The European eel (Anguilla anguilla) is drastically declining in all its distribution area and listed in the red list of the IUCN (International Union for Conservation of Nature). A rebuilding plan was adopted at European level in 2007, Regulation R(CE) 100/2007, to restore eel abundance to the level observed during the seventies. Its implementation started on the 1st of January 2009. This species is heavily threatened by numerous activities including fishing, and its management can only be effective through a systemic approach minimizing the whole range of human-induced impacts on the resource and its habitat. In the framework of the European interregional programme INTERREG IIIB-Atlantic Area– the INDICANG project aimed at elaborating abundance indicators of the European eel in the central part of its distribution area (http://www.ifremer/fr/indicang/). A methodological guide was elaborated by this project to define the indicators needed for this resource assessment. In this framework, Ifremer (Institut Français pour l'Exploitation de la Mer) and the UPPA University (Université de Pau et des Pays de l'Adour) have developed a method to estimate the daily and seasonal biomass of glass eels with the view to evaluate the fishery's impact on the estuarine eel recruitment to the Adour catchment. The estimation method uses observations from nightly scientific surveys to estimate glass eels' densities in the water column during various flood tides characterized by different hydrodynamic conditions. Information on these conditions allows the estimation of the glass eels biomass migrating during the night. From these estimates and reported catches made by the fishery during the same night, the exploitation rate applied by the fishery on the flow of glass eels progressing upstream during night flood tides is estimated. The relationship between the exploitation rate, fishery catches and hydrodynamic conditions allowed the estimation of the exploitation rate and nocturnal biomass fluctuations during the fishing season, from November 1st to March 31st of the following year. Finally, from the chronological series of biomass migrating at night, the total biomass migrating every day and the total recruitment into the estuary, during the main glass eel migration period, are estimated. Estimations made between 1998 and 2005 indicate that the overall rate of exploitation of the marine and continental fisheries, on average, is of 15.7%, ranging between 8 and 25% according to fishing seasons.

Implementing the Ecosystem Approach to Fisheries is a demanding exercise even though a more or less sophisticated approach might be adopted depending on the fishery or problem concerned and on the capacity available to deal with it. In France, DEMOSTEM, a programme of Ifremer was established to try to practically apply the EAF principles across the high diversity of situations existing in the country. The article summarizes very briefly the lessons learned through this programme implementation and some of the key findings and outcomes. In conclusion, it offers some perspectives on the whole process.

The studies carried out on the Adour estuary on the migration of glass eels lead to the characterisation of their swimming behavior. Individuals migrate passively with the flood tide current behind the dynamic tide front, and their movements into the water column are linked to the surrounding luminosity and water turbidity. A numerical model was built from observations gathered on glass eel densities during scientific surveys. It uses the outputs of a hydrodynamic model accounting for the variations in the river flow and tide coefficient. It allows the simulation of the displacement of a particle in the longitudinal axis of the estuary. The variation of the vertical movements through the water column takes into account the cloud cover, the moon phases, the alternation of days and nights and the water turbidity. The results allow displaying the migration speed of groups of glass eels entering the Adour estuary. These simulations are validated by the comparison with in situ observations and the outputs of the behavioral model make possible, on the one hand, to simulate the migration speed of glass eels according to hydrological data and, on the other hand, to define the environmental conditions that stop or slow down their displacement into the estuary.

Les caractéristiques biologiques des civelles (Anguilla anguilla) ont été étudiées entre novembre et mars lors de deux campagnes d'échantillonnage successives (1996–1997 et 1997–1998) dans l'estuaire de l'Adour. Une diminution de la longueur (en moyenne de 73,5 à 67,4 mm) et du poids (en moyenne de 3,5 à 2,6 dg) des civelles durant la saison de migration est observée comme sur les autres estuaires. Différents groupes de civelles peuvent être identifiés au cours de chaque saison étudiée. Les variations du coefficient d'allométrie statique et de l'indice de similarité indiquent l'arrivée successive de différents flux dans le bas estuaire. Ces groupes sont bien différenciés lors de la première campagne alors qu'ils se chevauchent dans le temps lors de la seconde. La conjonction de forts débits fluviaux et de faibles coefficients de marée induit des conditions de migration défavorables pour les civelles qui pénètrent en estuaire. Après accumulation des bancs de civelles dans la partie basse de l'estuaire, quand les conditions hydrologiques redeviennent favorables, les bancs mélangés remontent vers l'amont par « vagues » successives, au rythme des marées.

Dans cet article, nous étudions les associations entre variables qualitatives. Nous présentons une approche basée sur l'utilisation du modèle loglinéaire. Appliqués aux associations entre captures par unité d'effort (cpue) d'aloses (Alosa alosa), coefficient de marée (cm) et débit fluvial (df), différents modèles mettent en évidence que les captures par unité d'effort augmentent proportionnellement à la valeur du coefficient de marée et qu'elles ont des évolutions conjointes moins structurées avec le débit fluvial.

L'étude des carnets de pêche des marins-pêcheurs et l'échantillonnage des captures ont permis de cerner les caractéristiques biologiques des populations de grandes aloses (Alosa alosa L.) prélevées sur l'Adour de 1988 à 1991 et d'étudier l'influence des conditions hydroclimatiques sur le niveau moyen des captures journalières par sortie. Les aloses sont principalement recrutées dans l'estuaire entre le début du mois d'avril et la fin du mois de mai: entre 78 et 89 % selon les années. Les mâles sont en moyenne plus jeunes et à âge égal plus petits et moins lourds que les femelles. Ces résultats confortent les connaissances obtenues sur les principaux stocks français qui remontent les systèmes fluviaux de la Loire et de la Gironde. Les analyses effectuées soit par l'Analyse Factorielle des Correspondances soit par l'utilisation du Modèle Linéaire Généralisé indiquent que les variations conjuguées du débit fluvial et du coefficient de marée ont une influence sur l'abondance des captures journalières exprimées en kg par sortie. Le travail réalisé à l'aide de ces deux méthodes complémentaires d'analyse permet à la fois de décrire et de quantifier les liens entre les captures par sortie (CPUE) et les facteurs hydroclimatiques. En effet, une augmentation de ces CPUE est constatée avec l'accroissement des coefficients de marée, le débit fluvial intervenant comme facteur de modulation secondaire.

Two techniques of stock discrimination both utilizing scales, i. e. termed as classical technique and shape analysis, are compared for discriminating between North American and European Atlantic salmon (Salmo salar L.) caught off West Greenland. Three scales from each of 60 salmon were analyzed: 30 from North American and 30 from European-origin salmon collected from home rivers in 1982. The best results indicated misclassification and error rates of 0% for shape analysis and 5.0% and ± 1.7%, respectively, for the classical technique. A nested ANOVA indicated that variation was greater between scales of salmon of North American and European origin than from several scales from the same salmon. It was concluded that shape analysis with computer-aided devices may be superior to the classical technique and it is recommended that it be examined for use at West Greenland.

The general characteristics of the main salmon (Salmo salar L.) stocks in the Massif armoricain (Brittany and Lower Normandy), in the Loire-Allier and in the Adour-Gaves-Nive have been summarized. Due to the poor quality of the previous fishing statistics, there is no clear picture of the historical evolution of the salmon stock. However, a dramatic decrease in the endemic range of Atlantic salmon in France can be shown since the mid-18th century and more particularly during the last 50 years. The lack of precise informations describing the size of the catches and the levels of exploitation at sea and in the estuaries make it impossible to estimate the impact that exploitation has led on the evolution of salmon stocks. The mean age of salmon in freshwater ranges from 1 to 1.5 years. The Loire-Allier basin is characterized by a relatively high proportion of large salmon (3 fish) in the rod catches. Fish native to Brittany and Lower-Normandy (Massif armoricain) have lover growth rates than those from the Loire-Allier and Adour-Gaves-Nice Basins. A greater proportion of the early grilse stocks (migration May-July) are males than compared with fish running later. The sex ratio of the multi-sea-winter salmon is biased towards females.

The use of an image analysis microsystem with a specially developed software enabled scale image processing, outline extraction and computation of features which are not available in the conventional approach of scale analysis. Those parameters (shape factors, moment invariants and elliptic Fourier coefficients) were introduced into a discriminant analysis process to test their usefulness in stock identification. The method was applied to European stocks originating from Norway (Etne river) and France (Elorn river). The low misclassification rate obtained indicates that this approach is particularly promising.