Temporal patterns in the upstream migration of European eels (Anguilla anguilla) at the Couesnon estuarine dam

The temporal migration patterns of European glass eel Anguilla anguilla at the Couesnon estuarine dam (Mont-Saint-Michel Bay, France)were examined in winter and spring 2004 and 2005. The dam which is located close to the river mouth constitutes a major obstacle for upstreammigrating glass eels. The migration was observed at different temporal scales, from within individual tides to complete tidal cycles between successive spring tides. The maximum number of glass eels arrived downstream of the dam at the beginning and in the middle of the flood tide. Glass eels migrated through the dam openings preferentially from the middle of the flood to the beginning of the ebb tide. Eel densities were highest during the second tide of each tide cycle that arrived at the estuarine dam and when the difference in water level between upstream and downstream of the dam was greatest, particularly at the end of the flood. Analysis of the influence of each environmental factor provided a good prediction of the glass eel recruitment peaks and, therefore, of the most favourable temporal windows for their migration. The water level and temperature were the most important environmental factors. These results provide the information needed for a dam-management program that is compatible with glass eel migration

European eel (Anguilla anguilla): prediction of spawner escapement from continental population parameters

This paper describes the assessment of silver European eel (Anguilla anguilla) escapement based on a “sedentary” population fraction analysis in a 60-km2 watershed of northern Brittany (France). Downstream migration fluxes were monitored using eel traps and related to environmental factors. Intensive electrofishing and fyke-net fishing were conducted to assess eel biomass, densities, and population structure. A total of 564 eels, including 81 silver eels, were PIT tagged. In 1996, 616 eels were caught in the catchment including 68 silver eels (11%). During the following downstream migration period, 12 of the PIT-tagged silver eels, among a total of 678, were recaptured in the downstream traps. Seven were recaptured in the catchment in 1997. It was shown that (i) only about 20% of the silver eels present in the catchment emigrated during the following year, (ii) 12% stayed in the catchment including two (3.4%) that recovered yellow eel characteristics, and (iii) the other eels either died or settled in the catchment but were not recaptured. It was also estimated that 2% (650 eels) of the population (34 000 eels) among 3000 silver eels considered “emigration candidates” emigrated each year

Spatial distribution of an eel population (Anguilla anguilla L.) in a small coastal catchments of northern Brittany (France). Consequences hydraulic works.

The Frémur is a 60 km2 catchment of Brittany where many hydraulic works (dams, weirs, gauging structures, etc.) have reduced the recruitment by elvers and glass eels since at least 50 years. In 1992, an eel lift was built on the main dam (14 m high) and in 1996, two other dams (5 m high) located downstream were equipped with eel passes to improve upstream migration. In 1995, before the construction of the passes, eel population parameters (density, biomass and size distribution) were assessed at the scale of the whole watershed by electrofishing (removal method) in 33 stations. The average biomass was high (19 g/m2 ) despite the numerous physical obstructions. However, there was an accumulation of eels downstream many hydraulic works and very low densities immediately upstream. Moreover, downstream the first obstruction, at 2 km from the sea, the population is dominated by boot lace eels and elvers (< 100 mm), whereas this size class is absent in upstream reaches. These results suggest that the standing capacity of the watershed is not reached and that the population could be enhanced in the next years by the recently installed eel passes

Escapement of a silver-phase eel population, Anguilla anguilla, determined from fishery in a Mediterranean lagoon (Or, France)

Escapement of silver eels from a Mediterranean lagoon was estimated by a capture–tagging–recapture and automated tag-reading study. The population of silver-phase eels in the lagoon was estimated to be 13.2 kg ha21, with an escapement rate from the commercial fishery of 76.8%

Perceptions of U.S. and Canadian maple syrup producers toward climate change, its impacts, and potential adaptation measures

The production of maple syrup is an important cultural and economic activity directly related to the climate of northeastern North America. As a result, there are signs that climate change could have negative impacts on maple syrup production in the next decades, particularly for regions located at the southern margins of the sugar maple (Acer saccharum Marsh.) range. The purpose of this survey study is to present the beliefs and opinions of maple syrup producers of Canada (N = 241) and the U.S. (N = 113) on climate change in general, its impacts on sugar maple health and maple syrup production, and potential adaptation measures. Using conditional inference classification trees, we examined how the socio-economic profile of respondents and the geographic location and size of respondents’ sugar bushes shaped the responses of survey participants. While a majority (75%) of respondents are confident that the average temperature on Earth is increasing, less than half (46%) believe that climate change will have negative impacts on maple syrup yield in the next 30 years. Political view was a significant predictor of these results, with respondents at the right right and center-right of the political spectrum being less likely to believe in climate change and less likely to anticipate negative effects of climate change on maple syrup production. In addition, 77% of the participants indicated an interest in adopting adaptation strategies if those could increase maple syrup production. This interest was greater for respondents using vacuum tubing for sap collection than other collection methods. However, for many respondents (particularly in Canada), lack of information was identified as a constraint limiting adaptation to climate change.SL and AP were partly funded by the CICan Career-Launcher Internship program. AA was supported by Spanish Government through the Juan de la Cierva fellowship program (IJCI- 2016-30049)

Can the intake of antiparasitic secondary metabolites explain the low prevalence of hemoparasites among wild Psittaciformes?

Background: Parasites can exert selection pressure on their hosts through effects on survival, on reproductive success, on sexually selected ornament, with important ecological and evolutionary consequences, such as changes in population viability. Consequently, hemoparasites have become the focus of recent avian studies. Infection varies significantly among taxa. Various factors might explain the differences in infection among taxa, including habitat, climate, host density, the presence of vectors, life history and immune defence. Feeding behaviour can also be relevant both through increased exposure to vectors and consumption of secondary metabolites with preventative or therapeutic effects that can reduce parasite load. However, the latter has been little investigated. Psittaciformes (parrots and cockatoos) are a good model to investigate these topics, as they are known to use biological control against ectoparasites and to feed on toxic food. We investigated the presence of avian malaria parasites (Plasmodium), intracellular haemosporidians (Haemoproteus, Leucocytozoon), unicellular flagellate protozoans (Trypanosoma) and microfilariae in 19 Psittaciformes species from a range of habitats in the Indo-Malayan, Australasian and Neotropical regions. We gathered additional data on hemoparasites in wild Psittaciformes from the literature. We considered factors that may control the presence of hemoparasites in the Psittaciformes, compiling information on diet, habitat, and climate. Furthermore, we investigated the role of diet in providing antiparasitic secondary metabolites that could be used as self-medication to reduce parasite load. Results: We found hemoparasites in only two of 19 species sampled. Among them, all species that consume at least one food item known for its secondary metabolites with antimalarial, trypanocidal or general antiparasitic properties, were free from hemoparasites. In contrast, the infected parrots do not consume food items with antimalarial or even general antiparasitic properties. We found that the two infected species in this study consumed omnivorous diets. When we combined our data with data from studies previously investigating blood parasites in wild parrots, the positive relationship between omnivorous diets and hemoparasite infestation was confirmed. Individuals from open habitats were less infected than those from forests. Conclusions: The consumption of food items known for their secondary metabolites with antimalarial, trypanocidal or general antiparasitic properties, as well as the higher proportion of infected species among omnivorous parrots, could explain the low prevalence of hemoparasites reported in many vertebrates

Développement d'un actionneur différentiel élastique

Ce mémoire présente les travaux effectués pour le développement d'un actionneur différentiel élastique (ADE) destiné à la mise en opération des bras tenseurs de la plate-forme robotique AZIMUT 2 . Un ADE est un nouveau type d'actionneur dit"élastique" développé par l'auteur.Ce type d'actionneur ressemble aux actionneurs sériels élastiques (ASE) inventés il y a une dizaine d'années [58]. Comme pour les ASE, les ADE sont des actionneurs de haute performance essentiellement pour les deux caractéristiques suivantes: (1) leur capacité de pouvoir contrôler avec précision leur état cinétique (couple produit); (2) leur faible impédance mécanique de sortie en boucle ouverte. L'originalité du mécanisme d'ADE repose sur la disposition des composantes constituant l'actionneur. Cette nouvelle configuration de composantes permet de réduire l'espace occupé par l'actionneur et par le fait même simplifier son intégration aux systèmes robotiques dont celui de la plate-forme AZIMUT 2 . Lorsqu'ils seront intégrés aux systèmes de locomotion à chenilles de la plate-forme AZIMUT 2 , les ADE permettront de contrôler avec précision et de façon sécuritaire les forces d'interaction présentes entre la plate-forme et l'environnement tout-terrain sur lequel elle est destinée à se déplacer.Ce mémoire propose un modèle analytique de prévision de performances de l'actionneur validé par une simulation sous l'environnement DYMOLA. De plus, les démarches entreprises pour caractériser le fonctionnement de l'actionneur en boucle ouverte sont également présentées. Ces démarches ont démontré la nécessité de développer davantage le modèle analytique de prévision de performances en y intégrant les phénomènes non-linéaires se produisant dans le réducteur de l'actionneur. Enfin, les travaux présentés confirment que l'usage d'ADE pour la mise en fonction des bras tenseurs de la plate-forme AZIMUT 2 est une solution appropriée et que le développement de ce nouveau type d'actionneur mérite d'être poursuivi

Développement d'un actionneur différentiel élastique

Ce mémoire présente les travaux effectués pour le développement d'un actionneur différentiel élastique (ADE) destiné à la mise en opération des bras tenseurs de la plate-forme robotique AZIMUT 2 . Un ADE est un nouveau type d'actionneur dit"élastique" développé par l'auteur.Ce type d'actionneur ressemble aux actionneurs sériels élastiques (ASE) inventés il y a une dizaine d'années [58]. Comme pour les ASE, les ADE sont des actionneurs de haute performance essentiellement pour les deux caractéristiques suivantes: (1) leur capacité de pouvoir contrôler avec précision leur état cinétique (couple produit); (2) leur faible impédance mécanique de sortie en boucle ouverte. L'originalité du mécanisme d'ADE repose sur la disposition des composantes constituant l'actionneur. Cette nouvelle configuration de composantes permet de réduire l'espace occupé par l'actionneur et par le fait même simplifier son intégration aux systèmes robotiques dont celui de la plate-forme AZIMUT 2 . Lorsqu'ils seront intégrés aux systèmes de locomotion à chenilles de la plate-forme AZIMUT 2 , les ADE permettront de contrôler avec précision et de façon sécuritaire les forces d'interaction présentes entre la plate-forme et l'environnement tout-terrain sur lequel elle est destinée à se déplacer.Ce mémoire propose un modèle analytique de prévision de performances de l'actionneur validé par une simulation sous l'environnement DYMOLA. De plus, les démarches entreprises pour caractériser le fonctionnement de l'actionneur en boucle ouverte sont également présentées. Ces démarches ont démontré la nécessité de développer davantage le modèle analytique de prévision de performances en y intégrant les phénomènes non-linéaires se produisant dans le réducteur de l'actionneur. Enfin, les travaux présentés confirment que l'usage d'ADE pour la mise en fonction des bras tenseurs de la plate-forme AZIMUT 2 est une solution appropriée et que le développement de ce nouveau type d'actionneur mérite d'être poursuivi

Metathetical Redox Reaction of (Diacetoxyiodo)arenes and Iodoarenes

The oxidation of iodoarenes is central to the field of hypervalent iodine chemistry. It was found that the metathetical redox reaction between (diacetoxyiodo)arenes and iodoarenes is possible in the presence of a catalytic amount of Lewis acid. This discovery opens a new strategy to access (diacetoxyiodo)arenes. A computational study is provided to rationalize the results observed

Catadromous migration dynamics of European eel (Anguilla anguilla, L.) in a dammed catchment.

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