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Search Results: 1 - 10 of 73676 matches for " assemblage de poissons "
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Long-term changes in fish assemblage following the impoundments of the Three Gorges Reservoir in Hejiang, a protected reach of the upper Yangtze River Changements à long terme dans les assemblages de poissons en Hejiang, un bief protégé de la haute rivière Yangtsé, après mise en service du Barrage des Trois Gorges
Liu F.,Wang J.,Cao W.
Knowledge and Management of Aquatic Ecosystems , 2013, DOI: 10.1051/kmae/2013032
Abstract: The construction of the Three Gorges Reservoir (TGR) has seriously affected the fish assemblage in the impounded reaches. However, fish assemblage changes in the riverine zone remain poorly documented. In order to explore how upstream fish assemblage has responded to the successive impoundments of the TGR, fish investigations were conducted biannually in Hejiang, a protected reach of the upper Yangtze River, during the period from 1997 to 2011. Multivariate analysis revealed significant temporal differences in fish assemblage following the impoundments of the TGR. Prior to the impoundments, the fish assemblage appeared to be very diversified and very even. Immediately after the first and the second impoundment, the lotic species, such as Coreius guichenoti, Rhinogobio ventralis, Rhinogobio cylindricus and Coreius heterodon, became evidently dominant, due to their upstream migrations from the reservoir. However, two years after the third impoundment, the lotic species decreased dramatically, while lentic Hypophthalmichthys molitrix and Pelteobagrus vachelli became the new dominant species. Based on this and other studies, we can see the habitats of the riverine fish in the upper Yangtze River have been shrunk seriously because of the impoundments of the TGR. The cascade hydropower development in the lower Jinsha River will pose an accumulative effect on the aquatic environment in the mainstream of the upper Yangtze River. Free-flowing tributaries, such as the Chishui River, will play more important roles in fish conservation. La construction du réservoir des Trois Gorges (TGR) a sérieusement affecté l’assemblage de poissons dans les biefs aménagés. Cependant, les changements d’assemblage de poissons dans la zone lentique amont restent mal documentés. Afin d’explorer la fa on dont les assemblages de poissons en amont ont répondu aux remplissages successifs du TGR, des investigations piscicoles ont été menées deux fois par an dans Hejiang, un secteur protégé de la rivière Yangtsé amont, au cours de la période allant de 1997 à 2011. L’analyse multivariée a révélé d’importantes différences temporelles dans les peuplements de poissons après les remplissages successifs du TGR. Avant les retenues d’eau, l’assemblage de poissons semble être très diversifié et très équitable. Immédiatement après les mises en eau, les espèces lotiques, comme Coreius guichenoti, Rhinogobio ventralis, Rhinogobio cylindricus et Coreius heterodon sont devenues nettement dominantes, en raison de leur déplacement vers l’amont du réservoir. Cependant, deux ans après la troisième mise en
Assemblage Thinking and the City: Implications for Urban Studies  [PDF]
Hesam Kamalipour, Nastaran Peimani
Current Urban Studies (CUS) , 2015, DOI: 10.4236/cus.2015.34031
Abstract: The last decade has seen an increasing interest in the application of assemblage thinking, in geography, sociology, and urban studies. Different interpretations of the Deleuzian concept of assemblage give rise to the multiple articulations of the term in urban studies so far. This paper aims to review the recently published research on assemblage theory and explore the implications of assemblage thinking in urban studies. The study thus provides an overview of the most significant contributions in the area, including a succinct bibliography on the subject. The paper concludes that assemblage can be effectively adopted as a way of thinking in urban studies to provide a theoretical lens for understanding the complexity of the city problems by emphasising the relations between sociality and spatiality at different scales.
Impact of acadja fisheries on fish assemblages in Lake Nokoué, Benin, West Africa Impact des pêcheries en acadjas sur les assemblages de poissons du Lac Nokoué au Bénin, Afrique de l’Ouest
Niyonkuru C.,Lalèyè P.A.
Knowledge and Management of Aquatic Ecosystems , 2010, DOI: 10.1051/kmae/2010033
Abstract: Acadjas are artificial systems aimed at enhancing fish production by providing additional substrata for development of plants and animals upon which the fish will feed. This study aims to evaluate the impact of acadjas on fish assemblages and on conservation of the fish fauna diversity in Lake Nokoué in Benin. Between June 2003 and September 2004, experimental acadjas were installed and monitored. Fish samples were obtained from two areas of Lake Nokoué (Ganvié and Zogbo stations) within and without acadjas with the assistance of artisanal fishermen. Physico-chemical parameters were also measured inside and outside of the experimental acadjas in the same two stations. Twenty-five fish species belonging to 17 families were identified in acadjas out of a total of 51 species belonging to 34 families inventoried in 2001 at Lake Nokoué (i.e. 49% of the specific richness of the ichthyofauna). Fifty-six percent of fish fauna caught in acadjas are estuarine forms and represent 78% of all estuarine forms of Lake Nokoué in 2001. The analysis of variance showed that the specific richness of the acadjas varied significantly according to the station (p < 0.05), with a high specific richness in Zogbo station where acadjas are less abundant. Acadjas are selective for some fish species such as cichlids which represent 95% of the total numeric abundance and contribute about 90% of the total fish biomass. The high densities of acadjas could contribute to the reduction of the richness of fish fauna. Rational management could consist of reorganizing the surface areas of Lake Nokoué by preserving areas for other fish species that do not colonize acadjas. Les acadjas, ou parcs à poissons, sont des systèmes artificiels visant l’augmentation de la production de poisson en fournissant du substrat complémentaire pour le développement des plantes et animaux devant servir de nourriture aux poissons. Cette étude a pour objectif d’évaluer l’impact des acadjas sur les assemblages des poissons et la conservation de la diversité ichtyologique du lac Nokoué au Bénin. Ainsi, entre juin 2003 et septembre 2004, les acadjas expérimentaux ont été installés et suivis. Les échantillons de poissons ont été obtenus dans les deux stations (Ganvié et Zogbo) du lac Nokoué à l’intérieur et à l’extérieur des acadjas à l’aide des pêcheurs artisanaux. Les paramètres physico-chimiques ont été également mesurés à l’intérieur et à l’extérieur des acadjas expérimentaux des mêmes stations. Au total, 25 espèces de poissons appartenant à 17 familles ont été identifiées à l’intérieur des acadjas sur un total de
Fish assemblage structure in the Chishui River, a protected tributary of the Yangtze River Structure des communautés piscicoles de la rivière Chishui, un affluent protégé du fleuve Yangtzé
Wu J.,Wang J.,He Y.,Cao W.
Knowledge and Management of Aquatic Ecosystems , 2011, DOI: 10.1051/kmae/2011023
Abstract: This study aimed to characterize fish assemblage and evaluate environmental influence on fish distribution in the Chishui River, a protected tributary of the upper Yangtze River. Thirty-one sites regularly distributed in longitudinal profiles were sampled in April, 2007. Sixty-two fish species belonging to 3 orders, 8 families, and 52 genera were collected. Species richness and diversity significantly increased from upstream to downstream. Canonical correspondence analysis (CCA) highlighted five environmental variables (altitude, conductivity, dissolved oxygen, channel width and current velocity) significantly structuring fish assemblages in the Chishui River. Based on species distributions and fish-habitat relationships, conservation strategies were proposed for different reaches. Cette étude caractérise les communautés de poissons et évalue l’influence environnementale sur la distribution piscicole dans la rivière Chishui, un affluent protégé du fleuve Yangtzé. Trente-et-un sites régulièrement répartis sur le profil longitudinal ont été échantillonnés en avril 2007. Soixante-six espèces de poissons appartenant à 3 ordres, 8 familles et 52 genres ont été collectées. La richesse et la diversité spécifique augmentent significativement de l’amont vers l’aval. L’analyse canonique des correspondances (CCA) identifie cinq variables environnementales (altitude, conductivité, oxygène dissous, largeur du lit et vitesse du courant), structurant significativement les communautés de poissons dans la rivière Chishui. à partir des distributions spécifiques et des relations habitat-poisson, des stratégies de conservation sont proposées pour les différents biefs.
Water temperature modeling in the Garonne River (France) Modélisation de la température de l’eau de la Garonne (France)
Larnier K.,Roux H.,Dartus D.,Croze O.
Knowledge and Management of Aquatic Ecosystems , 2010, DOI: 10.1051/kmae/2010031
Abstract: Stream water temperature is one of the most important parameters for water quality and ecosystem studies. Temperature can influence many chemical and biological processes and therefore impacts on the living conditions and distribution of aquatic ecosystems. Simplified models such as statistical models can be very useful for practitioners and water resource management. The present study assessed two statistical models – an equilibrium-based model and stochastic autoregressive model with exogenous inputs – in modeling daily mean water temperatures in the Garonne River from 1988 to 2005. The equilibrium temperature-based model is an approach where net heat flux at the water surface is expressed as a simpler form than in traditional deterministic models. The stochastic autoregressive model with exogenous inputs consists of decomposing the water temperature time series into a seasonal component and a short-term component (residual component). The seasonal component was modeled by Fourier series and residuals by a second-order autoregressive process (Markov chain) with use of short-term air temperatures as exogenous input. The models were calibrated using data of the first half of the period 1988–2005 and validated on the second half. Calibration of the models was done using temperatures above 20 °C only to ensure better prediction of high temperatures that are currently at stake for the aquatic conditions of the Garonne River, and particularly for freshwater migrating fishes such as Atlantic Salmon (Salmo salar L.). The results obtained for both approaches indicated that both models performed well with an average root mean square error for observed temperatures above 20 °C that varied on an annual basis from 0.55 °C to 1.72 °C on validation, and good predictions of temporal occurrences and durations of three temperature threshold crossings linked to the conditions of migration and survival of Atlantic Salmon. La température de l’eau est un élément prépondérant pour l’étude de la qualité de l’eau et des écosystèmes. De nombreuses réactions chimiques et biologiques peuvent être influencées par la température qui impacte donc sur les conditions de viabilité et la distribution spatiale des espèces. Des modèles simples tels que les modèles statistiques peuvent être très utiles pour les gestionnaires et le management des ressources aquatiques. Cette étude visait à étudier la pertinence de deux modèles statistiques – le modèle basé sur la température d’équilibre et le modèle stochastique autorégressif avec facteurs externes – à modéliser les moyennes journalières de
Development of a fish-based index of biotic integrity (FIBI) to assess the quality of Bandama River in C te d’Ivoire* Développement d’un indice d’intégrité biotique basé sur le poisson pour évaluer la qualité du fleuve Bandama en C te d’Ivoire
Aboua B.R.D.,Kouamélan E.P.,N’Douba V.
Knowledge and Management of Aquatic Ecosystems , 2012, DOI: 10.1051/kmae/2012002
Abstract: The aim of this study was to develop effective tools based on fish assemblages, allowing the development of an effective assessment approach for the ecological status of running waters. Fish samples were collected using gill-nets with mesh sizes of 8, 10, 12, 14, 15, 18, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 and 80 mm. Forty sites were visited from October 2008 to September 2009 in the Bandama River. A large part of the data set on fish descriptors associated with environmental parameters was compiled from regional databases. For each of the fish assemblage descriptors, stepwise multiple linear regressions with habitat variables were carried out. The residuals of the models obtained were used as candidate metrics independent of natural environmental factors. Student t-tests used to compare each metric in reference and disturbed samples indicated significant difference (P < 0.05) for six metrics. The standard residuals of metrics selected were added to constitute the final index. This multimetric index of fish assemblage integrity could serve as a practical technical reference for conducting cost-effective biological assessments of lotic systems. Le but de cette étude était de développer un outil basé sur le peuplement de poissons qui permettrait une évaluation effective du statut des cours d’eau. Les poissons ont été récoltés à l’aide de filets maillants de maille : 8, 10, 12, 14, 15, 18, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 et 80 mm. 40 sites ont été visités durant un an (octobre 2008 à septembre 2009) sur le fleuve Bandama. Une grande partie des données sur les descripteurs de poissons, associée aux paramètres environnementaux, a été fournie à partir d’études déjà réalisées en Afrique. Pour chacun des descripteurs des peuplements de poissons, des relations ont été établies avec des variables environnementales, à partir de régressions linéaires multiples pas à pas. Les résidus de ces modèles ont été utilisés comme métriques susceptibles d’entrer dans la constitution d’un indice. Le test-t utilisé pour comparer les métriques entre prélèvements perturbés et prélèvement non perturbés indiquent une différence significative (P < 0,05) pour six métriques. Les résidus standards des métriques sélectionnées ont été additionnés pour constituer l’indice final. L’indice multi-paramétrique obtenu devrait être capable de fournir une évaluation pertinente de la qualité écologique des hydrosystèmes fluviaux.
Fish assemblage in a temperate estuary on the uruguayan coast: seasonal variation and environmental influence
Plavan, Alicia Acu?a;Passadore, Cecilia;Gimenez, Luis;
Brazilian Journal of Oceanography , 2010, DOI: 10.1590/S1679-87592010000400005
Abstract: the seasonal dynamics of the fish community in the pando estuary on the uruguayan coast were studied in relation to environmental sampled monthly between may 2002 and june 2003. individuals collected were identified, and classified into stages (juveniles, adults) and functional groups. relationships between community dynamics and environmental variables were evaluated using uni- and multivariate techniques. twenty-one species, mostly freshwater stragglers, estuarine and marine migrants were collected. the most abundant species were micropogonias furnieri, mugil platanus, paralichthys orbignyanus and brevoortia aurea and were represented by juveniles. the community varied seasonally with rapid shifts in spring and autumn associated with changes in temperature and salinity. significant correlations between abundance and temperature may be related to the timing of life cycle events. in this estuary, the salinity appears to play a key role in the functional structure and in the use of the habitat by juveniles. this is relevant for the definition of estuaries as nursery areas: this definition is context-dependent and is determined by the salinity conditions.
HUALFíN INKA: TECNOLOGíA LíTICA DE UN CENTRO ADMINISTRATIVO (CATAMARCA, ARGENTINA) (Hualfín Inka: lithic technology of an administrative center)
Julieta Lynch,Virginia Lynch
Arqueología Iberoamericana , 2011,
Abstract: Es bien sabido que el Imperio inca (Tawantinsuyu), a medida que se extendía, iba anexionando territorios y poblaciones muy disímiles unas de otras. Para ello, habría utilizado diversas tácticas políticas y económicas. A pesar de esta estrategia, la anexión de nuevos territorios habría producido algunos cambios estructurales en las poblaciones locales, que contaban con mecanismos sociales, políticos y económicos propios. En el presente trabajo, se intenta indagar acerca de la relación establecida entre los pobladores locales del valle de Hualfín (Catamarca, Argentina) y los objetivos planteados por el Imperio en dicha región. Para ello, se analizó el material lítico recuperado, tanto superficial como estratigráficamente, del sitio Hualfín Inka con el fin de reconstruir, junto con los resultados del análisis del resto de los materiales rescatados, la funcionalidad de este sitio y su relación con el paisaje sociopolítico para el período de ocupación incaica del Noroeste argentino. ENGLISH: It is well known that the Inca Empire (Tawantinsuyu), as it expanded, annexed new territories and populations very dissimilar to each other. For this reason, the Inca administration likely used diverse political and economical strategies. Due to this implementation policy, annexation would have caused certain structural changes in local populations that already had different social, political and economic characteristics. In this study we explore the relationship between local residents of Hualfín Valley (Catamarca, Argentina) and the objectives set by the Inca Empire in the region. For this purposes, we analyzed the lithic assemblage recovered from both surface and stratigraphic contexts from the site of Hualfín Inka. Based on the analysis of the lithic assemblage and that of other artifacts recovered at the site, our aim is to reconstruct the site’s function and its relationship to the sociopolitical landscape at the time of the Inca occupation of Northwest Argentina.
Influence of a shipwreck on a nearshore-reef fish assemblages off the coast of Rio de Janeiro, Brazil Influencia de un buque sumergido sobre agregaciones de peces asociados a un arrecife somero de la costa nordeste de Rio de Janeiro, Brasil
Eduardo Barros Fagundes-Netto,Luiz Ricardo Gaelzer,Ricardo Coutinho,Ilana R Zalmon
Latin american journal of aquatic research , 2011,
Abstract: The effect of the Orion shipwreck on fish assemblage distribution near the reef was studied to the northeast of Rio de Janeiro with six different fishing gears: gillnets, mid-water longlines, circular traps, rectangular traps, vertical longlines, and bottom trawling. The study consisted of a pre-monitoring survey four months before the shipwreck in the area (A) and in two control areas (B and C). After 36 months, a total of 56 species were caught in the Orion reef area, 49 in control area B and 59 in control area C. The similarity analysis, considering the number of fish caught during the nine surveys in the three study areas, clustered the pre-monitoring and first post-settlement surveys of the three sites. This occurred due to the low number of fish captured and the dominance of Trichiurus lepturus and Lagocephalus laevigatus. These results differed from all the other studies in the three areas due to the co-dominance of Ctenosciaena gracilicirrhus and Stephanolepis hispidus. Such spatial similarity shows the low influence of the Orion reef in the area after three years. Biomass values were 15% higher in the Orion reef area than in the control areas, representing an increase of up to 1.2 times in wet weight. The increment of fish communities is still insufficient for proposing sustainable fishery activity in the shipwreck area. The monitoring time (32 months) after the sinking of the Orion may be considered too short to assure that the wreckage had reached its maturity as an artificial reef, either as a fish attractor or producer. El efecto del buque sumergido Orion sobre la distribución de las comunidades de peces próximas al arrecife fue estudiado en el noreste de Rio de Janeiro utilizándose seis artes de pesca: red de enmalle, palangre pelágico, trampas circulares, trampas rectangulares, palangres y red de arrastre de fondo. El estudio consistió en una investigación premonitoreo, cuatro meses antes del naufragio en el area (A) y en dos areas control (B y C). Después de 36 meses, 56 especies fueron capturadas en el arrecife Orion, 49 en el area control B y 59 en el control C. Los análisis de similitud considerando el número de peces capturados durante las nueve campa as en las tres areas de estudio, agruparon las campa as de premonitoreo y la primera de posasentamiento, en las tres localidades, debido a la baja captura de individuos y a la dominancia de Trichiurus lepturus y Lagocephalus laevigatus. Estos resultados fueron distintos en todas las otras investigaciones en las tres localidades, debido a la codominancia de Ctenosciaena gracilicirrhus y
Microfossil assemblage characteristics in Core B10 and implication for paleoenvironmental evolution in the southern Yellow Sea
Zhenbo Cheng,Xuefa Shi,Zhihua Chen,Dongsheng Liu,Zhen Li,Xiaohua Ju
Chinese Science Bulletin , 2003, DOI: 10.1007/BF02900940
Abstract: Microfossil assemblage and pollen zone characteristics in Core B10 recorded the history of environmental changes in the southern Yellow Sea since Würm Subinterglaciation. Environmental variations reflected by these glacial and interglacial sediments coincide with general characteristics of paleoenvironmental and sedimentary changes in the Yellow Sea. In the section of 550-520 cm, microfossil foraminifera have low abundance and diversity, and pollens are composed mainly of those of herbaceous vegetation, indicating climate change during Würm Subinterglaciation. In the section of 520-140 cm, the changes from a few microfossils to no microfossils reflect the sedimentary environment variation from coastal to terrestrial facies. Paleoclimate reflected by pollen also underwent the changes from conifer-broadleaf mixed forest to grassland, indicating the climate changes from temperate and cool type to warm and dry one. In the section of 140-0 cm, the general microfossil characteristics are the gradual increase in abundance with most species being neritic species, the major pollen being ligneous pollen and the rapid increase in small Hystrichosphaera content, which indicates that the air temperature increased and the sea level gradually rose.
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