Water temperature gave no repeated linear decrease in dam-to-dam conversion of PIT-tagged adult salmon in the Columbia Basin in 2004-2025; lower conversion at 22 C or more came mostly from 2015
Question: does warm river water during the upstream migration decrease the probability that a PIT-tagged adult salmon reaches the next dam? We used 153,308 fish-reach records (86,813 fish-years) from Columbia River DART for seven stock groups (upper Columbia and Snake sockeye, spring, summer and fall Chinook) in three reaches, 2004-2025. We joined each fish to the mean dam water temperature in its passage window. The planned main model compared fish of the same stock, reach and year, with a common seasonal curve, and used year-bootstrap intervals. We wrote the plan before the fits and tested 2004-2014 and 2015-2025 separately. The pooled change in log odds of conversion per +1 C was +0.039 (95% CI -0.022 to +0.110) in 2004-2014 and -0.092 (-0.230 to +0.108) in 2015-2025. Only 7 of 14 stock-reach slopes had the same sign in both periods. A model fitted on 2004-2014 predicted 2015-2025 outcomes slightly worse with temperature than without it (skill -0.005, CI -0.011 to -0.000). In pooled bin models, fish at 22 C or more had log odds of conversion 0.99 lower than fish at 16-18 C in 2015-2025 (CI -1.36 to -0.13). Without 2015 this contrast was -0.29, so it depends mostly on one year. Converted fish moved faster in warmer water (log travel time -0.051 and -0.076 per C; 13 of 14 series negative), except Snake fall Chinook in the lower river, which moved more slowly. Limitations: year effects leave only 0.2-0.6 C of temperature variation; conversion includes harvest, straying and detection loss as well as death; most tagged fish are hatchery fish; one river basin; correlational design.
salmon · Chinook salmon · sockeye salmon · PIT tag · upstream migration · river temperature · thermal stress · heat extremes · 2015 heat · Columbia River · Snake River · conversion rate · travel time · observation bias · replication · out-of-period test · climate change
References
6- useshttps://www.cbr.washington.edu/dart/query/pitadult_conrate
Source of the per-fish PIT-tag adult detection records (PIT-tag data from PSMFC PTAGIS).
- useshttps://www.cbr.washington.edu/dart/query/adult_daily
Source of daily dam water temperatures.
- useshttps://www.ptagis.org
Original PIT-tag information system of the Pacific States Marine Fisheries Commission that supplies the DART records.
- reviewsdoi:10.1111/j.1600-0633.2007.00267.x
Reports temperature-related en route mortality of Snake River sockeye; we test a related effect with PIT-tag conversion of seven stock groups.
- supportsdoi:10.1577/T04-113.1
Reports slowed migration and use of cool water by adult fall Chinook in warm water; our fall Chinook travel-time slope agrees.
- Shad passage at Columbia River dams stopped advancing after about 1988 while river temperature increased, and 1950-1993 temperature slopes did not hold in 1994-2025 sci:sha256:8aa8a8f194d985b46635b07223b7dcb0fcd38e752d6112fb1301c1db9cbc5bdd
Campaign study of shad and sockeye passage timing with the same DART dam counts and temperatures; context for the river temperature record.
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