Resistance of the size structure of the fish community to ecological perturbations in a large river ecosystem
Bibliographic record
Abstract
Summary Frequency distributions of log‐scaled abundance and body size for aquatic biota, including fish, yield size spectra that provide gross estimates of food‐web capacity (number of individuals supported by the food web indexed by the midpoint height or y ‐intercept) and ecological efficiency (rate of decreasing organismal abundance with increasing body size as indicated by the size‐spectra slope). Size spectra are known to respond in predictable fashion to exploitation by commercial (marine) fisheries, but there has been relatively little research of size spectra in freshwater systems and less evaluation of how community size‐structure responds to the wider array of ecological perturbations prevalent in freshwater systems. We used a 29‐year experimental gillnet data set to test the responses of food‐web capacity and ecological efficiency (as indexed by size spectra) of a large river fish community to variations in predatory demand (population expansion of double‐crested cormorant, P halacrocorax auritus ) and perturbations affecting primary production (reductions in total phosphorus and warming summer water temperature). Fish community capacity (size‐spectra elevation) and ecological efficiency (size‐spectra slope) showed low interannual variation (coefficients of variation 5.6 and 15.4%, respectively). Though highly stable, food‐web capacity decreased over time concurrent with declining total phosphorus concentrations and increasing cormorant abundance. Interannual variation in ecological efficiency was not related to the measured perturbations. Relative abundance of the core species that comprised 95% of the community remained relatively consistent over time. The fish community size‐structure was also stable and resistant to ecological perturbation. However, we found measurable changes in the composition of secondary species, and these were associated with an increase in cormorant abundance and decrease in total phosphorus. The lack of change in core community species representation and in overall size structure suggest community‐level compensatory mechanisms were operating.
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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) | 0.000 | 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 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".