Predation on migrating eels (Anguilla anguilla L.) from the Western Mediterranean

Nineteen female silver European eels (Anguilla anguilla L.) were tagged with satellite tags and released in the Gulf of Lion in the Mediterranean during the migration seasons 2013 and 2015. Sixteen tags transmitted data: five in the Atlantic Ocean, and eleven in the Mediterranean. Of those, 50% of migrating eels were consumed by marine mammals in each year, all in the Mediterranean. The diving behaviour recorded by the tags after the eels were consumed indicated that the most likely predators were deep diving toothed whales. Measurements of the acoustic target strength of the tag showed a negligible effect on the detectability by whale biosonar. Overall, the observed predation rate was similar to that reported for eels escaping into the Atlantic. However, unlike eels in the Atlantic, which are most vulnerable to predators in the first week of escapement as they traverse the continental shelf and before they reach the refuge of the deep ocean, eels escaping from the Mediterranean were predated in deep water, months after release, likely as a consequence of their migration within a relatively narrow and deep corridor in the Alboran Sea. This emphasises the challenge of accounting for natural mortality in management plans for the long-term recovery of the European eel

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

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 mark-recapture study was carried out in autumn 2007 in order to estimate the number of silver eels migrating from the Bages-Sigean lagoon in the South-West 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.Le 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

Model prediction vs. reality--testing the predictions of a European eel (Anguilla anguilla) stock dynamics model against the in situ observation of silver eel escapement in compliance with the European eel regulation

A direct monitoring of European silver eel (Anguilla anguilla, L) escapement from rivers and estuaries has been proven to be challenging, and a Europe-wide documentation of escaping silver eel numbers therefore hardly seems realistic. To reinforce management decisions, policy-makers are thus widely reliant on the accuracy of escapement models. A 3-year programme of silver eel escapement monitoring was undertaken to compile model input data and revise an eel population model (German Eel Model II; GEM II) already used in the decision-making process of management authorities. By compiling necessary input data and analysing vital system-specific population characteristics, it was possible to compare the documented silver eel escapement with the modelled potential silver eel escapement. Resulting model predictions were close to actually monitored escapement numbers, which were distinctly lower than reference escapement values for the same freshwater system given in the implementation report of the German Eel Management Plans. Applying different commercial and recreational catch scenarios revealed the sensitivity of the model. The results show the potential of the GEM II and highlight the importance of high-quality input data to use model predictions as the basis for management measures

Knowledge and Management of Aquatic Ecosystems

ABSTRACT 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·h

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

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 mark-recapture study was carried out in autumn 2007 in order to estimate the number of silver eels migrating from the Bages-Sigean lagoon in the South-West 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

Culture et développement, la durabilité renouvelée par l'approche interculturelle ?

International audienc

Phthalate metabolites in the European eel (Anguilla anguilla) from Mediterranean coastal lagoons

International audienceThe levels and fate of phthalate metabolites have been poorly evaluated in fish, despite their potential ecotoxicological impacts. The present study aims to characterize the levels of phthalate metabolites in muscle tissue of yellow eels (Anguilla anguilla) from two coastal Mediterranean lagoons, during three sampling periods. Nine phthalate metabolites were detected in > 70% of the samples. Slightly higher levels of phthalate metabolites were detected in March and June compared to October, suggesting possible seasonal variations in environmental release and/or phthalate metabolization process by eels. The large sample size (N = 117) made it possible to explore correlations between phthalate metabolites' levels and individual parameters, such as body length, age, body condition and hepatic histo-pathologies. Body length and estimated age poorly correlated with phthalate metabolites, suggesting that eels did not accumulate phthalates during growth, contrary to persistent compounds. Eels presented different grades of hepatic fibrosis and lipidosis. A negative correlation was found between the severity of these pathologies in the liver and the sum of phthalate metabolites levels, supporting the hypothesis that eels with damaged liver are less able to metabolize xenobiotics

Complete genomic sequence and taxonomic position of Eel virus European X (EVEX), a rhabdovirus of European eel

Eel virus European X (EVEX) was first isolated from diseased European eel Anguilla anguilla in Japan at the end of seventies. The virus was tentatively classified into the Rhabdoviridae family on the basis of morphology and serological cross reactivity. This family of viruses is organized into six genera and currently comprises approximately 200 members, many of which are still unassigned because of the lack of molecular data. This work presents the morphological, biochemical and genetic characterizations of EVEX, and proposes a taxonomic classification for this virus. We provide its complete genome sequence, plus a comprehensive sequence comparison between isolates from different geographical origins. The genome encodes the five classical structural proteins plus an overlapping open reading frame in the phosphoprotein gene, coding for a putative C protein. Phylogenic relationship with other rhabdoviruses indicates that EVEX is most closely related to the Vesiculovirus genus and shares the highest identity with trout rhabdovirus 903/8