Conséquences de l'artificialisation de l'hydrologie du Rhône sur la structuration des communautés d'invertébrés et de poissons - Rapport final
Bibliographic record
Abstract
The aim of action no. 15 of the Cemagref - Agence de l'Eau RM&C framework agreement was to assess the impact of major fluctuations in the flow of the Rhône on communities of fish and benthic macroinvertebrates in the Sault-Brénaz - Jons section over the period 2008 - 2009. The present report is an account of the work carried out over these two years. The different parts of this work are : (1) a presentation of the study section, with particular emphasis on the hydrological regime; (2) a two-dimensional hydrodynamic model of the study area; (3) a functional approach to the variability of fish habitat conditions; (4) an analysis of the spatial distribution of invertebrates along an exondation gradient linked to flow variations; (5) a qualitative description of the structure of the fish community, complementing the seasonal monitoring carried out by Cemagref; (6) a description of fish and invertebrate habitat conditions; (7) an analysis of some probable negative effects linked to the observed flow variations, and (8) a conclusion.Hydrodynamic modelling makes it possible to determine the hydraulic conditions prevailing in the section at any given point and over the entire range of flows observable in the section (150 - 1000 m³.s-1), and to translate these conditions into available habitat for fish and invertebrates. The methodology developed on the Seine to produce vital habitat maps is transferable to the Rhône, where the physical variables are available thanks to hydrodynamic modelling. The effect of flow fluctuations is significant on the availability of vital habitats (spawning, feeding & resting) for the species studied (barbel, hotu, chub and spirlin). Sampling of benthic invertebrates revealed a spatial distribution of species graded from the edge of the wetted bed to the foot of the bank according to the dewatering gradient. In the channel, a flow variation of 200 m³.s-1 alters the width of the wetted bed and the surface area of potential hydraulic habitats available to benthic invertebrates. For fish, given the habitat models available, the analysis of the probable effect of variability in habitat availability on the structuring of the fish community needs to be completed. New knowledge needs to be acquired in order to gain a more precise understanding of fish behaviour during hydropeaking-type flow variations. Net fishing represents a complementary alternative to electrofishing for describing the structure of the fish community in the section of the Rhône under study, even though flow fluctuations are very restrictive for this type of fishing gear. In particular, it allows the capture of large individuals (potential spawners) that move around a lot, and probably in the channel, or live in deep areas (> 2m), making it impossible to capture them electrically.The main conclusion of this work is that 1) the intensity, speed and frequency of flow fluctuations are unfavorable to fish and benthic macroinvertebrate communities in the section studied, and 2) that a minimum base flow (between 200 and 300 m3.s-1; for the moment it is difficult to be more precise) could reduce these effects.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".