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Une méthode de détermination externe du sexe basée sur le dimorphisme sexuel de la longueur relative de la mâchoire supérieure est appliquée chez le Saumon Atlantique (Salmo salar L.). 78 adultes capturés en juin et juillet 1990 dans trois rivières des Asturies (Nord de l'Espagne) sont étudiés. L'Analyse Linéaire Discriminante sur un échantillon de 63 poissons donne un pourcentage d'erreurs de moins de 10 %. Les résultats sont comparés à ceux obtenus sur d'autres cours d'eaux d e l'aire de répartition du Saumon atlantique et sont discutés en fonction de la composition de l'échantillon.

Deux méthodes d'estimation de la production en smolts de saumon atlantique (Salmo salar L.) sont comparées sur la rivière Oir, affluent de la Sélune (Basse-Normandie). La première estime le nombre de smolts par l'analyse des caractéristiques de l'habitat et du phénomène de bimodalité de taille observée dans la population 0 + en automne. La seconde méthode évalue la production en smolts à partir des captures par piégeage. L'étude montre que les estimations réalisées par les deux méthodes sont proches avec cependant des différences plus ou moins importantes selon l'année et la classe d'âge. Elle montre également que les smolts proviennent essentiellement de la population automnale de 0 + à forte croissance. Enfin, les valeurs de taux de survie hivernale utilisées dans la première méthode permettent d'obtenir des estimations du nombre de smolts 1 + proches de celles faites par piégeage, les résultats sont moins fiables pour les smolts 2+. Les résultats sont discutés et différents aspects sont analysés en vue d'améliorer la concordance entre les deux méthodes.

This study provides new data on Atlantic salmon Salmo salar life-history traits across France. Using a long-term recreational angling database (1987-2013) covering 34 rivers in three regions (genetic units), a decline in individual length, mass and a delayed adult return to French rivers was reported. Temporal similarities in trait variations between regions may be attributed to common change in environmental conditions at sea. The relative rate of change in phenotypic traits was more pronounced in early maturing fish [1 sea-winter ( 1SW) fish] than in late maturing fish ( 2SW fish). Such contrasted response within populations highlights the need to account for the diversity in life histories when exploring mechanisms of phenotypic change in S. salar. Such detailed life-history data on returning S. salar have not previously been reported from France. This study on French populations also contributes to reducing the gap in knowledge by providing further empirical evidence of a global pattern in S. salar across its distribution range. Results are consistent with the hypothesis that the observed changes in life-history traits are primarily associated with environmental changes in the North Atlantic Ocean. They also emphasize the presence of less important, but still significant contrasts between region and life history. [ABSTRACT FROM AUTHOR]

A von Bertalanffy growth model for young-of the-year Atlantic salmon Salmo salar in a small French coastal stream was fitted using water temperatures and densities of juvenile salmonids ( S. salar and brown trout Salmo trutta) as covariates influencing daily growth rate. The Bayesian framework was used as a template to integrate prior information from external data sets. The relative influence of the covariates on parr growth was quantified and results showed that growth of S. salar juveniles depended on both water temperatures and densities, but that most of the spatiotemporal variability of growth resulted from local spatiotemporal variations of 0+ age salmonid ( S. salar and S. trutta) densities. Further analysis revealed that the fluctuations in young-of-the-year salmonid densities are likely to dominate the effects of potential future warming of water temperature due to climate change. It is concluded that factors that could affect salmonid densities might well have a greater effect on S. salar population dynamics than factors influencing water temperatures. [ABSTRACT FROM AUTHOR]

A large salmonid was caught in the commercial fisheries in the River Rhoˆne (Mediterranean basin, France). Using morphological criteria and DNA analysis, the fish has been identified as an adult Atlantic salmon Salmo salar. [Copyright &y& Elsevier]

This paper presents some characteristics (length, weight and age) of adult Atlantic salmon in rivers of Brittany. The data were derived from 1,578 fish caught mainly by rod and line; the remainder being from net catches in estuaries and small samples taken outside the fishing season. The bulk of the fish spent 1 or 2 years in freshwater before smoltifying. Those fish becoming smolts at the end of 1 year were the most numerous (54%). The majority of the fish sampled were spring fish (82.4%). Very few summer fish were identified and those found were mainly grilse. The high proportion of spring fish in the sample is due to the high proportion of rod-caught fish. Probably a complete census over the year would show a larger proportion of grilse and summer fish as these are not subject to heavy rod-fishing the season being closed at the beginning of June. The relationship between sea age and river age and the influence of freshwater life upon the sea life were tested in four rivers. It seems probable that sea life depends chiefly on the river and the year of smoltification rather than on the freshwater stage. The biometric characteristics of Brittany salmon were compared with data from some foreign rivers. The angling exploitation of the spring Atlantic salmon in Brittany and the lack of data about summer migrations are discussed in regard to the future of this stock. [ABSTRACT FROM AUTHOR]