The Labrador Current cold front shaping the Atlantic salmon homing migration routes from the waters off Southern Greenland to eastern North America
Bibliographic record
Abstract
• Individual-based model simulates the homing migration of sub-adult Atlantic salmon. • Cold water front formed by Labrador Current deflects migrating salmon trajectories. • A breach in the thermal front favors the emergence of a secondary migration route. • The 1 °C isotherm bounds the thermal distribution of North American Atlantic salmon. Atlantic salmon ( Salmo salar ) experienced drastic population declines from the mid-1970 s to the early 1990′s throughout their range. The survival of the salmon while at sea is considered as the main driver of these declines, even though the underlying mechanisms are poorly understood. This study aims at improving the general understanding of the ocean distribution and migration timing of sub-adult salmon returning to North America from the waters off southern Greenland that could help determine the drivers of marine mortality. We used animal biotelemetry and numerical modeling to improve our knowledge of Atlantic salmon migratory behavior. We used data from 43 North American Atlantic salmon tagged at West Greenland, of which 5 individuals migrated towards their native rivers, and developed an individual-based model to simulate homing migration from their feeding grounds in South Greenland towards the coastal areas of their native rivers. The tagged and simulated salmon exhibited similar behavior when they encountered the cold water front formed by the southward flowing Labrador Current. The salmon either crossed the Labrador Current near the Newfoundland shelf break or continued their route southward along the warmer side of the cold front. These two pathways emerged as the migration routes split where the shelf slope is less steep. This discontinuity along the shelf break leads to a highly dynamic region, a high sea surface temperature variability, and occasional breaches in the thermal front that favor on-shelf fish migration. The salmon trajectories appear to be deflected when the front temperature is 1 °C or less. The 1 °C isotherm would thus bound the thermal distribution of North American Atlantic salmon and shape the species migration routes.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".