Decoupling outmigration from marine survival indicates outsized influence of streamflow on cohort success for California’s Chinook salmon populations
Bibliographic record
Abstract
Historically, marine survival estimates for salmon have been confounded with freshwater seaward migration (outmigration) survival. Telemetry studies have revealed low and variable survival during outmigration, suggesting marine mortality may not be the primary source of variability in cohort size as previously believed. Using a novel combination of tagging technologies, survival during these two life stages was decoupled over 5 years for Sacramento River Chinook salmon (Oncorhynchus tshawytscha). Outmigration survival ranged from 2.6% to 17%, and marine survival ranged from 4.2% to 22.8%. Influential environmental drivers in both life stages were also compared with smolt-to-adult ratios (SAR) for three Chinook salmon populations over 20 years. Streamflow during outmigration had higher correlation with SAR (r2 > 0.34) than two marine productivity indices (r2 < 0.08). The few SAR estimates that were poorly predicted by flow occurred during years with the lowest marine productivity, suggesting most interannual SAR fluctuations are explained by outmigration survival, but abnormally poor marine conditions also reduce SAR. The outsized influence of flow on SAR provides managers with a powerful mitigation tool in a watershed where flow is tightly regulated.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".