Influence des élevages extensifs en étang sur les rivièrese

Si de nombreux travaux ont porté sur l'influence des piscicultures intensives sur les rivières, on s'est peu intéressé aux conséquences des nombreuses créations de plan d'eau sur le milieu. Le but de cet article est de présenter en s'appuyant sur des exemples précis les différentes modifications apportées sur le milieu par une surface en eau d'élevage extensif.Les aspects hydrologiques sont peu importants. Les changements physico-chimiques ont par contre de nombreuses conséquences, directes et indirectes :- la température : le réchauffement estival agit sur les réactions chimiques, l'équilibre des biocénoses, la pathologie des poissons,- le potentiel hydrogène, très variable en cas de faible dureté,- l'oxygénation, liée à la température dont le déficit agit directement sur la faune pisciaire,- la fertilisation par l'azote et les phosphates,- les matières en suspension : action surtout manifeste lors des vidanges, directe sur le colmatage des frayères, indirecte sur la structure des communautés floristique et faunistique.Le repeuplement des rivières par les poissons d'étang est fréquent. Les conséquences vont du déséquilibre faunistique à l'introduction d'espèces indésirables ou nuisibles. Dans l'ensemble, on note un impact négatif sur les eaux courantes, particulièrement sur les rivières à salmonidés (1ère catégorie). Sur les cours d'eau de 2e catégorie, l'impact est toujours plus faible et on peut noter une action bénéfique due au lagunage.Une hiérarchisation des influences est donnée en tenant compte du type de plan d'eau et de son mode de gestion.Although many studies relate to the influence of fish farming on rivers, little interest has been given to the environmental impact of artificial ponds. The aim of this article is to show through precise examples the various alterations in the environmental system caused by extensive fish breeding farms.Hydrological aspectsEven in the absence of any breeding, the presence of a water surface brings about variations in the local water balance.- losses due to infiltration may increase through the drilling of an impermeable substratum when digging the pond, but new springs are often observed, resulting in an inscreased stream flow.- fosses due to evaporation vary according to local climate and environment.Pond dams sometimes act as buffers against floods.Influences can only be significant under particular conditions : regional temperature and humidity and the nature of the substratum.Physico-chemical aspectsDuring the filling period, one of the greatest risks is the rise in temperature. Even though the latter only occasionally reaches 10 % of its initial value, the effects are numerous :- reduction of dissolved oxygen content and acceleration of microbial processes of aerobic decomposition.- effect on biocenosis : a 3 to 4 °C rise in average maximal temperature may result in a typological change in the streams normally hosting Salmonidae. The disappearance of benthic Invertebrata may be observec as well as their replacement by groups whose development is stimulated by temperature : e.g. Mollusca and Worms.- effect on pollution : a 1 °C rise in temperature, from pH to basic values results in a growing concentration in ammoniacal nitrogen which turns out to be toxic. On the other band, a possible favourable affect upon second class fish breeding streams must be noted. Eutrophization and enhancement of the environment also occur in addition to an accelerated gametogenesis in some species. In the late summer, this results gametogenesis in some species. In the late summer, this results in larger fish an, consequently, increased chances of survival lacer. An EEC rule has set the tolerance limits of temperature rise according to the type of river (table 4).If It remains sustined, the discharge of suspended matter may also have various influences. Except for accidents, the risk is slight, measured values are generally inferior to EEC standards. However, it is essential to consider that discharges minerals and organic compounds such as some phytosanitary products (Lindane, Atrazine) likely to cause immediate or delayed toxic effects.The creation of a pond is clearly a cause of instability in the composition of water immediately downstream, especially regarding the pH and, indirectly, NH3 content. This risk is all the greater since restituted water is the result of overflow. As for oxygen, the problem may be assessed differently, according to the mode of restitution; overflow may improve oxygenation whereas overflow caused by an emptying device may cause deoxygenation. Whatever the mode of restitution, downstream water is enriched with soluble and particulate organic matter which can promote bacterial development and oxygen intake.Finally, it is worth noting that pend phytoplankton is likely to culture the downstream river, all the more intensely since the sluggishness of water flow will be stopped up.The impact will depend upon the kind of pond involved : a « ballast tank » unconnected with the stream will have a lesser influence than a derivated pond. Since maximal impact will occur in the discharging channel before reaching the stream's downstream zone. The influence will be much more harmful to Salmonidae streams which are more sensitive to a reduction in dissolved oxygen. The imbalance will be heightened by fish losses which are likely to happen, since all species must compete with the surrounding fauna and will be favored by environ mental imbalance.During the emptying operation, besides the circulation of elements trapped by sediment, the addition of suspended matter will involve e high risk for fishbreeding downstream from the discharge. If, during the draining operation, discharge volume is lower than EEC standards (25 mg/l), the emptying operation causes content to reach more than 100 mg/l, with immediate or delayed side affects.The most direct harm done is asphyxiation of most fish under certain circumstances. This is heightened is a real risk of bringing about a rise in temperature : passing from a Salmonidae to a Cyprinidae environment both through disruption of the inverterbrata fauna, and sealing of the spawining places dug in the streambed gravel at emptying periods. The risk of a reduction in fauna varies and invertebrata biomass should also be brought up.Whenever fish are discharged, repopulation of the river usually results. In this case again, the affects will be negative for Salmonidae streams or intermediate-type water in which the replacement and introduction of new species can occur. Everything will depend upon the breeding carried out in the pond.In 2nd-category fish-breeding rivers, only a reinforcement of population and possibly a diversification of species will be observed.As a conclusion, all artificial ponds have a negative impact upon freshwater especially in 1st-category fish farming rivers : e.g. changes in physico-chemical characteristics, introduction of species. This impact occurs during the filling period of the pond (variation in temperature) and the emptying operation (various discharges). In some cases, favourable consequences can be observed (table 1) : natural creation of a lagoon with trapping of elements in solution (phosphates, nitrogen). Moreover, the presence of alcalinity is stronger because of water sediment transfers, as is pH, showing a better fish farming potential.The impact on freswater depends upon the type of pond and the method used for emptying

The High-Superior-Tension Technique: Evolution of Lipoabdominoplasty

Because abdominoplasty is associated with complications such as seroma and necrosis as well as epigastric bulging and a suprapubic scar located too high, the demand for this procedure is not as high as it otherwise might be. However, although these negative effects were common many years ago, their incidence has decreased dramatically with modern abdominoplastic techniques. One approach using a combination of abdominoplasty and liposuction or lipoabdominoplasty has resolved many of the problems faced with earlier techniques, offering aesthetically pleasing results and excellent reliability. The keys to successful lipoabdominoplasty, first developed as the high-superior-tension technique, are extensive liposuction, preservation of lymphatic trunks, preaponeurotic epigastric dissection, major muscle fascia plication, two high-tension paraumbilical sutures, hypogastric tension sutures, and closure of the dead spaces. The most recent updates to this technique are described in this article

Biologie et écologie du Lérot Eliomys quercinus L. dans les Hautes-Alpes

Dans la région de Rriançon (Hautes-Alpes), le Lérot Eliomys quercinus est un des principaux constituants de la faune de Ron geurs de tous les types de forêts. La sortie d’hibernation se produit à la tin de la première quinzaine de mai. Les individus sont aussitôt sexuellement actifs, les mises bas ont lieu de la mi-juin à la tin juillet. L’entrée en hibernation débute à la mi-septembre et intéresse d’abord les adultes. Du fait de la faible durée de la vie active, il ne semble pas y avoir d’estivation. La saison de reproduction étant bien loca lisée dans le temps, il est facile d’estimer l’âge des individus et de tracer leur courbe de croissance. Il est à remarquer que la croissance n’est pas terminée lors de l’entrée en hibernation, et qu’elle se poursuit au printemps suivant. Les types de forêts les plus fréquentées sont les boisements mixtes, Pin sylvestre - Mélèze et Feuillus - Mélèze de l’étage mon tagnard (1 400 à 1 700 m d’altitude). Les facteurs du milieu les plus favorables sont la présence de substrat rocheux et d’une végétation herbacée claire accompagnée d’arbrisseaux nains. Le régime alimentaire est en grande partie composé d’insec tes, surtout de larves de Lépidoptères.Around Briançon, Hautes-Alpes, France, the Garden dormouse Eliomys quercinus is one of the most common rodents in all types of forests. When they arouse from hibernation these animals are immediately active sexually. Parturition takes place from mid-June to the end of July. Dormice enter hibernation in mid- September, first the adult animals and then the younger ones. Owing to the short lenght of their active life, there is apparently no estivation in this part of France. The breeding season is temporally well defined. It is therefore easy to estimate the age of the animals and to establish their growth curve. Sexual maturity is not achieved when young of the year enter hibernation ; they do not become mature before the next spring. Garden dormice live usually in mixed forests of Pine (Pinus sylvestris) and Larch, and of Larch and deciduous trees, at an altitude of 1 400-1 700 m above sea-level. The most important parameters of their environment are the presence of a rocky substrate and of a sparse grass layer with dwarf shrubs. Garden dormice are mostly insectivorous and are particularly fond of caterpillars and pupae

Standardisation des piégeages en ligne pour quelques espèces de rongeurs

Une méthode standardisée de piégeage en ligne a été expé rimentée pour les rongeurs suivants : Eliomys quercinus, Pitymys multiplex, Clethrionomys glareolus, Microtus arvalis, Apodemus sylvaticus et Taterillus pygargus. Toutes ces expériences confir ment l’idée générale qu’il existe une relation de proportionnalité entre la densité de population et le nombre de captures en un temps donné sur une longueur donnée de ligne. Mais cette relation dépend étroitement des caractères de l’activité des Rongeurs. Il est montré que le coefficient de ligne est une fonction puissance négative de la moyenne des distances entre recaptures successives de la catégorie considérée. Des coefficients de ligne d’usage pra tique sont indiqués.A standard line trapping technique has been tested with the following Rodent species : Eliomys quercinus, Pitymys multiplex, Clethrionomys glareolus, Microtus arvalis, Apodemus sylvaticus and Taterillus pygargus. A proportional relation occurs between population density and number of catches during a given time- period, along a given length of trap-line. However this rela tionship depends also on the activity pattern and daily movements of the species studied. The « Line coefficient » is a negative power function of the average distance between successive catches (« average-D »)

The adaptive optics simulation analysis tool(kit) (AOSAT)

AOSAT is a python package for the analysis of single-conjugate adaptive optics (SCAO) simulation results. Python is widely used in the astronomical community these days, and AOSAT may be used stand-alone, integrated into a simulation environment, or can easily be extended according to a user's needs. Standalone operation requires the user to provide the residual wavefront frames provided by the SCAO simulation package used, the aperture mask (pupil) used for the simulation, and a custom setup file describing the simulation/analysis configuration. In its standard form, AOSAT's "tearsheet" functionality will then run all standard analyzers, providing an informative plot collection on properties such as the point-spread function (PSF) and its quality, residual tip-tilt, the impact of pupil fragmentation, residual optical aberration modes both static and dynamic, the expected high-contrast performance of suitable instrumentation with and without coronagraphs, and the power spectral density of residual wavefront errors. AOSAT fills the gap between the simple numerical outputs provided by most simulation packages, and the full-scale deployment of instrument simulators and data reduction suites operating on SCAO residual wavefronts. It enables instrument designers and end-users to quickly judge the impact of design or configuration decisions on the final performance of down-stream instrumentation.EPI

Galaxies in Southern Bright Star Fields I. Near-infrared imaging

As a prerequisite for cosmological studies using adaptive optics techniques, we have begun to identify and characterize faint sources in the vicinity of bright stars at high Galactic latitudes. The initial phase of this work has been a program of K_s imaging conducted with SOFI at the ESO NTT. From observations of 42 southern fields evenly divided between the spring and autumn skies, we have identified 391 additional stars and 1589 galaxies lying at separations 60" from candidate guide stars in the magnitude range 9.0 R 12.4. When analyzed as a "discrete deep field" with 131 arcmin^2 area, our dataset gives galaxy number counts that agree with those derived previously over the range 16 K_s 20.5. This consistency indicates that in the aggregate, our fields should be suitable for future statistical studies. We provide our source catalogue as a resource for users of large telescopes in the southern hemisphere.Comment: 10 pages, 7 figures, accepted by A&A; Table 3 is available at http://www.rzg.mpg.de/~ajb/data.html pending upload to CD

Determination of masses of the central black holes in NGC524 and NGC2549 using Laser Guide Star Adaptive Optics

[abridged] We present observations of NGC524 and NGC2549 with LGS AO obtained at GEMINI North telescope using the NIFS IFU in the K band. The purpose of these observations, together with previously obtained observations with the SAURON IFU, is to determine the masses (Mbh) of the supermassive black holes (SMBH). The targeted galaxies were chosen to have central light profiles showing a core (NGC524) and a cusp (NGC2549), to probe the feasibility of using the galaxy centre as the NGS required for LGS AO. We employ an innovative `open loop' technique. The data have spatial resolution of 0.23" and 0.17" FWHM, showing that high quality LGS AO observations of these objects are possible. We construct axisymmetric three-integral dynamical models which are constrained with both the NIFS and SAURON data. The best fitting models yield Mbh=(8.3 +2.7 -1.3) x 10^8 Msun for NGC524 and Mbh=(1.4 +0.2 -1.3) x 10^7 Msun for NGC2549 (all errors are at the 3 sigma CL). We demonstrate that the wide-field SAURON data play a crucial role in the M/L determination increasing the accuracy of M/L by a factor of at least 5, and constraining the upper limits on Mbh. The NIFS data are crucial in constraining the lower limits of Mbh and in combination with the large scale data reducing the uncertainty by a factor of 2 or more. We find that the orbital structure of NGC524 shows significant tangential anisotropy, while at larger radii both galaxies are consistent with having almost perfectly oblate velocity ellipsoids. Tangential anisotropy in NGC524 coincides with the size of SMBH sphere of influence and the core region in the light profile. We test the accuracy to which Mbh can be measured using seeings obtained from typical LGS AO observations, and conclude that for a typical conditions and Mbh the expected uncertainty is of the order of 50%.Comment: 19 pages, 14 figure