MECHANISTIC BASIS OF INDIVIDUAL MORTALITY IN PACIFIC SALMON DURING SPAWNING MIGRATIONS
Bibliographic record
Abstract
Reproductive-based migration is a challenging period for many animals, but particularly for Pacific salmonids, which must navigate from the high seas to freshwater natal streams. For the first time, we attempt to answer the question as to why some migratory adult Pacific salmon die en route to spawning grounds. Summer-run sockeye salmon (Oncorhynchus nerka) were used as a model, and the migration behavior of 301 fish was followed by intercepting them in the ocean about 215 km from the mouth of the Fraser River, British Columbia, Canada, and implanting a gastric radio transmitter. Before release, telemetered fish were also bio-sampled, which included drawing a blood sample, collecting a gill biopsy, and quantifying energetic status with a microwave energy meter. We tested the predictions that the fish that died prematurely would be characterized by low energy reserves, advanced reproductive development, elevated indicators of stress, and low osmoregulatory preparedness compared with fish that completed their river migration. Just over half (52.3%) of the sockeye tagged were subsequently detected in the Fraser River. Salmon that failed to enter the river had exhibited indicators of stress (e.g., elevated plasma lactate, glucose, and cortisol). Contrary to our prediction, fish that failed to enter the river tended to have higher gross somatic energy and be larger at the time of sampling in the ocean than fish that successfully entered the river. Of the fish that were detected in the river (i.e., 134 fish excluding fishery removals), 9.7% did not migrate beyond the lower reaches (approximately 250 km from ocean), and a further 14.2% reached the upper reaches but failed to reach natal sub-watersheds, whereas the remainder (76.1%) reached natal sub-watersheds. Of these, fish unsuccessful in the lower reaches tended to have a high plasma osmolality in the ocean, whereas fish failing in the upper reaches had lower levels of reproductive hormones in the ocean.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 teacher head, 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".