The Use of Stable Oxygen Isotope (δ18O) Composition in Sockeye Salmon Body Fluid to Determine whether a Fish Has Been Caught in Freshwater
Bibliographic record
Abstract
Abstract Fisheries enforcement is often tasked with determining whether a seized Pacific salmon Oncorhynchus spp. has been caught legally or illegally, either in freshwater while it was migrating to its natal stream or in the ocean at some point during its life cycle or migration. Here we show that the oxygen stable isotope composition (δ18O) of the water within seized fish tissue, together with DNA analysis, provides a powerful means of establishing where the fish was migrating and whether it was inhabiting freshwater when harvested. These tools are relatively easy to apply and are supported by an extensive set of microsatellite DNA data for sockeye salmon O. nerka that provide “forensic” identification and by a time series record for δ18O in the water of the Fraser River. The difference between δ18O composition in the river (∼−17‰) and the ocean (∼−2‰), together with conservative mixing between the end members, provides wide discriminatory power. Evaporation or sublimation during storage favors the light isotope and would thus be to the advantage of the defendant.
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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 | 0.001 | 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".