This report summarizes results for the project “A Stock Assessment and Research Plan For Mid-Columbia River Summer Chinook, Parts I and II” (Southeast Sustainable Salmon Fund Project No.s 45060 and 45289). The project involved field work in 2004 and 2005 performed by the Columbia River Inter-Tribal Fish Commission (CRITFC), and the Yakama Nation (YN) Department of Fisheries. Activities were designed to describe characteristics of adult escapement, juvenile production and out-migration, and ocean migration of Mid-Columbia summer (summer/fall ocean-type) Chinook salmon Oncorhynchus tshawytscha in the Methow River, Okanogan County, Washington. Primary results were:

• Tower counting for adult escapement estimation was deemed unreliable for this river due to high frequency of turbid conditions.
• Collaboration with WDFW on a radio telemetry project involving tagging of returning adults at Wells Dam indicated that 12.5% of these fish migrated into the Methow River. Based on a total count of 34,075 at Wells dam in 2005, escapement of adult summer Chinook to the Methow River is estimated to have been 4,259 ± 1,320.
• Researchers also collaborated on another CRITFC project to test the capabilities of a long range model of a Dual Identification Sonar (DIDSON-LR). Results indicated that the instrument can yield accurate counts of migrating fish at a distance of 42m and more, though resolution of the images was insufficient to make more than qualitative estimates of fish size.
• Juvenile sampling with a rotary screw-trap from May to July indicated that smolt outmigration was 526,385 in 2004 and 504,908 in 2005. Peak migration occurred in the first or second week of June. Genetic analyses indicated that approximately 85% of the fish were summer Chinook, while 15% were spring Chinook. Correction for the latter percentage provides estimates of total summer Chinook production of 444,269 in 2004, and 433,312 in 2005. Although (subyearling) summer Chinook juveniles tended to be smaller than (yearling) spring Chinook, there was significant overlap in length between stocks.
• PIT tagging of a sample of outmigrating juveiles provided a geometric mean travel time of 31 days from the Methow River to to McNary Dam in both years. Survival to McNary Dam was only 7-8%.