A10. Flottang

From PRAGMO
Jump to navigation Jump to search

This page has not been reviewed by an expert in this field. If you would like to contribute, please email RRC.

>> Back to Fisheries Surveys <<

1. Objectives[edit]

  • Monitoring of young eels (<15cm) upstream movement (Schaal, 2014)
  • Monitoring the recruitment of young eels in marshland not suitable for electrofishing (due to salinity or depth) (Chenal, 2017)
  • Identify migration routes and colonization fronts of young eels, and migratory obstacles
  • Measure ecological continuity after weir removal
  • Supplement data on young eels as electrofishing is not possible on small eels (<15cm)

2. Method summary[edit]

The equipment was developed by the “Cellule migrateurs Charente-Seudre” * in 2014. All the explanations below are from several years of testing.

The flottang is an assemblage of 10 50*50 cm layers of aerated geotextile (macmat) (CMCS, 2015) which shelters young eels (<15cm) during day, when they are least active. The gear floats near the surface and is attached to a stake by a rope. No bait is needed and eels can freely come and go. Once a week, during the morning, the device is netted and eels collected and counted. Previous studies suggest that the device has to stay in the water for at least 15 days before the study.

Although the device is new, it has proven to be efficient in studies (CMCS, 2015, 2018; Chenal, 2017; Perrault, 2019)

*Cellule Migrateurs Charente-Seudre : partnership between Etablissement Public de Bassin Charente (EPTB Charente), le Centre Régional d'Expérimentation Aquacoles (CREAA) and the association « Migrateurs Garonne Dordogne Charente Seudre » (MIGADO).

3. Advantages[edit]

  • Very cheap
  • Easy to use and clean
  • Little manpower required (one person)
  • Targets only < 15cm eels
  • Can be used in deep water and with different salinity
  • Can be set in environments where electrofishing is impossible (in branches, deep water, etc…)

4. Disadvantages[edit]

  • Limited background studies
  • Not currently used in England

5. Recommendation for method application[edit]

  • The traps have to be submerged in water for at least 1 week before its first use, so they lose their plastic smell. This smell can deter eels from the trap (Baisez, 2001)
  • Floats can be used to keep the device at the surface, depending on the environment and device buoyancy
  • The device has to be netted quickly to stop eels from escaping
  • Information labels are recommended so that the public do not remove the device. It could look like a rubbish in the water
  • Avoid non suitable habitats for young eels to get better results
  • Flottang location, their number per site and the frequency of sampling visits depend on the study objectives

6. Cost[edit]

Less than €10 per flottang. Additional costs are incurred due to the length of study and manpower.

7. Protocol and data analysis[edit]

As the method is new, current analysis is related to sampling effort, eel occupancy, or eel numbers per site, day, or year can be correlated with environmental variables (tidal coefficiency, daylength, lunar cycle, season, environment type, and population structure). Examples can be found in the bibliography and will provide some guidance for analysis (in French).

See References for protocol examples.

8. Acknowledgement and associated authors[edit]

Audrey Postic-Puivif. EPTB Charente / Cellule Migrateurs Charente-Seudre

9. References[edit]

  1. Chenal A., (2017) Élaboration d’un protocole de suivi des civelles pour deux Marais Vendéens. Mémoire de dominante d'approfondissement Gestion des Milieux Naturels. LOGRAMI. 69 pages.
  2. CELLULE MIGRATEURS CHARENTE SEUDRE, Rapport des actions 2015. EPTB Charente, Groupement des fédérations de pêche du Poitou-Charentes, CREAA. Programme d’actions 2012-2015 pour la sauvegarde et la restauration des poissons migrateurs amphihalins sur les bassins Charente et Seudre.11 pages.
  3. CELLULE MIGRATEURS CHARENTE SEUDRE, Rapport des actions 2016. EPTB Charente, Groupement des fédérations de pêche du Poitou-Charentes, CREAA. Programme d’actions 2016-2020 pour la sauvegarde et la restauration des poissons migrateurs amphihalins sur les bassins Charente et Seudre.126 pages.
  4. CELLULE MIGRATEURS CHARENTE SEUDRE, Rapport des actions 2018. EPTB Charente, Groupement des fédérations de pêche du Poitou-Charentes, MIGADO, CREAA. Programme d’actions 2016-2020 pour la sauvegarde et la restauration des poissons migrateurs amphihalins sur les bassins Charente et Seudre.86 pages. Juin 2019.
  5. PERRAULT A., (2019). Suivi de la colonisation 2019 des anguilles sur la Charente et la Seudre.Rapport de stage Master 2 Gestion de l’environnement et des milieux aquatiques – Université d’Aix Marseille. MIGADO - Cellule Migrateurs Charente Seudre. 51p.
  6. BAISEZ A., (2001) « Optimisation des suivis des indices d’abondances et des structures de taille de l’anguille européenne (Anguilla anguilla, L.) dans un marais endigué de la côte atlantique : relations espèce - habitat ». Toulouse : Université de Toulouse III - Paul Sabatier.
  7. SCHAAL A., (2014). Colonisation de l’anguille : recherche et mise en place d’une méthode de suivi par piégeage sur le bassin Charente. Rapport de Master 2. Cellule Migrateurs Charente Seudre, Groupement des Fédérations de pêche du Poitou-Charentes. 43 p.
  8. https://www.migrateurs-loire.fr/habitats-artificiels-suivre-anguillettes-marais-vendeens/
  9. https://observatoire-poissons-migrateurs-bretagne.fr/actualites-2016/le-flottang-quesako
  10. http://www.migado.fr/dispositif-flottang-pour-le-suivi-des-anguilles/