État des communautés benthiques sous les cages d’élevage de salmonidés (Rade de Cherbourg). Projet SALMOCOT III
Dauvin, J.C.; Baux, N.; Mear, Y. (2024). État des communautés benthiques sous les cages d’élevage de salmonidés (Rade de Cherbourg). Projet SALMOCOT III. Cnam-Intechmer/LUSAC: Cherbourg-en-Cotentin. 34 pp.
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| Keywords |
Aquaculture
Benthic communities
Human impact
Marine/Coastal |
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| Authors | | Top |
- Dauvin, J.C., more
- Baux, N.
- Mear, Y.
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| Abstract |
Since 1985, the Cherbourg roadstead has been the subject of environmental monitoring, covering the water mass as well as the biota and marine sediments. This monitoring is part of the CHERAD program, which monitors the bay. The close collaboration between the CNAM-Intechmer research team and the managers of a salmonid farm in the bay has led to the implementation of a series of more specific actions gathered in the SALMOCOT project. SALMOCOT III was implemented in 2023, when the salmon farm (Salmo salar) was restructured. In this report, an analysis of the benthic communities (benthic macrofauna and analysis of the nature of the sediments), under the cages located in the large roadstead, was carried out, in order to assess the state of the communities following the cessation of rearing for two years and before the return to water of a new population of fish. On February 2, 2024, at the salmon cage site, four stations in the Grande Rade were surveyed. The year 2024 was characterized by average taxonomic richness, very low abundances and biomasses, and a very good to average ecological diagnosis, depending on the station. Sediment differences were also observed. For 2024, the various analyses show specific faunal compositions and abundances for each station sampled. The 2014-2024 comparisons (cages in operation in 2014) show two very clear-cut situations between 2014, with a rich fauna characteristic of a zone enriched in organic matter, and 2024, where an impoverished fauna with no indication of species indicative of organic matter enrichment is observed. This may be linked to the cessation of fish farming over the past 2 years (empty cages), which contributed directly to the local supply of organic matter via food scraps and fish faeces. With the temporary cessation of fish farming, organic matter is no longer present, and a fauna composed of species that are not indicative of organic matter enrichment has settled in. This fauna is not very abundant and diversified, probably due to the presence of a substrate composed of a large quantity of shell debris and whole oyster and scallop shells, making it difficult for endofauna to establish themselves. |
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