and 152 in the Similkameen River. (4) Spawning began the third week of September on the Methow and Similkameen rivers, and the first week of October on the Okanogan River. Activity peaked the first week of October on the Similkameen River and the third week of October on the Methow and Okanogan rivers. (5) Spawning progressed from higher to lower elevations on the Methow and Okanogan rivers. Redds were clumped on all rivers, but most widely dispersed on the Okanogan River. (6) We found 180 salmon carcasses in tributaries upstream from Wells Dam: 65 (of which 48% were female) in the Methow River, 41 (49% female) in the Okanogan River, and 74 (35% female) in the Similkameen River. (7) Females in the Methow River voided 80-100% (mean=99.05%) of their eggs, females in the Okanogan spawned 84-100% (mean=99.18%) of their eggs, and females in the Similkameen River voided 99-100% (mean=99.92%) of their eggs.