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Migratory Movements (migratory + movement)
Selected AbstractsMigratory movements of pacu, Piaractus mesopotamicus, in the highly impounded Paraná RiverJOURNAL OF APPLIED ICHTHYOLOGY, Issue 6 2007M. C. Makrakis Summary A mark-recapture study was conducted in 1997,2005 to investigate movements of stocked pacu, Piaractus mesopotamicus, in the Paraná River Basin of Brazil, Paraguay, and Argentina. Fish raised in cages within the Itaipu Reservoir and in ponds were tagged externally (n = 2976) and released in the Itaipu Reservoir (53.2%) and bays of its major tributaries (46.8%). In total, 367 fish (12.3%) were recaptured. In all, 91% of the pacu moved away from the release site; upstream movements were more extensive than downstream movements. Pacu traveled upstream a maximum of 422 km (average of 41.3 km) at a maximum rate of 26.4 km day,1 (av. 0.8). Downstream movements were limited in terms of number of individuals and distance moved. Fish released during the wet season moved farther than those released during the dry season, and feeding rather than spawning might have been the compelling reason for movement. Although fish passed downstream through dams, none of the marked fish were detected to have moved upstream through the passage facilities. Pacu showed movement patterns not radically different from those of other neotropical migratory species, but their migratory movements may not be as extensive as those of other large migratory species in the basin. [source] Survival and expansion: migrants in Greek rural regionsPOPULATION, SPACE AND PLACE (PREVIOUSLY:-INT JOURNAL OF POPULATION GEOGRAPHY), Issue 6 2008Charalambos Kasimis Abstract Migratory movements towards southern Europe have increased considerably in the past 20 years. An important aspect of this process is connected to the agricultural sector and rural regions , a development connected to agriculture's particular weight in the economies and societies of all southern European countries. However, their role is not restricted to agriculture. They are also related to non-agricultural economic activities and the overall support of aged populations, especially in marginal or mountainous rural areas. This paper draws on the qualitative and quantitative findings of two research projects carried out in three exemplar rural regions of Greece and over two different periods: 2000,2002 and 2004,2006. The aim of the research was the empirical investigation of the economic and social implications of the settlement and employment of migrant labour in rural Greece. The paper moves from the presentation of the theoretical and methodological framework to the presentation of the main findings for each period of the research. The socioeconomic implications of migrant employment and settlement in the regions studied are revealed in the light of the recent Common Agricultural Policy changes, and the changes following the implementation of ,regularisation programmes'. Additionally, the characteristics of migration trends in these regions are identified and the formation of new migrant social groups, with different prospects of social integration and mobility, is revealed. Copyright © 2008 John Wiley & Sons, Ltd. [source] MtDNA from extinct Tainos and the peopling of the CaribbeanANNALS OF HUMAN GENETICS, Issue 2 2001C. LALUEZA-FOX Tainos and Caribs were the inhabitants of the Caribbean when Columbus reached the Americas; both human groups became extinct soon after contact, decimated by the Spaniards and the diseases they brought. Samples belonging to pre-Columbian Taino Indians from the La Caleta site (Dominican Republic) have been analyzed, in order to ascertain the genetic affinities of these groups in relation to present-day Amerinds, and to reconstruct the genetic and demographic events that took place during the peopling of the Caribbean. Twenty-seven bone samples were extracted and analyzed for mtDNA variation. The four major Amerindian mtDNA lineages were screened through amplification of the specific marker regions and restriction enzymatic digestion, when needed. The HVRI of the control region was amplified with four sets of overlapping primers and sequenced in 19 of the samples. Both restriction enzyme and sequencing results suggest that only two (C and D) of the major mtDNA lineages were present in the sample: 18 individuals (75%) belonged to the C haplogroup, and 6 (25%) to the D haplogroup. Sequences display specific substitutions that are known to correlate with each haplogroup, a fact that helped to reject the possibility of European DNA contamination. A low rate of Taq misincorporations due to template damage was estimated from the cloning and sequencing of different PCR products of one of the samples. High frequencies of C and D haplogroups are more common in South American populations, a fact that points to that sub-continent as the homeland of the Taino ancestors, as previously suggested by linguistic and archaeological evidence. Sequence and haplogroup data show that the Tainos had a substantially reduced mtDNA diversity, which is indicative of an important founder effect during the colonization of the Caribbean Islands, assumed to have been a linear migratory movement from mainland South America following the chain configuration of the Antilles. [source] Relationship between GABAergic interneurons migration and early neocortical network activityDEVELOPMENTAL NEUROBIOLOGY, Issue 2-3 2009Ana D. de Lima Abstract Available evidence converges to suggest that during the early development of the cerebral cortex, the emergence of the spontaneous network activity chronologically overlap with the end of the cell migration period in the developing cortex. We approached the functional regulation of neuronal migration in a culture model of neocortical networks, using time lapses to detect migratory movements, calcium-imaging to assess the activity of migratory neurons, and immunocytochemical methods to identify the migratory cells retrospectively. In cell cultures, early physiological development and cell migration are reproduced at a local network level, thus allowing the study of the interrelationships between cell migration and network development independent of the topographical complexity. Neurons migrate at least until 12 days in vitro and GABAergic neurons migrate faster compared with non-GABAergic neurons. A decline of migratory activity was coincident with the development of spontaneous synchronous network activity. Migrating interneurons did not participate in synchronous network activity, but interneurons that ended cell migration during observation time frequently engaged in synchronous activity within less than an hour. Application of GABAA and ionotropic glutamate receptor antagonists significantly increased the number of migrating GABAergic neurons without changing the dynamics of the migratory movements. Thus, neurotransmitters released by early network activity might favor the termination of neuronal migration. These results reinforce the idea that network activity plays an important role in the development of late-born GABAergic cells. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] Importance of the Straits of Florida spawning ground to Atlantic sailfish (Istiophorus platypterus) and blue marlin (Makaira nigricans)FISHERIES OCEANOGRAPHY, Issue 6 2009DAVID E. RICHARDSON Abstract Much of the uncertainty in managing highly migratory pelagic species results from the scarcity of fisheries-independent data relevant to determining long-term trends in abundance, migratory movements, and the relative importance of different spawning grounds. To address these issues, we used an ichthyoplankton-based method to quantify the overall level of spawning of sailfish (Istiophorus platypterus) and blue marlin (Makaira nigricans) in the Straits of Florida (SF). We estimated that during the 2 years (2003,2004) of the study, 4.60 × 1011 sailfish eggs and 4.49 × 1011 blue marlin eggs were produced on an annual basis in this region. These egg production values, when combined with estimates of annual fecundity for each species and the most recent stock assessment estimate of total biomass, indicate that about 2.1% of Western Atlantic sailfish spawning and 1.6% of Atlantic-wide blue marlin spawning occurs in the SF. Additionally, pop-up satellite tags deployed on sailfish at the start of the spawning season revealed their short residency times in the SF, suggesting that a large (,13%) transient portion of the sailfish population is responsible for the SF egg production. Overall, this study provides a critically needed fisheries-independent method of quantifying spatial and temporal trends in the abundance of highly migratory species. The application of this methodology in the SF indicated that above-average levels of sailfish and blue marlin spawning occur in this area and, possibly more importantly, that the SF is a migratory bottleneck for these species. [source] Illegality of International Population Movements in PolandINTERNATIONAL MIGRATION, Issue 3 2000Marek Okólski Until the beginning of the 1990s Poland did not receive foreign migrants. Thereafter, the situation changed dramatically. A large part of the inflow proved to be illegal migrants, many of whom were in transit to Western Europe. Although these movements gradually declined in the second half of the decade, some became increasingly identified with relatively sophisticated smuggling of people. Foreigners smuggled from the South to the West, together with the international criminal networks assisting them, became typical of the migratory movements of people in Central and Eastern Europe during the 1990s. This article seeks to describe illegal migration from the perspective of Poland, a country often perceived as a major transit area in the smuggling of persons to Western Europe. The conclusions draw on the findings of several surveys recently carried out in Poland. Basic concepts related to illegal migration are defined and juxtaposed, and various myths and stereotypes concerning it that most often stem from the paucity of empirical evidence are examined. Finally, the trends observed in Poland are interpreted within the larger context of contemporary European migration. [source] Golbalisation, Regional Integration, International MigrationINTERNATIONAL SOCIAL SCIENCE JOURNAL, Issue 165 2000Georges Photios Tapinos After having recalled the two-way links between international migration and development and having placed migratory movements in the con-textof globalisation, the author examines the new situation created by the strengthening of immigration control policies and the relevance of the alternative strategy which considers free trade as a substitute for migration. He examines to what extent the effects of economic liberalisation are likely to modify the decision to emigrate. In conclusion, he outlines various impli-cations for migration policies. [source] Migratory movements of pacu, Piaractus mesopotamicus, in the highly impounded Paraná RiverJOURNAL OF APPLIED ICHTHYOLOGY, Issue 6 2007M. C. Makrakis Summary A mark-recapture study was conducted in 1997,2005 to investigate movements of stocked pacu, Piaractus mesopotamicus, in the Paraná River Basin of Brazil, Paraguay, and Argentina. Fish raised in cages within the Itaipu Reservoir and in ponds were tagged externally (n = 2976) and released in the Itaipu Reservoir (53.2%) and bays of its major tributaries (46.8%). In total, 367 fish (12.3%) were recaptured. In all, 91% of the pacu moved away from the release site; upstream movements were more extensive than downstream movements. Pacu traveled upstream a maximum of 422 km (average of 41.3 km) at a maximum rate of 26.4 km day,1 (av. 0.8). Downstream movements were limited in terms of number of individuals and distance moved. Fish released during the wet season moved farther than those released during the dry season, and feeding rather than spawning might have been the compelling reason for movement. Although fish passed downstream through dams, none of the marked fish were detected to have moved upstream through the passage facilities. Pacu showed movement patterns not radically different from those of other neotropical migratory species, but their migratory movements may not be as extensive as those of other large migratory species in the basin. [source] Seasonal occurrence and local movements of the grey-headed (brown-necked) parrot Poicephalus fuscicollis suahelicus in southern AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2003Craig T. Symes Abstract Seasonal movements of grey-headed (brown-necked) parrots were recorded in parts of its range and are likely a response to breeding and availability of specific food sources. Breeding occurred in the northern Kruger National Park and lowveld near the Mutale,Luvhuvhu river confluence from April to August. Aggregations and movements of birds occurred during the post-breeding season (August,December) in response to seasonally abundant food sources. In north-eastern South Africa, grey-headed parrots occurred at Levubu, following the breeding season and their arrival in the area was correlated with the availability of unripe Mabola Plum, Parinari curatellifolia fruit. Similar regional movements occurred in Zimbabwe, the Caprivi of northern Namibia and Zambia. During these movements, flocks of up to 50 individuals were observed, whilst during breeding months singletons and pairs were more frequently seen. This increased abundance in time and space suggests that seasonal migratory movements occur. Résumé Des déplacements saisonniers de perroquets Poicephalus robustus ont été relevés dans des parties de leur aire de répartition, et ils sont vraisemblablement une réponse aux besoins de la reproduction et à la disponibilité des sources de leur nourriture spécifique. La reproduction avait lieu d'avril à août dans le nord du Parc National Kruger et dans le lowveld près du confluent des rivières Mutale et Luvhuvhu. Des rassemblements et des déplacements d'oiseaux avaient lieu dans la saison qui suivait celle de la reproduction (août , décembre) en réponse à l'abondance saisonnière des sources de nourriture. Au nord-est de l'Afrique du Sud, ces perroquets se rencontraient à Levubu, après la saison de reproduction, et leur arrivée coïncidait à la disponibilité des prunes Mabola (Parinari curatellifolia) avant leur maturité. On constatait des déplacements régionaux saisonniers semblables au Zimbabwe, dans le Capríví au nord de la Namibie et en Zambie. Au cours de ces déplacements, on a observé des bandes qui peuvent compter jusqu'à 50 individus, alors que pendant les mois de reproduction, on voyait plus souvent des solitaires ou des couples. Cette abondance accrue à certains moments et à certains endroits suggère qu'il existe des migrations saisonnières. [source] The European Commission on Factors Influencing Labor MigrationPOPULATION AND DEVELOPMENT REVIEW, Issue 2 2001Article first published online: 27 JAN 200 A controversial issue in discussions on enlargement of the European Union beyond its existing membership of 15 countries is the migration flows that admission of new members could generate. Given major differences in income and wage levels between the EU states and the candidates for membership, casual theorizing suggests that the potential for massive international migration is very high. The fact that such migration has thus far been of modest size by most plausible criteria is attributed to the restrictive policies of the potential destination countries, policies that reflect national interests, in particular protection of labor markets, as perceived by voting majorities. With accession to membership in the EU this factor is removed: a cardinal principle of the Union, established by treaty, is the free movement of persons, including persons seeking gainful employment. The factors governing migratory movements between member states then come to resemble those that shape internal migration. This should facilitate analysis and forecasting. A clear sorting-out of the relevant forces affecting such "internal" migration remains of course an essential precondition for success in that task. An "Information note," entitled The Free Movement of Workers in the Context of Enlargement, issued by the European Commission, the EU's Executive Body, on 6 March 2001, presents extensive discussion of relevant information, opinion, and policy options concerning its topic. (The document is available at «http://europa.eu.int/comm/enlarge-ment/docs/pdf/migration_enl.pdf».) An Annex to the document. Factors Influencing Labour Movement, is a lucid enumeration of the factors migration theory considers operative in determining the migration of workers and, by extension, of people at large, that is likely to ensue upon EU enlargement. This annex is reproduced below. As is evident from the catalog of factors and their likely complex interactions, making quantitative forecasts of future migration flows, envisaged primarily as originating from countries to be newly admitted to the EU and destined for the countries of the current EU15, is exceedingly difficult. This is reflected in disparities among the existing studies that have made such forecasts. Yet there appears to be a fair degree of agreement that major increases in migration are unlikely, suggesting that the overall effect on the EU15 labor market should be limited. Typical forecasts (detailed in the Information note cited above) anticipate that in the initial year after admission, taken to be 2003, total migration from the eight prime candidate countries (the Czech Republic, Hungary, Poland, Slovakia, Slovenia, Estonia, Latvia, and Lithuania: the "CC8") might amount to around 200,000 persons, roughly one-third of which would be labor migration. According to these forecasts, the annual flow will gradually diminish in subsequent years. After 10 to 15 years the stock of CC8 migrants in the EU15 might be on the order of 1.8 to 2.7 million. The longer-run migration potential from the candidate countries would be on the order of 1 percent of the present EU population, currently some 375 million. (The combined current population of the CC8 is 74 million.) Such predictions are in line with the relatively minor migratory movements that followed earlier admissions to the EU of countries with then markedly lower per capita incomes, such as Spain and Portugal. The geographic impact of migration ensuing from enlargement would, however, be highly uneven, with Germany and Austria absorbing a disproportionately large share. Accordingly, and reflecting a prevailing expectation in these two countries that enlargement would have some short-run disruptive effects on labor markets, some of the policy options discussed envisage a period of transition following enlargement,perhaps five to seven years,during which migration would remain subject to agreed-upon restrictions. [source] Prehistorical East,West admixture of maternal lineages in a 2,500-year-old population in XinjiangAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010Fan Zhang Abstract As an area of contact between Asia and Europe, Central Asia witnessed a scenario of complex cultural developments, extensive migratory movements, and biological admixture between West and East Eurasians. However, the detanglement of this complexity of diversity requires an understanding of prehistoric contacts of the people from the West and the East on the Eurasia continent. We demonstrated the presence of genetic admixture of West and East in a population of 35 inhabitants excavated in Gavaerk in southern Xinjiang and dated 2,800,2,100 years before present by analyzing their mitochondrial DNA variations. This result indicates that the initial contact of the East and the West Eurasians occurred further east than Central Asia as early as 2,500 years ago. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. 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