Cedric Briand

• PhD
• pôle milieu naturel et bassin versant at EPTB Vilaine

Stocks of European eel ( Anguilla anguilla ) have declined continuously and steadily, since 1980. A model, GEMAC, namely Glass Eel Model to Assess Compliance, has been developed with the objective of assessing anthropogenic impacts on glass eels in estuaries and evaluating the effects of management measures, to support initiatives aimed at helping...

The SUDOANG project aims at providing common tools to managers to support eel conservation in the SUDOE area (Spain, France and Portugal). VISUANG is the SUDOANG Interactive Web Application that will host all these tools. The application consists of an eel distribution atlas (GT1), assessments of mortalities caused by turbines and an atlas showing...

This report presents the calibration of the EDA model in France, Spain and Portugal during the SUDOANG project. The objective was to predict escapement of silver eel. https://sudoang.eu/en/task-groups/. Some of the outputs are detailed in the Atlas. https://www.researchgate.net/publication/357909065_Atlas_of_European_eel_distribution_Anguilla_angui...

In fisheries management, accurate stock assessment is pivotal to determine sustainable harvest levels or the scope of conservation measures. When assessment is decentralized and methods differ regionally, adopted approaches must be subjected to rigorous quality-checking, as biased assessments may mislead management decisions. To enable recovery of...

WKSMEEL is part of the roadmap defined by the WKFEA (Workshop on the future of eel advice). Experts from Japan, USA, Canada and Europe met to discuss modelling methods and the data necessary to support the development of a spatial assessment of the stock of European eel (Anguilla anguilla). Modelling of the European eel stock is envisioned as a two...

The Joint EIFAAC/ICES/GFCM Working group on eels (WGEEL) met by correspondence and video conference from September 7 – 10 September and 27 September – 4 October in 2021 to assess the state of the European eel and its fisheries, investigate the effects of contaminants on the reproductive capacity of the eel stock, discuss the findings of WKFEA, furt...

This study quantifies the processes involved in regulating the European eel population of Lough Neagh, a lake in Northern Ireland. The relationship between glass eel input and silver eel output for the 1923–1997 cohorts was best described by a Beverton–Holt stock recruitment model. Glass eel input time series was not complete and was thus derived f...

Mistrust between scientists and non-scientist stakeholders is a key challenge in fishery management. This problem is exacerbated with the use of complex models to support management: these models suffer from difficulties in communicating their results and a lack of confidence from end users. The European eel is an illustrative example; its complex...

1. Numerous studies have documented a change in the phenology of migration of diadromous fish in response to climate change. Only few studies have, however, been conducted simultaneously for multiple species and at a large spatial scale. 2. We investigated the change in the timing of upstream migration of diadromous fish species in France. We used...

The Joint EIFAAC/ICES/GFCM Working group on eels (WGEEL) met by correspondence and video conference from September 21–28 in 2020 to assess the state of the European eel, investigate the effects of habitat loss on the eel stock and its management, review and update the Stock Annex, prepare the 2021 Data Call and report on any updates to the scientif...

The decline and collapse of populations have been reported for a large range of taxa. Diadromous fishes migrate between fresh water and the sea and encounter many anthropogenic pressures during their complex life cycle. In spite of being of ecological, cultural and economic interest, diadromous fishes have been in decline for decades in many parts...

The diversity of detrimental factors impacting the European eel and the number of involved stakeholders pose a challenge for an effective stock management. Knowledge on the economic consequences of single management measures is required to better assess their implications for the involved sectors. This study summarizes the current knowledge on thre...

EDA (Eel Density Analysis) is a modelling tool which allows the prediction of yellow eel densities and silver eel escapement from electrofishing survey networks. The 2018 version of EDA (2.2.1) is based on a dataset of 29183 electrofishing operations compared to 24 541 for 2015 (version 2.2.0) and only 9 556 in the 2012 version (2.1). The larger da...

European eels (Anguilla anguilla) migrate between the southwestern Sargasso Sea and the European and Mediterranean coasts. In a recent paper in Current Biology, Naisbett-Jones et al. [1] claim to “provide the first evidence that they [eels] derive positional information from the Earth's magnetic field” and that this information guides their migrati...

The status of European eel is critical; the annual recruitment of glass eel to European waters in 2015 was 8.4% of the 1960–1979 level in the central southern European estuaries (ICES 2015). The causes of the decline are unclear, it has been hypnotized that it is linked to a strong reduction in the spawning stock due to overfishing, habitat destruc...

Given the importance of reliable recruitment estimates when assessing temperate eel stocks and enforcing appropriate management measures, surprisingly few analytical tools have been developed to estimate yearly glass eel recruitment. Of the models that do exist, large-scale models generally rely on strong assumptions relating to fishing activity, w...

The size of the European eel population is below safe biological limits. To assess the status of the stock properly, it is necessary to increase the number of recruitment series based on scientific monitoring. In this study, the spatio-temporal variation in glass eel density in a South European Atlantic estuary, the Oria, has been examined using ex...

EDA (Eel Density Analysis) is a modelling tool which allows the prediction of yel- low eel densities and silver eel escapement from electrofishing survey networks. The 2015 version of EDA (2.2) is based on a dataset of 24 541 electrofishing operations which is higher than the 9 556 operations used in the 2012 version. The larger dataset is explained...

Assessing the yellow eel stock in a river catchment is required to quantify the impact of anthropogenic pressures and to prioritize management actions. EDA model (Eel Density Analysis), coupling a GIS approach and a statistical eel distribution model, was used as the standard tool during for French national Eel Management Plan implementation. We pr...

The spatio-temporal migration patterns of European glass eel were studied in a long-standing tradition glass eel fishery estuary, the Oria. Catch logbooks were collected during nine fishing seasons (2003-2012) and fishery-independent experimental surveys were carried out at two sampling points during the fishing season from 2005 to 2012. Environmen...

Despite the importance of reliable recruitment estimates to assess eel stocks and enforce appropriate management measures, few analytical tools have been developed to estimate yearly glass-eel recruitments. Among existing models, large-scale models generally rely on strong assumptions regarding fishing activity while other models generally estimate...

Recruitment of the three northern hemisphere eel species (European eel Anguilla anguilla, American eel Anguilla rostrata and Japanese eel Anguilla japonica) has reduced significantly over the past thirty-five years. The stock of the European eel is described as being outside safe biological limits, with urgent action required by European Union Memb...

de la capture de civelles dans l'estuaire de la Seudre par l'utilisation du modèle GEMAC Traitement des données des saisons 2008-2009 et 2009-2010 Résumé : La pêcherie du système Seudre – Charente – Pertuis Charentais a fait l'objet d'une analyse sur les années 2006-2010, et les données de captures et d'effort ont été décrites séparément pour les n...

The objective of the European Commission Eel Recovery Plan (CR No 1100/2007) to protect and restore the European eel stock is to allow the escapement to the sea of at least 40% of the silver eel biomass relative to the pristine biomass. The Member states must submit a management plan progress report to the Commission every three years starting in 2...

Post fishing mortality of the glass eel was monitored in 2007 in the Vilaine estuary. The mortality of the glass eels varied from 2 to 82% (mean 42%) in the two days following the fishing. The mortality of samples collected by hand nets or from the trapping ladder was null. Alterations of the skin mucus were analyzed by the use of Indigo carmine. T...

Using commercial and fishery data, we recount the main features and key points of the historical trade of the European eel. Glass eel fisheries have been active since the end of the 19th century with landings estimated around 200 t. Fisheries and trade developed mainly in the south of France and markets expanded progressively along the Atlantic coa...

Using commercial and fishery data, we recount the main features and key points of the historical trade of the European eel. Glass eel fisheries have been active since the end of the 19 th century with landings estimated around 200 t. Fisheries and trade developed mainly in the south of France and markets expanded progressively along the Atlantic co...

This paper reports a study on the progeny sex-ratio distribution in the Florida red tilapia. This hybrid originated as a cross between O. mossambicus male and O. urolepis hornorum female, which was then crossed with O. niloticus and O. aureus in order to improve its growth rate and its resistance to low temperature. We have studied the sex-ratio of...

The pigmentation development process of glass eels Anguilla anguilla from stage VB to VIA3 was modelled by gamma cumulative functions. These functions varied with respect to the factors temperature and salinity whose effects were adjusted by beta functions. Temperature was shown to accelerate pigmentation, while salinity acted as a secondary factor...

The construction of the Arzal dam eel ladder in 1996 allowed enhancing fluvial recruitment from a negligible level, limited to yellow eels crossing sluice and dam overflow, to a level ranging from 0.2 to 2.4 million glass eels per year. The effect of such recruitment on the eel population (Anguilla anguilla) of the Vilaine watershed was analysed at...

Glass eels (Anguilla anguilla) arriving after the fishing season in the Vilaine estuary (France) were caught by boat and at a trapping ladder located at a blocking dam upstream in the estuary. They were marked with Bismarck brown, rhodamine B or neutral red, and released into the estuary. The effect of marking on behaviour, mortality and recapture...

The European eel population is in decline. Urgent management actions are required. To monitor their effect, we developed a fast sampling method, applicable in shallow rivers and tributaries. We compared the Carle & Strub estimator from 35 double pass electric fishing samples with Point Abundance Sampling by Electrofishing or PASE (24 point samples...

To determine whether thyroidal status is related to migratory and settling behaviour in Anguilla anguilla glass eels, we sampled glass eels showing different migratory behaviours in the Arzal dam, which constitutes the tidal limit of the Vilaine River (France). We collected 4 groups of glass eels: flood and ebb tide glass eels were netted in the es...

The evolution of pigment stages was monitored on six glass eel samples collected in the Vilaine estuary, and kept in cages in freshwater, and in the estuary. In each location, one sample was kept for reference to assess the effect of handling procedure on pigment development. It was pulled out the water only to monitor and retrieve mortality. The o...

A glass eel fishery exists downstream of the Arzal estuarine dam in the Vilaine (Brittany, France). Catch statistics were collected between 1996 and 2000, and processed using a subsampling technique which allowed data from a reliable subsample to be extrapolated to the whole fishery. During the same period, glass eel migration into fresh water was...

Les anguilles prélevées dans cinq zones de salinité variable du littoral de Bretagne sud, ont été examinées pour leur infestation présente et passée par le parasite Anguillicola crassus (Nematoda, dracunculoidea). Les anguilles vivant dans des milieux peu salés au contact de la zone dulçaquicole sont très contaminées avec des prévalences supérieure...

A double mark, called a transition ring, or elver mark, was identifiable in light microscopy on otoliths of young yellow eels. In the Vilaine watershed, the radius of this mark decreased from 178 mum in yellow eels corresponding to glass eels arriving in autumn 1997 to 163 mum in yellow eels arriving in spring 1998. The mean transition ring radius...

Eels were sampled in five areas of variable salinity from the coast of south Brittany and examined for their past and present infection by the parasite Anguillicola crassus (Nematoda, dracunculoidea). Eels living in low salinity areas, in contact to the freshwater area, were highly contaminated with prevalence larger than 90 %, with 61% concerning...

Anguillid eels are well known as catadromous highly migratory species, with marine spawning grounds well separated from inshore and inland growth areas. However, invasion mechanisms of river systems are poorly documented. This theory is based upon the identification of four distinct movement behaviors: „founders“ that colonize rivers until they set...

The influence of eel odour on the efficiency of a freshwater eel ladder and trap was assessed during two glass eel and yellow eel springtime upstream migration seasons in the Vilaine estuary, France. This test consisted of alternatively directing the outflow from the trap holding bin, away from, or onto the trap access ladder and comparing catches....

Post fishing mortalities of glass eels have been monitored in 2007 in the Vilaine estuary. The mortality of glass eel varied from 2 to 82% (mean 42%) in the two days following the fishery. The mortality of samples collected by hand nets or from the trapping ladder was null. Alterations of the skin mucus were analyzed by the used of indigo carmin. T...

La construction de la passé à anguille d’Arzal en 1996 a permis d’augmenter les passages de la passe d’Arzal, d’un niveau quasi nul, limité aux anguilles passant au travers de l’écluse et des surverses du barrage, à un niveau variant entre 0,2 et 2,4 millions de civelles par an. L’effet d’un tel recrutement sur la population d’anguilles (Anguilla a...