The silvering process of <i>Anguilla anguilla</i>: a new classification from the yellow resident to the silver migrating stage

Durif, Caroline; Dufour, Sylvie; Élie, Pierre

doi:10.1111/j.0022-1112.2005.00662.x

Cited by 324 publications

(415 citation statements)

References 56 publications

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“…However, the average length or weight of tagged eels did not differ significantly between the capture sites within each year (2-way ANOVA, year × site interaction, F 1, 95 = 3.7 for length and F 1, 95 = 1.01 for weight, p > 0.05 in both cases, Table S1 in the Supplement). The maturity of each eel was judged by 2 indices, the ratio between eye area and body length (BL) (Pankhurst 1982) and the ratio between the length of the pectoral fin and BL (Durif et al 2005). According to those indices, all eels were in the silver eel stage.…”

Section: Eel Tagging and Releasementioning

confidence: 99%

Behaviour of stocked and naturally recruited European eels during migration

Westerberg

Sjöberg²,

Lagenfelt³

et al. 2014

Mar. Ecol. Prog. Ser.

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One objection to the stocking of translocated eels as a management measure for the European eel Anguilla anguilla L. is that these eels may lack the ability to find their way back to the spawning area in the Sargasso Sea because the translocation will confuse their imprinted navigation. We undertook a series of tagging experiments using satellite tags, data storage tags and acoustic tags to test the hypothesis that eels translocated 1200 km from the UK to Sweden differed in their ability to migrate compared to naturally recruited eels. Eels to be tagged were caught in 2 locations, one with a record of eel stocking for more than 20 yr and with a series of barriers to upstream migration and another in a river with only natural immigration and without barriers to upstream migration. In the first year, the naturally recruited and stocked eels were released in a fjord where the initial escapement behaviour could be monitored by acoustic tagging in addition to using archival tags to track the subsequent marine migration. In the second year, eels were tagged with archival or satellite tags and released on the open coast, and only their marine migration was investigated. Eels were tracked more than 2000 km along a route that, after leaving the Skagerrak, followed the Norwegian Trench to the Norwegian Sea, turned south and west along the Faroe-Shetland channel before emerging into the Atlantic Ocean, and then continued west. There were no statistically significant differences in estuarine or oceanic behaviour regarding route, swimming speed and preferred swimming depth between stocked and naturally recruited eels. These results provide the first empirical evidence of a Nordic migration route and do not support the hypothesis that a sequential imprinting of the route during immigration is necessary for adequate orientation or behaviour during the adult spawning migration.

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Section: Eel Tagging and Releasementioning

confidence: 99%

Behaviour of stocked and naturally recruited European eels during migration

Westerberg

Sjöberg²,

Lagenfelt³

et al. 2014

Mar. Ecol. Prog. Ser.

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“…Although the ocular hypertrophy values (OI > 6.5) should be considered as a criterion for silver eel determination (Acou et al, 2005) it was not calculated in the field for logistic reasons. However, Durif et al (2005) showed that the increase in the ocular diameter appears before the pigmentation change, therefore we considered it valid to use only the two criteria. Silver eels were marked with acrylic paint ("Van Gogh" permanent green light 618) and ink ("Magic Color" process magenta MC 620).…”

Section: > Colour-marking Experimentsmentioning

confidence: 99%

Silver eel population size and escapement in a Mediterranean lagoon: Bages-Sigean, France

Amilhat

Farrugio

Lecomte-Finiger

et al. 2008

Knowl. Managt. Aquatic Ecosyst.

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Much concern has been raised about the decline in the European eel (Anguilla anguilla) population. European management plans for the recovery of the stock are now in preparation, the main objective being to increase the escapement of the potential spawners (silver eels) in each basin to allow 40% of the pristine biomass to escape. However, there are relatively few studies on silver eel escapement and production, and no recent measurement of escapement in lagoons, habitats which support large silver eel sub-populations in the Mediterranean region. A markrecapture study was carried out in autumn 2007 in order to estimate the number of silver eels migrating from the Bages-Sigean lagoon in the SouthWest of France. The migrating population, mostly males between 36 and 42 cm, was estimated to be around 1 120 000 eels (30 kg·ha -1 ). The exploitation rate by professional fishermen was around 20% (6 kg·ha -1 ), leading to an escapement level of 80% (24 kg·ha -1 ). The results are discussed regarding the available data in the literature on silver eel escapement. RÉSUMÉTaille et échappement de la population d'anguilles argentées d'une lagune méditerranéenne : Bages-Sigean, FranceLe déclin de l'anguille européenne Anguilla anguilla est très préoccupant et chaque pays européen a maintenant le devoir de préparer un plan de gestion pour la reconstitution du stock. Le principal objectif est d'assurer un taux d'échappement d'au moins 40 % de la biomasse pristine des anguilles argentées (futurs géniteurs) vers leur lieu de reproduction. Cependant, très peu de recherches ont été menées sur l'estimation du stock et du taux d'échappement des anguilles argentées et aucune estimation récente du taux d'échappement n'avait encore été réalisée en Méditerranée. Cette étude de marquage-recapture a été réalisée en automne 2007 dans le but d'estimer la quantité d'anguilles argentées migrantes de la lagune de Bages-Sigean. La population migrante, principalement des mâles entre 36 et 42 cm, a été estimée à 1 120 000 anguilles (30 kg·ha -1 ). Le taux d'exploitation par les pêcheurs professionnels évalué à 20 % (6 kg·ha -1 ) laisse suggérer un taux d'échappement de 80 % (24 kg·ha -1 ). Les résultats sont discutés au regard de la littérature disponible sur l'échappement des anguilles argentées.

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“…Later in the season, some eels build up higher lipid contents and start to migrate to sea to begin their journey to the Sargasso Sea [11]. Although those 'silver eels' can be distinguished by their grey colour, in contrast with the regular 'yellow eel', mistakes in this identification can be made [12]. Farmed eel were purchased from 11 Dutch eel farmers.…”

Section: Eel Studymentioning

confidence: 99%

Polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls in fish from the Netherlands: concentrations, profiles and comparison with DR CALUX® bioassay results

Leeuwen

Leonards

Traag³

et al. 2007

Anal Bioanal Chem

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Fish from Dutch markets were analysed for concentrations of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DLPCBs) and compared with the new European maximum residue levels (MRLs), set in 2006. In a first study on 11 different fish and shellfish from various locations, concentrations of PCDD/Fs were nearly all below the MRL for PCDD/Fs [4 pg toxic equivalents (TEQ) per gram wet weight (ww)] and nearly all below 8 pg total TEQ/g ww, the new MRL for the sum of PCDD/Fs and DL-PCBs. Some samples exceeded the total TEQ MRL, such as anchovy, tuna and sea bass. Furthermore, 20 (out of 39) wild eel samples exceeded the specific MRL for eel (12 pg total TEQ/g ww), as the study revealed PCDD/F TEQ levels of 0.2-7.9 pg TEQ/g ww and total TEQ values of 0.9 to 52 pg/g ww. TEQ levels in farmed and imported eel were lower and complied with the MRLs. Smoking eel, a popular tradition in the Netherlands, only had marginal effects on PCDD/F and DL-PCB concentrations. Owing to volatilization, concentrations of lowerchlorinated PCBs were reduced to below the limit of quantification after smoking. DL-PCBs contributed 61-97% to the total TEQ in all eel samples. This also holds for other fish and shellfish (except shrimps): DL-PCB contributed (on average) from 53 (herring) to 83% (tuna) to the total TEQ. Principal-component analysis revealed distinctive congener profiles for PCDD/Fs and non-ortho PCBs for mussels, pikeperch, herring and various Mediterranean fish. The application of new TCDD toxic equivalency factors (TEFs) set by the World Health Organization in 2006 (to replace the 1997 TEFs) resulted in lower TEQ values, mainly owing to a decreased mono-ortho PCB contribution. This decrease is most pronounced for eel, owing to the relative high monoortho PCB concentrations in eel. Consequently, a larger number of samples would comply with the MRLs when the new TEFs are applied. The DR CALUX® assay may be used for screening total TEQ levels in eel, in combination with gas chromatography-high resolution mass spectrometry confirmation of suspected samples. An almost 1:1 correlation was found when the 1997 TEFs were applied, but, surprisingly, a 1.4-fold overestimation occurred with application of the 2006 TEFs.

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The silvering process of Anguilla anguilla: a new classification from the yellow resident to the silver migrating stage

Cited by 324 publications

References 56 publications

Behaviour of stocked and naturally recruited European eels during migration

Behaviour of stocked and naturally recruited European eels during migration

Silver eel population size and escapement in a Mediterranean lagoon: Bages-Sigean, France

Polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls in fish from the Netherlands: concentrations, profiles and comparison with DR CALUX® bioassay results

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