Identifying Hatchery and Naturally Spawning Stocks of Columbia Basin Summer Chinook Salmon Using Scale Pattern Analyses in 1990
Scales were sampled from Columbia Basin summer Chinook Salmon from different Snake and Mid-Columbia basin tributaries. Spring, summer, and fall Chinook Salmon races were also sampled at Bonneville Dam on the lower Columbia River. The age composition for each sample group was estimated. We found that both hatchery and natural origin Mid-Columbia Basin summer Chinook stocks included significant proportions of yearling and subyearling juvenile outmigrants. Snake Basin summer Chinook were composed entirely of yearling juvenile outmigrants. Scale pattern analysis (SPA) was used both to identify hatchery and natural origin stocks of summer Chinook Salmon from the Snake and Mid-Columbia basins, as well as to identify the different Columbia Basin Chinook Salmon races. A linear discriminant analysis procedure was used that indicated hatchery and natural origin summer Chinook Salmon stocks could be identified with a minimum accuracy of 72%. Pooled stocks of Snake and Mid-Columbia basin salmon were identified with a minimum accuracy of 81%. Relatively high classification accuracies (76-91%) were achieved identifying spring and summer Chinook Salmon races but classification of summer and fall Chinook Salmon races resulted in lower classification accuracies (59%). A sample of Age 1.2 summer Chinook Salmon collected at Bonneville Dam was estimated to be 86% hatchery origin and 14% natural origin. The same sample was estimated to be 72% Snake Basin origin and 28% Mid-Columbia origin. A mixed stock sample collected in the Snake Basin at the South Fork Salmon Weir was estimated to be 69% hatchery origin and 31% natural origin.
Fryer, J.K. and M. Schwartzberg. 1993. Identifying hatchery and naturally spawning stocks of Columbia Basin summer Chinook Salmon using scale pattern analyses in 1990. Columbia River Inter-Tribal Fish Commission Technical Report 93-4. Portland, OR. 42p.