The Courter study authors indeed suggest that temporal and spatial separation may explain why they found a lack of impact on the natural-origin winter population. However, this separation was not dam-related. The Courter study focused only on the upper Clackamas Basin above N.F. Dam, and the study looked back to a time when hatchery summer steelhead were planted in the mainstem above the dam, and both hatchery summer steelhead and natural-origin winter steelhead were passed above the dam. Thus, my main reason for responding to Salmo g's post was to point out that the study's findings cannot be attributed to removal of hatchery summer runs at the dam. The temporal and spatial separation discussed by the authors is due to factors other than a physical barrier. One last thing, when the Courter authors indicate hatchery summer runs were planted in the lower mainstem Clackamas, I believe they are referring to the lower mainstem of the upper Basin, which is above the dams, as opposed to the mainstem below the dams.