Isotopic Tracers Suggest Limited Trans-Oceanic Movements and Regional Residency in North Pacific Blue Sharks (Prionace glauca)
Bibliographic record
Abstract
Blue sharks (Prionace glauca) are globally distributed, large-bodied pelagic sharks that make extensive migrations throughout their range. In the North Pacific, mark-recapture studies have showntrans-Pacific migrations, but knowledge gaps in migration frequency hinder understanding of regional connectivity and assessments of regional demography for stock assessments. Here, we use oceanographic gradients of stable isotope ratios (i.e., regional isoscapes) to determine exchange rates of blue sharks between the East and West North Pacific Ocean (EPO and WPO). We generated regional δ13C and δ15N distributions for blue sharks from published values in the North Pacific (n= 180; both sexes, juveniles and adults combined). Discriminant analysis suggested lowtrans-Pacific exchange, categorizing all western (100%) and most eastern (95.3%) blue sharks as resident to their sampling region, with isotopic niche overlap of WPO and EPO highly distinct (0.01–5.6% overlap). Limitedtrans-Pacific movements suggest that other mechanisms maintain genetic mixing of the North Pacific blue shark population. Potential finer scale movement structure was indicated by isotopic differences in sub-regions of the eastern and western Pacific, though application of mixing models are currently limited by aberrantly low blue shark δ13C values across studies. Our results suggest that blue shark population dynamics may be effectively assessed on a regional basis (i.e., WPO and EPO). We recommend further studies to provide size- and sex-specific movement patterns based on empirical isotopic values with large sample sizes from targeted regions. Strategically applied stable isotope approaches can continue to elucidate migration dynamics of mobile marine predators, complementing traditional approaches to fisheries biology and ecology.
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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 | 0.000 |
| 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".