2,417 research outputs found
Lamotte, M. et Bourlière, F. (Editeurs). — Problèmes d’écologie : Structure et fonctionnement des écosystèmes limniques. Masson, Paris, 1983
No full textCrivelli Alain Jean. Lamotte, M. et Bourlière, F. (Editeurs). — Problèmes d’écologie : Structure et fonctionnement des écosystèmes limniques. Masson, Paris, 1983. In: Revue d'Écologie (La Terre et La Vie), tome 39, n°4, 1984. pp. 480-481
Potts, G.W. and Wotton, R.J. (Editors). — Fish reproduction. Strategies and tactics. Academic Press, London, 1984
No full textCrivelli Alain Jean. Potts, G.W. and Wotton, R.J. (Editors). — Fish reproduction. Strategies and tactics. Academic Press, London, 1984. In: Revue d'Écologie (La Terre et La Vie), tome 41, n°2-3, 1986. p. 277
Conséquences des changements hydrologiques sur le fonctionnement biologique d’une lagune
No full textGrillas Patrick, Charpentier Anne, Chauvelon Philippe, Crivelli Alain Jean, Sandoz Alain, Lescuyer F., Coulet Eric. Conséquences des changements hydrologiques sur le fonctionnement biologique d’une lagune . In: Revue d'Écologie (La Terre et La Vie), tome 59, n°1-2, 2004. p. 367
Mr Alain Elkann Author and Journalist Italian Republic
No full textVisit by Mr Alain Elkann Author and Journalist Italian Republi
Translocation of stream-dwelling salmonids in headwaters: insights from a 15-year reintroduction experience
No full textTranslocation programs are a common strategy to increase the number of viable populations of threatened freshwater fishes. Yet, only in a minority of cases the success or failure of translocations has been assessed through a quantitative analysis of demographic traits, compensatory responses, lifehistories and population dynamics of the threatened species. A paradigmatic case a translocation program combining both management- and research-oriented activities is represented by the Marble Trout Conservation Program, which started in 1993 in the upper reaches of the Soca, Idirjca and Baca river basins (Slovenia) for the conservation of stream-dwelling marble trout Salmo marmoratus. In order to enhance the viability of the species, two new populations were created in 1996 by stocking 500 marble trout aged 1? in previously fishless streams (Gorska and Zakojska) within the core habitat of the species. The new populations have been systematically monitored for 15 years by individually tagging and sampling marble trout. Our analyses show that deterministic extinction of marble trout populations are unlikely and that highmagnitude environmental stochasticity (i.e., severe floods) is the only main cause of local population extinction, despite the high resilience to flood-induced massive mortalities exhibited by marble trout through compensatory mechanisms (e.g., relaxation of density-dependent body growth and survival at low densities). Fishless headwaters, probably characterized by a history of recurrent severe floods, should not be considered as candidate sites for the creation of new populations. Fewer individuals than originally reintroduced (i.e., 500 fish aged 1? in each stream) might be sufficient to establish viable populations, since compensatory mechanisms are likely to regulate population size around stream carrying capacity in a few years. Besides enhancing the species viability, translocation programs can provide an excellent framework for the estimation of ecological traits (e.g., life-histories, demography, population dynamics etc.), identify potential vulnerabilities and thus guide well-formed management actions for the threatened species
A demographic model for the conservation and management of the European eel: an application to a Mediterranean coastal lagoon
Get PDFInternational audienceWe present a general size and age-structured demographic model of the continental phase of catadromous eels' life cycle, allowing for the incorporation of (i) fluctuations of juvenile recruitment, (ii) density-dependent settlement and sex determination, (iii) plastic body growth and sexual dimorphism, and (iv) vital rates driven by body size rather than age. The model can be used to assess (i) standing stock, (ii) fishing yield, and (iii) spawner production under different recruitment and management scenarios. We demonstrate the model by applying it to a European eel stock (Camargue lagoons, southern France) that was continuously monitored for 17 years (1993-2009). Results indicate that the upper limit to settlement in the Camargue water system is ~419 eels ha ─1 per year. A balanced sex ratio occurs for a settlement of ~94 eels ha ─1 , shifting towards males at higher densities. Catchability is higher in adult silver eels than in sub-adult yellow eels, possibly due to behavioural differences. Estimated standing stock ranged between 7 and 19 kg ha ─1. Fishing yield was 5-7 kg ha ─1 per year, while spawner escapement ranged between 0 and 13 kg ha ─1 per year (<30% of what would occur in the absence of fishing and obstacles to migration). How to cite : Bevacqua D., Melià P., Schiavina M., Crivelli A.J., De Leo G.A., Gatto M. 2019. A demographic model for the conservation and management of the European eel: an application to a Mediterranean coastal lagoon
Within- and among-population variation in vital rates and population dynamics in a variable environment
No full textUnderstanding the causes of within- and among-population differences in vital rates, life histories, and population dynamics is a central topic in ecology. To understand how within- and among-population variation emerges, we need long-term studies that include episodic events and contrasting environmental conditions, data to characterize individual and shared variation, and statistical models that can tease apart shared and individual contribution to the observed variation. We used long-term tag-recapture data to investigate and estimate within- and among-population differences in vital rates, life histories, and population dynamics of marble trout Salmo marmoratus, an endemic freshwater salmonid with a narrow range. Only ten populations of pure marble trout persist in headwaters of Alpine rivers in western Slovenia. Marble trout populations are also threatened by floods and landslides, which have already caused the extinction of two populations in recent years. We estimated and determined causes of variation in growth, survival, and recruitment both within and among populations, and evaluated trade-offs between them. Specifically, we estimated the responses of these traits to variation in water temperature, density, sex, early life conditions, and extreme events. We found that the effects of population density on traits were mostly limited to the early stages of life and that growth trajectories were established early in life. We found no clear effects of water temperature on vital rates. Population density varied over time, with flash floods and debris flows causing massive mortalities (>55% decrease in survival with respect to years with no floods) and threatening population persistence. Apart from flood events, variation in population density within streams was largely determined by variation in recruitment, with survival of older fish being relatively constant over time within populations, but substantially different among populations. Marble trout show a fast to slow continuum of life histories, with slow growth associated with higher survival at the population level, possibly determined by food conditions and age at maturity. Our work provides unprecedented insight into the causes of variation in vital rates, life histories, and population dynamics in an endemic species that is teetering on the edge of extinction
Trade-offs between accuracy and interpretability in von Bertalanffy random-effects models of growth
No full textBetter understanding of variation in growth will always be an important problem in ecology. Individual variation in growth can arise from a variety of processes; for example, individuals within a population vary in their intrinsic metabolic rates and behavioral traits, which may influence their foraging dynamics and access to resources. However, when adopting a growth model, we face trade-offs between model complexity, biological interpretability of parameters, and goodness of fit. We explore how different formulations of the von Bertalanffy growth function (vBGF) with individual random effects and environmental predictors affect these trade-offs. In the vBGF, the growth of an organism results from a dynamic balance between anabolic and catabolic processes. We start from a formulation of the vBGF that models the anabolic coefficient (q) as a function of the catabolic coefficient (k), a coefficient related to the properties of the environment (γ) and a parameter that determines the relative importance of behavior and environment in determining growth (ψ). We treat the vBGF parameters as a function of individual random effects and environmental variables. We use simulations to show how different functional forms and individual or group variability in the growth function's parameters provide a very flexible description of growth trajectories. We then consider a case study of two fish populations of Salmo marmoratus and Salmo trutta to test the goodness of fit and predictive power of the models, along with the biological interpretability of vBGF's parameters when using different model formulations. The best models, according to AIC, included individual variability in both k and γ and cohort as predictor of growth trajectories, and are consistent with the hypothesis that habitat selection is more important than behavioral and metabolic traits in determining lifetime growth trajectories of the two fish species. Model predictions of individual growth trajectories were largely more accurate than predictions based on mean size-at-age of fish. Our method shares information across individuals, and thus, for both fish populations investigated, allows using a single measurement early in the life of individual fish or cohort to obtain accurate predictions of lifetime individual or cohort size-at-age
Données préliminaires sur la communauté d’amphibiens de la Réserve Naturelle de Roque-Haute dans le sud de la France
No full textSeven species of amphibians have been recorded at the Roque-Haute Nature Reserve, two newt species : Triturus marmoratus and T. helveticus and five frog species : Hyla meridionalis, Pelodytes punctatus, Pelobates cultripes, Bufo calamita, Rana perezi. Many of these species have a geographic distribution restricted to southern France and the Iberian Peninsula, and are considered as vulnerable. Only 25% of the pools of the Roque-Haute Nature Reserve are used for amphibian reproduction. The larval period lasts from autumn to the end of the following summer. Two species have a reproduction in autumn as well as in spring : Pelodytes punctatus and Pelobates cultripes. More studies are needed on the demography and the genetics of these amphibian populations in order to assess their viability and to ensure their conservation.Sept espèces d’amphibiens ont été dénombrées dans la Réserve Naturelle de Roque-Haute, deux urodèles : Triturus marmoratus et T. helvéticas et cinq anoures : Hyla meridionalis, Pelodytes punctatus, Pelobates cultripes, Bufo calamita, Rana perezi. Beaucoup de ces espèces ont une distribution géographique restreinte au sud de la France et à la Péninsule ibérique et la plupart sont considérées comme vulnérables. Seulement 25% des mares de Roque-Haute sont utilisées par les amphibiens pour leur reproduction. La période larvaire dure de l’automne à l’été suivant. Deux espèces ont à la fois une reproduction automnale et printanière, ce sont Pelodytes punctatus et Pelobates cultripes. De nouvelles études sur le fonctionnement démographique et la génétique de ces populations d’amphibiens sont nécessaires afin d’évaluer leur viabilité et d’assurer leur protection.Jakob Christiane, Veith Michael, Seitz Alfred, Crivelli Alain J. Données préliminaires sur la communauté d’amphibiens de la Réserve Naturelle de Roque-Haute dans le sud de la France. In: Ecologia mediterranea, tome 24 n°2, 1998. pp. 235-240
Résister à la normalisation des conduites : Entretien avec Roland Gori, propos recueillis par Alain Policar
No full textCo-initiator of the call of calls denouncing the ideology of a neuroeconomic man in whose name the current reforms break and redial our jobs and tasks of care, social works, education, research, justice, information and culture, the author analyzes mainly the psychiatric knowledge and practice as facts of civilization.Co-initiateur de l'Appel des appels qui dénonce l'idéologie d'un «homme économique» au nom de laquelle les réformes actuelles défont et recomposent les métiers et les missions du soin, du travail social, de l'éducation, de la recherche, de la justice, de l'information et de la culture, l'auteur analyse ici principalement les savoirs et les pratiques psychiatriques comme «des faits de civilisation».Policar Alain, Gori Roland. Résister à la normalisation des conduites : Entretien avec Roland Gori, propos recueillis par Alain Policar. In: Raison présente, n°171, 3e trimestre 2009. Savoir, connaitre, agir. pp. 87-94
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