Cardiorespiratory physiology and temperature tolerance among populations of sockeye salmon (Oncorhynchus nerka)
Bibliographic record
Abstract
Elevated summer water temperature has been associated with high mortality in adult sockeye salmon (Oncorhynchus nerka) during their once-in-a-lifetime migration up the Fraser River (British Columbia, Canada) to their spawning grounds. There are over 100 genetically distinct populations of sockeye salmon in the Fraser River watershed, varying in migration distance, elevation gain, river temperature and river flow. This thesis studied the physiological basis for temperature tolerance in sockeye salmon and examined the overall hypothesis that each sockeye salmon population has physiologically adapted to meet their specific upriver migration conditions. Swimming and cardiorespiratory performance were compared over a range of temperatures across six wild, migrating adult sockeye salmon populations. All populations maintained maximum performance across the entire range of temperatures typically encountered during their upriver migration, with Chilko sockeye salmon emerging as the most high temperature-tolerant. In addition, populations with more challenging migrations had greater aerobic scope, larger hearts and improved coronary supply. These results suggest that sockeye salmon populations have physiologically adapted to cope with their local upriver migration conditions, despite never before having performed the upriver migration. Temperatures exceeding the population-specific thermal optimum resulted in severely impaired aerobic scope and swimming performance. This study suggests that population-specific thermal limits are set by physiological limitations in aerobic performance. Specifically, fish may be unable to swim at warm temperature due to insufficient oxygen supply to meet demand, triggered via a cardiac limitation due to reduced scope for heart rate. Given the key role of the heart in limiting thermal tolerance, the role of cardiac adrenergic stimulation was examined as a potential mechanism underlying the observed differences in thermal tolerance across sockeye salmon populations. Chilko sockeye salmon had a greater density of ventricular β-adrenoceptors, which may provide greater cardiac capacity and protection at temperature extremes, thereby expanding their breadth of thermal tolerance compared to other populations. This thesis suggests that sockeye salmon populations will be differentially affected by warming river temperatures, raising conservation concerns for biodiversity. This work provides important insight into local adaptation in sockeye salmon and identifies a possible cause for in-river mortality associated with warm temperatures in sockeye salmon.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 0.000 |
| 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".