Marked genetic structuring in localised spawning populations of cod Gadus morhua in the North Sea and adjoining waters, as revealed by microsatellites
Bibliographic record
Abstract
Previous studies of cod Gadus morhua population structure in European continental waters using molecular genetic markers have indicated high dispersal and limited structuring, in contrast to many tagging studies. More sensitive genetic techniques, in the form of microsatellite analysis, were used to reanalyse the population structure through the specific targeting of mature fish on spawning grounds. Significantly greater levels of differentiation were found than in previous studies, supporting the presence of 4 genetically distinct populations within the North Sea: Bergen Bank, Moray Firth, Flamborough Head and Southern Bight. Gene flow between the southern North Sea and eastern English Channel is largely restricted to populations within the Southern Bight (southern North Sea) and Beachy Head (eastern English Channel). The spawning stock in the central English Channel (Start Point) remains distinct from those in the Celtic Sea, Outer Hebrides, and central and northern North Sea. No evidence of sub-structuring within the Irish and Celtic Seas was found, in contrast to previous genetic studies, although the populations remained divergent from that of the Outer Hebrides. All European populations were significantly divergent from Canadian Scotian Shelf and Barents Sea (Bear Island) populations. The study indicates that the current fishery monitoring systems may need to be reassessed, particularly with respect to the North Sea, and highlights the value of using microsatellites combined with the targeting of spawning stocks to investigate subtle population structuring.
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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 | 0.001 |
| 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) | 0.000 | 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".