Spatial and temporal gradients in artisanal fisheries of a large Neotropical reservoir, the Itaipu Reservoir, Brazil
Why this work is in the frame
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Bibliographic record
Abstract
Physical, chemical, and biological gradients along reservoirs are clear and exhibit marked spatial and temporal variations. These variations are rarely quantified and may produce spatial gradients in fisheries. We analyzed trends in total yield and gradients and relationships between catch-per-unit-effort (CPUE) and some characteristics of the fishery in the large Neotropical Itaipu Reservoir in Brazil. Data on the artisanal fisheries were collected over an 11-year period (414 213 daily trips). Annual yield (especially after 1993) and CPUE (annual total and for each species) decreased over the studied period. A clear longitudinal pattern in the CPUE values for the main species was recognized, and this pattern presented a significant relationship with the type of gear and characteristics of the vessels used in the fisheries. The decline in yield and CPUE is apparently due to changes in trophic state, as well as to the construction of reservoirs upstream from the region and to overfishing. It is clear that the spatial zonation influenced fish species distribution along the reservoir and, therefore, the fishery. We conclude that for this large Neotropical reservoir, spatial gradient cannot be ignored in management plans, and this appears to be true for any reservoir that exhibits zonation.
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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 | 0.001 | 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 | 0.003 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 it