Estimation of Mid-Columbia Summer Chinook Salmon Escapement and Age Composition using PIT tags in 2006
A total of 633 summer Chinook salmon were PIT tagged at Bonneville Dam and tracked upstream between June 16 and July 26, 2006 using the PIT tag detection array system at mainstem dam fish ladders. Seventeen previously PIT tagged summer Chinook salmon were added to our sample. An additional 99 fall Chinook salmon were PIT tagged between September 8 and September 22, 2006. Based on PIT tagged recoveries, 75.3% of summer Chinook salmon passed upstream of McNary Dam, 69.3% upstream of Rock Island Dam, 33.3% upstream of Wells Dam, and 4.5% upstream of Lower Granite. Over the three weeks of fall Chinook salmon tagging, 47.5% of those fish tagged passed McNary Dam, 5.1% passed Ice Harbor Dam, and 1.0% passed Rock Island Dam. Summer Chinook salmon averaged 37.4 km/day between Bonneville and McNary dams while fall Chinook salmon averaged 39.1 km/day. No significant relationship was found between flow or water temperature and migration rate. Age composition estimates, based on scale pattern analysis, indicate that those summer Chinook salmon passing upstream of Ice Harbor Dam are predominantly yearling outmigrants (68.2% Age 1.2 and 24.2% Age 1.1), while those passing upstream of Rock Island Dam are a mixture of subyearling and yearling outmigrants (36.1% Age 0.4, 20.6% Age 1.3, 19.8% Age 0.3, and 9.2% 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 13.0 to 44.8% more fish at McNary and mid-Columbia dams than visual fish counts from mainstem dam fish ladders.
Fryer, J.K. 2007. Estimation of Mid-Columbia Summer Chinook Salmon Escapement and Age Composition using PIT tags in 2006. Columbia River Inter-Tribal Fish Commission Technical Report 07-02, Portland, Oregon. 40p.