Sulfur stable isotopes as a tracer of insect migration and consumption by fish predators
Bibliographic record
Abstract
Resource flows between freshwater ecosystems can greatly affect foodweb dynamics. The seasonal movement of a family of aquatic insects, water boatmen, or corixids (Hemiptera: Corixidae) represents an important transfer of resources between wetland and river ecosystems. Corixids migrate en masse from wetlands in the North American prairies to rivers every autumn to overwinter. In the North and South Saskatchewan rivers, Saskatchewan, Canada, several fish species prey upon these migratory corixids. Here, we examined the utility of the stable isotope ratio of sulfur, δ34S, in tracing the migration of corixids between wetlands and the North and South Saskatchewan rivers. We also assessed the extent to which riverine fish use migratory corixids as a dietary subsidy. We found that both corixids and other wetland invertebrates exhibited a mean δ34S value of −10.5 ± 5.8‰, lower than riverine invertebrates at −4.1 ± 4.1‰. Specifically, riverine invertebrates from the South Saskatchewan River were more depleted in 34S than those from the North Saskatchewan River, with means of −5.1 ± 4.1‰ and −1.4 ± 2.8‰, respectively. In summer, corixid-feeing and noncorixid-feeding fish exhibited similar δ34S values in liver tissue, whereas in spring and autumn, corixid feeders exhibited more negative δ34S values. Isotope mixing models indicated that corixid-feeding species may have derived 34 to 65% of liver tissue from wetland sources in spring, 15 to 34% in summer, and 41 to 78% in autumn, whereas contributions to noncorixid-feeding species ranged from 4 to 17% across all seasons. We conclude that δ34S has the potential to trace insect movement and consumer use between isotopically distinct freshwater systems.
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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 | 0.001 | 0.001 |
| 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".