Evidence for an ecological two-population model for white sharks (Carcharodon carcharias) in Australian waters
Bibliographic record
Abstract
Context Our understanding of population- and ecosystem-level processes commonly considers conspecific individuals to be ecologically equivalent. However, individuals of the same species may use resources differently, supporting the prevalence of individual specialisation or ‘apparent specialisation’. Individuals within a geographically defined population may also exhibit complex subpopulation movements, whereby individuals show philopatry to specific regions that further drives individual variation. Aims White sharks (Carcharodon carcharias) are top predators in temperate to tropical ecosystems. In Australia, two discrete subpopulations of white sharks (an east and a southwest subpopulation) have been proposed based on genetics and limited movement across Bass Strait. We aimed to characterise the extent of ontogenetic divergence in resource–habitat behaviour of white sharks from both regions. Methods We used high-resolution retrospective stable isotope profiles (δ15N and δ13C) of 74 white shark vertebral centra to examine ontogenetic trophic–habitat signatures for individuals sampled from both regions. Key results Our results demonstrate isotopic separation between juvenile–subadult sharks sampled east (−13.7 ± 0.72 δ13C; 14.2 ± 0.8 δ15N, n = 47) and southwest (−14.4 ± 0.6 δ13C; 12.5 ± 1.2 δ15N, n = 27) of Bass Strait, but with strong oscillatory trends across both regions, likely related to seasonal movements. Relative individual niche width revealed apparent specialised behaviour of juvenile–subadult sharks within both regions. Conclusions Retrospective ontogenetic isotopic profiles of vertebrae from Australian white sharks provide evidence to support an ecological two-population model for juvenile and subadult life stages. Implications Given many marine top predators are undergoing systematic population declines, understanding individual variation in diet and movement in the context of population structure and true or apparent specialisation is central to elucidating their ecological roles.
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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 | 0.003 | 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 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".