Size, age composition, and upstream migration of American eels at the Millville Dam eel ladder, Shenandoah River, West Virginia
Bibliographic record
Abstract
Abundances of American eel (Anguilla rostrata) are declining along the east coast of the United States and Canada, possibly due to habitat loss and barriers to migration. In Atlantic coast watersheds, dams detain upstream migration of juveniles, and little is known about age class composition, age-length relationships, or environmental cues to upstream migration of yellow-phase eels. An eel ladder was installed on the Millville hydroelectric dam, lower Shenandoah River, WV, to facilitate and monitor the upstream movement of yellow phase eels. Daily length measurements (TL cm) and weights (g) were taken on eels using the ladder during three sampling periods; spring/summer 2004 (May 14-July 23), fall 2004 (Sept 10-30), and spring/summer 2005 (June 1-July 31). Additionally, otolith-based ages were estimated from a subsample of eels. To examine environmental variables associated with upstream migration, candidate models were fit to daily count data and included combinations of four environmental covariates (barometric pressure, local precipitation, lunar illumination, and river flow) and a year effect. A total of 4,847 eels used the ladder during the three sampling periods. Eel sizes were similar among sampling periods (range 19-75 cm TL), and age estimates from 74 eels (21.4-55 cm TL) ranged from 3 to 10 years. Estimates of mean length at age of eels from Shenandoah River were low relative to published estimates from southern and northern latitudes. Peaks in eel counts coincided primarily with low levels of lunar illumination or with rise in river flow, and the data supported an additive model of lunar illumination and river flow. The data did not support single-variable or additive models with covariates of barometric pressure or local precipitation, or models with a year effect. Management strategies for American eels will benefit from short and long-term studies of eel ladders, including additional focus on eel counts, size and age composition, and upstream migration.
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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 | 0.001 |
| 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) | 0.001 | 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 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".