Submitted to Transactions of the North American Fisheries Society
Abstract
We show that salmon migration swim speed increases with temperature, to an optimal, and then diminishes at higher temperatures, in an examination of data from 5226 adult chinook salmon, PIT-tagged as juveniles, migrating up the Columbia and Snake rivers from Bonneville Dam to Lower Granite Dam, a distance of 462 km encompassing passage of seven dams. Because the migration duration ranged from seven to 130 days, we developed a new analysis method, based on swim speed-ranked data partitioning, which extricates both delay times and swim speeds from migration time data. The resulting broken linear model for the swim speed/temperature relationship provides a better alternative to the currently accepted exponential form, which overestimates speeds at higher temperatures. The warming effects of dam impoundments and global climate change make modeling of higher temperatures particularly important, especially given that migration time has a bioenergetic impact on spawning success.