SILVERING OF FEMALE EELS (ANGUILLA ANGUILLA) IN TWO SUB-POPULATIONS OF THE RHÔNE DELTA.
The eel population of the Camargue lagoon system can be divided into two subunits living in two distinct biotopes (freshwater and brackish water) and characterised by different population structures and especially growth patterns. The sub-population living in the Fumemorte canal (average salinity: 0...
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ftdoajarticles:oai:doaj.org/article:f6d4f54e00f341668ba503b385488a03 2023-05-15T13:27:29+02:00 SILVERING OF FEMALE EELS (ANGUILLA ANGUILLA) IN TWO SUB-POPULATIONS OF THE RHÔNE DELTA. ACOU A. LEFEBVRE F. CONTOURNET P. POIZAT G. PANFILI J. CRIVELLI A. J. 2003-07-01T00:00:00Z https://doi.org/10.1051/kmae:2003036 https://doaj.org/article/f6d4f54e00f341668ba503b385488a03 EN eng EDP Sciences http://dx.doi.org/10.1051/kmae:2003036 https://doaj.org/toc/1961-9502 1961-9502 doi:10.1051/kmae:2003036 https://doaj.org/article/f6d4f54e00f341668ba503b385488a03 Knowledge and Management of Aquatic Ecosystems, Vol 0, Iss 368, Pp 55-68 (2003) European eel Anguilla anguilla silvering ocular index gonadosomatic index growth pattern age at metamorphosis freshwater brackish water Aquaculture. Fisheries. Angling SH1-691 article 2003 ftdoajarticles https://doi.org/10.1051/kmae:2003036 2022-12-31T10:21:22Z The eel population of the Camargue lagoon system can be divided into two subunits living in two distinct biotopes (freshwater and brackish water) and characterised by different population structures and especially growth patterns. The sub-population living in the Fumemorte canal (average salinity: 0.9 g/l) is a freshwater population type (81.6% females, maximum ages observed = 9 - 11 years, slow growth (annual gain 46 mm)) whereas that of the Vaccarès lagoon (average salinity: 9.7 g/l over the same period) is typical of a lagoon (45.6% females, maximum ages 5 – 6 years, fast growth (annual gain 90 mm)). In each sub-population, Gonadosomatic Index (GSI) and OI (Ocular Index) were measured on female eels over a sampling period that started in January 1997 and ended in December 2000. In both types of habitat, and in agreement with previous studies, we observed a threshold value of GSI ≥ 1.4 % characterising the silver stage (MARCHELIDON et al., 1999). The increase in eye area was a progressive phenomenon, initiated in the yellow stage and was significantly correlated (p < 0.001) with the GSI. As with the GSI, OI increased in silver eels, the threshold value of ≥ 8.0 discriminating silver eels. We will show that silvering follows different patterns between the two habitats. Age at metamorphosis in female eels take place very early in the Vaccarès lagoon (83.3% of females metamorphose between 4 and 5 years) compared to those in the Fumemorte drainage canal (94% of females metamorphose between 7 and 9 years). We suggest that the growth potential provided by Vaccarès lagoon accounts for this difference in age at metamorphosis. Although, such a turnover cannot explain alone the different proportions of female silver eels observed in the Fumemorte drainage canal (23%) and Vaccarès lagoon (2.4%). Influence of population’s parameters like sex-ratio, population structure and abundance on silvering process, is discussed. Article in Journal/Newspaper Anguilla anguilla Directory of Open Access Journals: DOAJ Articles |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
European eel Anguilla anguilla silvering ocular index gonadosomatic index growth pattern age at metamorphosis freshwater brackish water Aquaculture. Fisheries. Angling SH1-691 |
spellingShingle |
European eel Anguilla anguilla silvering ocular index gonadosomatic index growth pattern age at metamorphosis freshwater brackish water Aquaculture. Fisheries. Angling SH1-691 ACOU A. LEFEBVRE F. CONTOURNET P. POIZAT G. PANFILI J. CRIVELLI A. J. SILVERING OF FEMALE EELS (ANGUILLA ANGUILLA) IN TWO SUB-POPULATIONS OF THE RHÔNE DELTA. |
topic_facet |
European eel Anguilla anguilla silvering ocular index gonadosomatic index growth pattern age at metamorphosis freshwater brackish water Aquaculture. Fisheries. Angling SH1-691 |
description |
The eel population of the Camargue lagoon system can be divided into two subunits living in two distinct biotopes (freshwater and brackish water) and characterised by different population structures and especially growth patterns. The sub-population living in the Fumemorte canal (average salinity: 0.9 g/l) is a freshwater population type (81.6% females, maximum ages observed = 9 - 11 years, slow growth (annual gain 46 mm)) whereas that of the Vaccarès lagoon (average salinity: 9.7 g/l over the same period) is typical of a lagoon (45.6% females, maximum ages 5 – 6 years, fast growth (annual gain 90 mm)). In each sub-population, Gonadosomatic Index (GSI) and OI (Ocular Index) were measured on female eels over a sampling period that started in January 1997 and ended in December 2000. In both types of habitat, and in agreement with previous studies, we observed a threshold value of GSI ≥ 1.4 % characterising the silver stage (MARCHELIDON et al., 1999). The increase in eye area was a progressive phenomenon, initiated in the yellow stage and was significantly correlated (p < 0.001) with the GSI. As with the GSI, OI increased in silver eels, the threshold value of ≥ 8.0 discriminating silver eels. We will show that silvering follows different patterns between the two habitats. Age at metamorphosis in female eels take place very early in the Vaccarès lagoon (83.3% of females metamorphose between 4 and 5 years) compared to those in the Fumemorte drainage canal (94% of females metamorphose between 7 and 9 years). We suggest that the growth potential provided by Vaccarès lagoon accounts for this difference in age at metamorphosis. Although, such a turnover cannot explain alone the different proportions of female silver eels observed in the Fumemorte drainage canal (23%) and Vaccarès lagoon (2.4%). Influence of population’s parameters like sex-ratio, population structure and abundance on silvering process, is discussed. |
format |
Article in Journal/Newspaper |
author |
ACOU A. LEFEBVRE F. CONTOURNET P. POIZAT G. PANFILI J. CRIVELLI A. J. |
author_facet |
ACOU A. LEFEBVRE F. CONTOURNET P. POIZAT G. PANFILI J. CRIVELLI A. J. |
author_sort |
ACOU A. |
title |
SILVERING OF FEMALE EELS (ANGUILLA ANGUILLA) IN TWO SUB-POPULATIONS OF THE RHÔNE DELTA. |
title_short |
SILVERING OF FEMALE EELS (ANGUILLA ANGUILLA) IN TWO SUB-POPULATIONS OF THE RHÔNE DELTA. |
title_full |
SILVERING OF FEMALE EELS (ANGUILLA ANGUILLA) IN TWO SUB-POPULATIONS OF THE RHÔNE DELTA. |
title_fullStr |
SILVERING OF FEMALE EELS (ANGUILLA ANGUILLA) IN TWO SUB-POPULATIONS OF THE RHÔNE DELTA. |
title_full_unstemmed |
SILVERING OF FEMALE EELS (ANGUILLA ANGUILLA) IN TWO SUB-POPULATIONS OF THE RHÔNE DELTA. |
title_sort |
silvering of female eels (anguilla anguilla) in two sub-populations of the rhône delta. |
publisher |
EDP Sciences |
publishDate |
2003 |
url |
https://doi.org/10.1051/kmae:2003036 https://doaj.org/article/f6d4f54e00f341668ba503b385488a03 |
genre |
Anguilla anguilla |
genre_facet |
Anguilla anguilla |
op_source |
Knowledge and Management of Aquatic Ecosystems, Vol 0, Iss 368, Pp 55-68 (2003) |
op_relation |
http://dx.doi.org/10.1051/kmae:2003036 https://doaj.org/toc/1961-9502 1961-9502 doi:10.1051/kmae:2003036 https://doaj.org/article/f6d4f54e00f341668ba503b385488a03 |
op_doi |
https://doi.org/10.1051/kmae:2003036 |
_version_ |
1766398726978404352 |