Le marais doux endigué de Bourgneuf-Machecoul (Pays de Loire) Premier éléments de connaissance du peuplement piscicole. Relation ichtyofaune-habitat et problèmes majeurs de gestion (Maroc)
The dammed up marshes of the French Atlantic coast cover about 200 000 ha between River Vilaine and the « Bassin d'Arcachon ». Eighty eight % are managed with freshwater. They constitute original environments initially created for agriculture or for salt production, and they are now threatened...
| Published in: | Revue des sciences de l'eau |
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| Main Authors: | , , , |
| Format: | Article in Journal/Newspaper |
| Language: | French |
| Published: |
Université du Québec - INRS-Eau, Terre et Environnement (INRS-ETE)
2005
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| Subjects: | |
| Online Access: | http://www.erudit.org/fr/revues/rseau/1992-v5-n4-rseau3268/705144ar.pdf https://www.erudit.org/fr/revues/rseau/1992-v5-n4-rseau3268/705144ar.pdf https://id.erudit.org/iderudit/705144ar https://doi.org/10.7202/705144ar https://www.erudit.org/fr/revues/rseau/1992-v5-n4-rseau3268/705144ar/ https://core.ac.uk/display/59609542 https://academic.microsoft.com/#/detail/2165598010 |
| Summary: | The dammed up marshes of the French Atlantic coast cover about 200 000 ha between River Vilaine and the « Bassin d'Arcachon ». Eighty eight % are managed with freshwater. They constitute original environments initially created for agriculture or for salt production, and they are now threatened by land abandonment within the next decade. Concurrently to aquaculture (in created or existing ponds), exploitation of the fish stocks in the ditchweb is likely to encourage a diversification of agricultural activities. Unfortunately, bibliographic analysis reveals the relative scarceness of research about sampling methods and qualitative or quantitative characteristics of these fish communities. This is quite surprising considering the importance of the ditchwed of this kind of environment outlined by several authors. In the Netherlands, BELTMANN (1984) assessed that there is a total of 400 000 km of ditches. In France, the littoral dyked marshes of the Atlantic coast couid comprise 20 000 km of ditches and about 24 000 ha of open water. The present work provides for the first data on the fish community of Bourgneuf marsh.The northern part of the marsh of Bourgneuf, 2 700 ha provided whith f reshwater, contains nearly every kind of landscapes found throughout the whole Breton-Vendéen marsh. The pattern of the ditch network strongly changes from a zone to another (fig.1) : presence of former salt pans in the western part, regular geometric shapes in the recently created polders next to the River Falleron, irregular ditchweb pattern in the eastern part. The average density of the ditch network is 91 m of ditches per ha, totalizing 234 km in the study area. The total surface of open water, composed of ditches and basins (former salt pans), covers 411 ha (over 15 % of the study site). Diversity of ditch types occurs at fine scales (<1 000 m2), they vary according to their widths (0,3 to 7 m), depths (average, 42 cm; SD, 20,4), thickness of silt layer (average, 43 cm; SD, 42) and their hydrophyte vegetation cover (average, ... |
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