Ontogenetic shifts in isotope-inferred trophic ecology of Atlantic bluefin tuna Thunnus thynnus in Atlantic Canada
Bibliographic record
Abstract
Upper trophic level predators can greatly influence the dynamics and productivity of forage fish species. Quantifying this influence requires information on prey consumption; however, establishing feeding habits of highly mobile predators is particularly challenging. Stable isotopes of carbon and nitrogen (δ 13 C and δ 15 N) have been applied to characterize the trophic ecology of Atlantic bluefin tuna Thunnus thynnus (ABFT) in several important regions; however, applications in Canada are lacking. Here, we used δ 13 C and δ 15 N values of ABFT muscle tissue collected in 2014-2018 on 2 important foraging grounds along the coast of Atlantic Canada to evaluate the temporally integrated trophic ecology of this ecologically and commercially important species. Populations of some small pelagic fish species in these areas have been depleted, and predation by ABFT is considered a potentially important contributor. Isotopic diet reconstructions found that Atlantic mackerel were the dominant prey in the southern Gulf of St. Lawrence, and a combination of Atlantic herring and sandlance were the most dominant prey consumed on the Scotian Shelf. Diet reconstructions identified an ontogenetic shift in prey consumption, with more sandlance consumed by smaller ABFT and a shift to higher consumption of Atlantic mackerel and Atlantic herring as fish increased in size. Isotopic niche overlap indicated relatively high overlap for adults among years, suggesting that ABFT did not show substantial inter-annual variation in their trophic ecology. Overall, the study provides insight into the trophic ecology of ABFT along the Atlantic Coast of Canada that can be integrated into investigations of predator impacts on depleted mackerel and herring populations.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".