Temperature and depth profiles of Chinook salmon and the energetic costs of their long-distance homing migrations.

摘要: Abstract River warming poses an existential threat to many Pacific salmon (Oncorhynchus spp) populations. However, temperature-mediated risks are often complex and addressing them requires species- population-specific data collected over large spatial temporal scales. In this study, we combined radiotelemetry with archival depth temperature sensors collect continuous thermal exposure histories of 21 adult spring- summer-run Chinook (O. tshawytscha) as they migrated hundreds kilometers upstream in the Columbia basin. Salmon impounded reaches Snake rivers were characterized by low daily variation but frequent extensive vertical movements. Dives associated slightly cooler body temperatures (~ 0.01 0.02 °C/m), there was no evidence for use cool-water refuges deep reservoirs or at tributary confluences along migration route. tributaries, constrained relatively shallow water, experienced ~ 2–5 °C diel fluctuations. Differences timing among route-specific regimes resulted substantial among-individual exposure. Bioenergetics models using swim speeds ranging from 1.0 1.5 body-lengths/s predicted median energetic costs ~ 24–40% (spring-run) ~ 37–60% (summer-run) initial reserves. Median declines total mass ~ 16–24% spring-run ~ 19–29% salmon. A simulated + 2 °C increase water 4.0% 6.3% more energy used per fish, on average. The biotelemetry provided remarkable resolution Nonetheless, information gaps remain development robust bioenergetics climate effects