Estimation of Mid-Columbia Summer Chinook Salmon Escapement and Age Composition Using PIT Tags in 2007
In 2007, a total of 470 summer Chinook salmon (Oncorhynchus tshawytscha) were PIT tagged at Bonneville Dam between June 16 and July 13. An additional 763 spring Chinook salmon were PIT tagged between April 24 and June 15, while 194 fall Chinook were PIT tagged between September 13 and October 12. After adding previously tagged fish, and subtracting fish that likely shed PIT tags, a total of 764 spring Chinook, 470 summer Chinook, and 194 fall Chinook were tracked upstream. Between Bonneville and McNary dams, spring Chinook averaged 39.6 km/day, summer Chinook 39.8 km/day and fall Chinook 34.0 km/day. There was not a significant linear relationship between flow or water temperature and summer Chinook salmon migration rate downstream of McNary dam. However, there was a significant relationship between flow and water temperature and summer Chinook salmon migration rates upstream of McNary Dam. Age composition estimates, based on scale pattern analysis, indicate that those summer Chinook salmon passing upstream of Ice Harbor Dam are predominantly yearling outmigrants (70.9% Age 1.1 and 18.4% Age 1.2), while those passing upstream of Rock Island Dam are a mixture of subyearling and yearling outmigrants (26.7% Age 1.1, 21.7% Age 1.3, 16.3% Age 0.4, and 12.5% Age 1.2 with smaller percentages from other age classes). Mark-recapture techniques were used to estimate summer Chinook salmon abundance at upstream dams. These techniques estimated from 21.9% less to 6.5% more fish at McNary and mid-Columbia dams than visual fish counts from mainstem dam fish ladders.
Fryer, J.K. 2008. Estimation of Mid-Columbia Summer Chinook Salmon Escapement and Age Composition using PIT tags in 2007. Columbia River Inter-Tribal Fish Commission Technical Report 08-01, Portland, Oregon. 45p.