Upstream passage problems for wild Atlantic salmon (Salmo salar L.) in a regulated river and its effect on the population
Why this work is in the frame
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Bibliographic record
Abstract
Due to hydropower development, the upstream migration of wild anadromous salmon and brown trout is impaired in many European rivers, causing negative effects on the long-term survival of natural salmonid populations. This study identified problems for Atlantic salmon during upstream migration in a regulated river in northern Sweden, Umeälven (mean flow: 430 m 3 s −1 ). Tagging from 1995 to 2005 involved radio tags ( n = 503), PIT tags ( n = 1574) and Carlin tags ( n = 573) to study the spawning migration of salmon from the coast past the regulated section of the river to a fish ladder at the dam/spillway 32 km upriver. The results demonstrate that migration success from the coast to the fish ladder varied between 0% and 47% among years, indicating an average loss of 70% of potential spawners. Discharge from the turbines attracted the salmon away from the bypass route. Echo-sounding in the turbine outlet showed that salmon were normally found at 1–4 m depths. They responded with upstream and/or downstream movements depending on flow changes; increased spill in the bypass channel attracted salmon to the bypass. Once in the bypass channel, salmon could be delayed and had difficulties passing the first rapid at high spills. Additional hindrances to upstream migration were found at rapids and the area of the fish ladder, located further upstream in the regulated river section. The average migration duration was 44 days from the estuary to the top of the fish ladder, with large variation among individuals within years. Modelling the salmon population dynamics showed a potential population increase of 500% in 10 years if the overall migration success could be improved from the current 30% to levels near 75%. Consequently improved migration facilities at the regulated river section should be implemented to achieve a long-term sustainability of these threatened anadromous salmonids.
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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 | 0.000 | 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 | 0.000 |
| 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 it