Frequent Migrations Research Articles

Assemblage structure and trophic ecology of deep-sea demersal cephalopods in the Balearic basin (NW Mediterranean)

Despite the important ecological role of cephalopods in energy and material flow in marine ecosystems, they are poorly understood, particularly those inhabiting deep-sea bottoms below 800 m. To define cephalopod species assemblages from the upper to the lower slope, we conducted 13 oceanographic and trawl surveys in the Balearic basin (NW Mediterranean) in 1985–92 and 2007–10 at depths between 450 and 2200 m. Multivariate analysis suggests the existence of three assemblages on the upper (450–600 m), middle (650–1500 m) and lower (1600–2200 m) slopes. Although seasonal changes in species abundance and composition were evident, no significant variations in the assemblage structure were observed between the two time periods. Two main trophic pathways involving deep-sea cephalopods were apparent: species mainly linked to benthic resources and species mostly connected to the pelagic food web through active swimming and frequent vertical migrations. Accordingly, two environmental variables best explained the observed patterns: net primary production and river discharge. Phytoplankton availability controls the increase of zooplankton that influences the distribution and abundance of pelagic cephalopods. River discharge affects, in some instances with delays, transfer of organic matter to the benthic trophic pathway and thus to bottom-dwelling cephalopods.

다중 멀티미디어 스트리밍을 위한 멀티코어 시스템 기반의 실시간 스케줄링 기법

Recently, multi-core processors have been drawing significant interest from the embedded systems research and industry communities due mainly to their potential for achieving high performance and fault-tolerance at low cost in such products as automobiles and cell phones. To process multimedia data, a scheduling algorithm is required to meet timing constraints of periodic tasks in the system. Though Pfair scheduling algorithm can meet all the timing constraints while achieving 100% utilization on multi-core based system theoretically, however, the algorithm incurs high scheduling overheads including frequent core migrations and system-wide synchronizations. To mitigate the problems, we propose a real-time scheduling algorithm for multi-core based system so that system-wide scheduling is performed only when it is absolutely necessary. Otherwise the proposed algorithm performs scheduling within each core independently. The experimental results by extensive simulations show that the proposed algorithm dramatically reduces the scheduling overheads up to as negligible one when the utilization is under 80%.

Seasonal residency and movement patterns of two co‐occurring catadromous percichthyids within a south‐eastern Australian river

Abstract – Understanding movement patterns and habitat utilisation is critical for the management of diadromous fishes. An acoustic telemetry array was used to monitor 33 estuary perch, Macquaria colonorum and 39 Australian bass, Macquaria novemaculeata in the freshwater and estuarine reaches on the Shoalhaven River, south‐east Australia. On average, tagged M. novemaculeata were detected for a considerably shorter period than M. colonorum, and evidence suggested that fishing pressure may have impacted on their survival. Macquaria colonorum displayed significant shifts in seasonal and size‐related habitat use, with fish predominantly residing in deep (>5 m) areas within the middle (mesohaline) reaches of the estuary during the austral spring to autumn months. In winter, M. colonorum individuals made frequent downstream migrations, often to localised areas, within the lower estuary (LE). In contrast, M. novemaculeata were distributed in shallow (<2 m) habitats throughout the year, within the upper (oligohaline) estuarine reaches of the river, as well as in fresh water. Like M. colonorum, M. novemaculeata made extensive downstream and upstream movements, often coincident with reproductive behaviour, water temperature and increased freshwater inflows. It is postulated that the high site fidelity and repetitive homing displayed by both species is influenced by ontogenetic behaviour and prey availability. Furthermore, the extent of instream distribution by both species, and the lack of observed annual spawning migrations by some M. novemaculeata individuals, indicates the once considered ‘catadromous’ life cycle of these fishes may not be obligatory. A management approach is recommended to ensure that both these species are not over‐exploited within a portion of their instream range, thus maintaining their full reproductive potential.

Climate-induced fluvial dynamics in tropical Africa around the last glacial maximum?

The alluvia of the Ntem, Nyong and Sanaga fluvial systems in southern Cameroon recorded repeated fluvial activity fluctuations during the Late Pleistocene, including the last glacial maximum (LGM), the beginning of the African Humid Period and the northern hemispheric Bølling-Allerød. We applied a multi-proxy approach on alluvial stratigraphies dated between 22.4 and 13.0 cal ka BP, including remote sensing, sedimentological and morphogenetic methods, phytoliths, sponge spicules, 14C and δ 13C data. A distinct NE–SW gradient of landscape and fluvial dynamics around the LGM can be drawn, with evidence for the persistence of extended fluvial rainforest refuges only in the Ntem catchment. The Sanaga and Nyong catchment areas were characterized by frequent channel migrations, floodplain reorganization and unstable vegetation subject to fire, including grasslands, woodlands, and gallery forests with bamboo thickets. In spite of increasing rainfall after 16.4 cal ka BP, persisting landscape instability played the major role for fluvial system dynamics, floodplain transformations and vegetation development until 13.0 cal ka BP, before a general landscape stabilization and rainforest expansion set in at the beginning of the Holocene.

Competition and Cooperation in One-Dimensional Stepping-Stone Models

Mutualism is a major force driving evolution and sustaining ecosystems. Although the importance of spatial degrees of freedom and number fluctuations is well known, their effects on mutualism are not fully understood. With range expansions of microbes in mind, we show that, even when mutualism confers a selective advantage, it persists only in populations with high density and frequent migrations. When these parameters are reduced, mutualism is generically lost via a directed percolation (DP) process, with a phase diagram strongly influenced by an exceptional symmetric DP (DP2) transition.

멸종위기종 붉은점모시나비(Parnassius bremeri )의 메타개체군 구조와 이주

메타개체군의 구조와 이주에 관한 이해는 종 보존을 위해서 필요하다. 본 연구는 붉은점모시나비 서식지에서 MRR 방법으로 나비의 이주패턴을 분석하고 패치연결성을 추정하였다. 그 결과 194(수컷: 137, 암컷: 57)개체가 포획 되었으며 이중 93 (수컷: 73, 암컷: 20)개체가 재포획되었다. 이주 분석에서 이입율은 23-150%, 이출율은 28-53%으로 나타났다. 패치면적과 이입 이출 개체수와의 회귀분석에서는 상관관계를 보이지 않았으며, 먹이식물 수와 이입 이출 개체수와의 회귀분석에서도 상관관계를 보이지 않았다. 그러나 이입 개체수와 패치간 거리와의 분석에서는 높은 상관관계를 보였다. 따라서 나비의 이주는 패치거리가 가까울수록 빈번하게 일어나고 있으나 패치의 면적이나 먹이식물 량과 관계가 없는 것으로 나타났다. 나비의 이주에서 암컷보다 수컷이 매우 활발한 것으로 나타났다. 패치의 위치에 따른 이주 패턴의 분석 결과 패치 네트워크상에서 중앙에 위치한 패치가 양쪽 끝에 위치한 개체군을 이어주는 역할을 하고 있으며 근접한 거리에 있는 패치들간 이주가 멀리 떨어진 패치에 비해 빈번한 이주가 일어나는 것을 보여주었다. 따라서 붉은점모시나비의 이주에 있어서 근거리에 위치한 패치들간 교류가 활발히 일어나고 있으며 패치와 패치를 이어주는 징검다리 역할을 하는 패치가 존재할 경우 교류가 더 활성화된다는 것을 제시하고 있다. Understanding the metapopulation structure and movement of a species are required for conserving the species. In this paper, migration patterns and connectivity of patches of a threatened butterfly, Parnassius bremeri Bremer, were postulated using the mark-release-recapture (MRR) technique in a habitat located in the mid-southern region of the Korean peninsula. A total of 194 individuals were captured (137 males and 57 females) and, of them, 93 individuals (73 males and 20 females) were recaptured during the MRR experiment. The migration analysis showed 23-150% immigration and 28-53% emigration. There were high correlations between the migrating individuals and the distance between patches, but there was no correlation between migrating individuals and patch size or between migrating individuals and the number of host plants. Consequently, the migration of butterflies occurred frequently between closer patches, while patch size and quantity of the food plant had minor effects on migration behavior. Additionally, males migrated more frequently than females. Analysis of the migration patterns of P. bremeri showed that the central patch played an important role on linking patch groups and more frequent migrations were monitored between nearby patches than between the remote patches. This study suggested that active migrations take place between the neighboring multiple patches and these are accelerated if there is a stepping-stone patch between them.

Sticky-ERfair: a task-processor affinity aware proportional fair scheduler

A drawback of current proportional fair schedulers is that they ignore task-to-processor mutual affinities, thereby causing frequent inter-processor task migrations and cache misses. This paper presents the Sticky-ERfair Scheduler, an Early-Release Fair (ERfair) scheduler that attempts to minimize task migrations and preemptions. Given any processor V i , Sticky-ERfair allocates to it the most recently executed ready task that previously executed on V i (thus restricting migrations and preemptions) in such a way that this allocation does not cause any ERfairness violations in the system at any time during the schedule length. Experimental results reveal that Sticky-ERfair can achieve upto over 40 times reduction both in the number of migrations and preemptions suffered with respect to Basic-ERfair (for a set of 25 to 100 tasks running on 2 to 10 processors) while simultaneously guaranteeing ERfairness at each time slot.

Chagas disease: serological and electrocardiographic studies in Wichi and Creole communities of Misión Nueva Pompeya, Chaco, Argentina

Chagas disease, which is caused by Trypanosoma cruzi, affects nearly 16 million people in Latin America and causes 75-90 million people to be at risk of infection. The disease is urbanizing and globalizing due to frequent migrations. There are regions of high prevalence of infection, including the north-eastern provinces of Argentina and the entire phytogeographic region known as the Gran Chaco. In the province of Chaco, Argentina, there are places inhabited by native populations such as the Wichi and Toba communities, among others. Many Creole populations resulting from miscegenation with European colonists and immigrants coexist within these communities. It has been widely accepted that in the chronic phase of the disease, between 25-30% of individuals develop some form of cardiac disease, with the right bundle-branch block being the most typical condition described so far. The aim of this work was to study the prevalence of Chagas infection and its electrocardiographic profile in the Wichi and Creole populations of Misión Nueva Pompeya, in the area known as Monte Impenetrable in Chaco, to determine the prevalence and the pattern of heart diseases produced by Chagas disease in this region.

Partition oriented frame based fair scheduler

Proportionate fair schedulers provide an effective methodology for scheduling recurrent real-time tasks on multiprocessors. However, a drawback in these schedulers is that they ignore a task’s affinity towards the processor where it was executed last, causing frequent inter-processor task migrations which ultimately results in increased execution times. This paper presents Partition Oriented Frame Based Fair Scheduler (POFBFS), an efficient proportional fair scheduler for periodic firm and soft real-time tasks that ensures a bounded number of task migrations. Experimental results reveal that POFBFS can achieve 3 to 100 times reduction in the number of migrations suffered with respect to the General-ERfair algorithm (for a set of 25 to 100 tasks running on 2 to 8 processors) while simultaneously maintaining high fairness accuracy.

Multi-scale patterns of habitat use in a highly mobile reef fish, the white trevally Pseudocaranx dentex, and their implications for marine reserve design

The fisheries benefits of marine reserves are hard to achieve for highly vagile fish species. An alternative is to protect essential habitats, such as spawning grounds, especially if these are stable over time. We studied the movements and habitat use patterns of white trevally Pseudo- caranx dentex (Carangidae), a commercially important species, to assist in the design of marine reserves. Diel, seasonal and inter-annual movements of trevally were studied using active acoustic tracking, passive acoustic monitoring and standard tag-release in the Faial Channel, Azores Islands. White trevally were captured at inshore and offshore reefs. Inshore trevally moved daily alongshore, using large activity spaces, while the short-term movements of offshore trevally were restricted to the reef summits. During the summer spawning season, both groups displayed frequent migrations of up to several kilometres, but inshore fish remained inshore, whereas offshore reef fish expanded their range to include visits to inshore sites. This behaviour eventually resulted in low long-term residence within the study area, especially that of inshore fish. During the spawning season, one inshore site was visited by most of the fish. However, instead of gathering in large aggregations at a single location, it appears that the trevally adopted a multiple-site visiting behaviour, which may increase mating opportunities through mixing between inshore and offshore fish that are otherwise segre- gated for most of the year. Protection of spawning biomass and sites for this species seems potentially feasible, but this would require protecting a suite of sites per island. Furthermore, because fish would not be fully protected under this scenario, we argue that such spatial management measures need to be accompanied by conventional fishing-effort control measures applied to all local populations.

The maternal aborigine colonization of La Palma (Canary Islands)

Teeth from 38 aboriginal remains of La Palma (Canary Islands) were analyzed for external and endogenous mitochondrial DNA control region sequences and for diagnostic coding positions. Informative sequences were obtained from 30 individuals (78.9%). The majority of lineages (93%) were from West Eurasian origin, being the rest (7%) from sub-Saharan African ascription. The bulk of the aboriginal haplotypes had exact matches in North Africa (70%). However, the indigenous Canarian sub-type U6b1, also detected in La Palma, has not yet been found in North Africa, the cradle of the U6 expansion. The most abundant H1 clade in La Palma, defined by transition 16260, is also very rare in North Africa. This means that the exact region from which the ancestors of the Canarian aborigines came has not yet been sampled or that they have been replaced by later human migrations. The high gene diversity found in La Palma (95.2+/-2.3), which is one of the farthest islands from the African continent, is of the same level than the previously found in the central island of Tenerife (92.4+/-2.8). This is against the supposition that the islands were colonized from the continent by island hopping and posterior isolation. On the other hand, the great similarity found between the aboriginal populations of La Palma and Tenerife is against the idea of an island-by-island independent maritime colonization without secondary contacts. Our data better fit to an island model with frequent migrations between islands.

THE CONSUMPTION OF FRUIT FOR THE YEAR 2007

The consumption of agricultural food products is continuous biological and social process which is of utmost importance for each individual as well as for an entire community. Today, in Serbia and Montenegro, we can witness irregularities regarding proper nourishment of population which affects the health and well-being of entire Nation. Frequent migrations, low wages and increased cost of living, have contributed to continuous negative trends regarding nourishment. The basic goal of this paper is to survey fruit consumption in Serbia and Montenegro per capita, for the period of 1992-2002, in total. Also, this paper will signify state and trends of fruit consumption in Serbia and Montenegro and position of our country in Europe, based on the attained parameters. Particular instances will be compared with previous periods, so as to review the changes in consumption. Based on forecasting value of trends, consumption of fruit in Serbia and Montenegro for the year 2007 will be predicted. This paper will provide theoretical and practical contribution for those responsible to carry out adequate actions to improve fruit production and consumption in Serbia and Montenegro.

A model for the active origin and development of source-bordering dunefields on a semiarid fluvial plain: A case study from the Xiliaohe Plain, Northeast China

Source-bordering dunefields have been reported in some drylands of the planet, but scarcely in China where there are extensive drylands. This article reports them in China for the first time, and presents a model for their active origin and development on a semiarid fluvial plain by means of satellite image analyses and field investigations. Local- and regional-scale examples are chosen to analyze the spatial patterns of dunefields, as well as the relationships with the fluvial systems in the central part of Naiman Banner where the Jiaolai River runs, and the lower Laoha River, and the middle and lower Ulijimulun River (principal tributaries of the Xiliaohe River). The active origin and development of source-bordering dunefields can be divided into four stages in terms of the spatial patterns of dunefields and channel dynamics: Stage I — individual dunes on the downwind margins of river valleys where running water constantly erodes the steep slopes of valley and where the downwind slopes orient to local dominant winds; Stage II — individual local-scale dunefields formed by deflation of the steep valley slopes and extending antecedent dunes downwind, together with the downstream displacement of meanders; Stage III — individual large-scale dunefield belts along the downwind margins of river valleys formed through frequent lateral migrations of channel; Stage IV — regional-scale dunefields formed mainly by river diversions due to climatic changes or tectonic movements. On the one hand, it is the running water's lateral migration, especially meandering, that prepares suitable places for aeolian systems in terms of both wind flow fields and sand sources, and subsequently it can further cause separate local-scale source-bordering dunefields to link together as a regional-scale dunefield belt given sufficient time. On the other hand, diversions of the river are bound to occur following changing hydrologic regimes resulting from tectonic movements or significant climate change (at regional and millennium scales). As a result, when some dunefield belts as well as the adjacent channels are abandoned, new channels work elsewhere in the same way to actively form new source-bordering dunefields and even dunefield belts at a regional scale.

Permanentemente temporário: dekasseguis brasileiros no Japão

Este texto apresenta os resultados de parte de um projeto empreendido pela ABD (Associação Brasileira de Dekasseguis) sobre os dekasseguis, particularmente a partir dos dados do questionário aplicado a esses migrantes brasileiros no Japão, em janeiro de 2004. Uma grande barreira à adaptação dos dekasseguis no Japão está relacionada à língua e aos costumes. A maior parte, embora apresente um fenótipo de nativo japonês e possua ancestrais japoneses razoavelmente próximos, não se comporta mais como japonês. Esta aparente contradição entre o ser e o parecer gera conflitos de adaptação dos migrantes e de aceitação pelos nativos. Este conflito de identidade já existia no Brasil, mas a ida ao Japão só reforça o sentimento de não pertinência a este país e, conseqüentemente, reforça a identidade brasileira, expressa pela grande proporção de indivíduos que declaram "saudades do Brasil" como o problema que enfrenta no Japão. A pesquisa apontou que a motivação da ida ao Japão está ligada principalmente a questões econômicas, o que explica também a maior proporção de homens que viajam sozinhos e os reiterados retornos no caso de insucesso no Brasil, principalmente para o pessoal de mais baixa escolaridade. A situação dos dekasseguis com reiteradas idas e vindas no eixo Brasil-Japão, migrações internas freqüentes, bem como mudanças de emprego e passagens por períodos de desemprego no Japão (ainda que possivelmente curtos), tipificam o movimento dekassegui.

Lexical and semantic influences on item and order memory in immediate serial recognition: evidence from a novel task.

Previous studies have reported that, in contrast to the effect on immediate serial recall, lexical/semantic factors have little effect on immediate serial recognition. This has been taken as evidence that linguistic knowledge contributes to verbal short-term memory in a redintegrative process at recall. Contrary to this view, we found that lexicality, frequency, and imageability all influenced matching span. The standard matching span task, requiring changes in item order to be detected, was less susceptible to lexical/semantic factors than was a novel task involving the detection of phoneme order and hence item identity changes. Therefore, in both immediate recognition and immediate serial recall, lexical/semantic knowledge makes a greater contribution to item identity than to item order memory. Task sensitivity, and not the absence of overt recall, may have underpinned previous failures to show effects of these variables in immediate recognition. We also compared matching span for pure and unpredictable mixed lists of words and nonwords. Lexicality had a larger impact on immediate recognition for pure than for mixed lists, in line with findings for immediate serial recall. List composition affected the detection of phoneme but not item order changes in matching span; similarly, in recall, mixed lists produce more frequent word phoneme migrations but not migrations of entire items. These results point to strong similarities between immediate serial recall and recognition. Lexical/semantic knowledge may contribute to phonological stability in both tasks.

Effects of fluvial geomorphology on riparian tree species in Rekifune River, northern Japan

Classification of riverbed geomorphic surfaces based on flooding frequency was conducted and the relationship between their distribution and river morphology was analyzed, to provide an understanding of the structure and species composition of riparian forests dominated by Chosenia arbutifolia. The channel floors of two contrasting river morphologies (bar-braided and incised meandering channels), were divided into five geomorphic surfaces (gravel bar, lower and upper floodplains, secondary channel, and terrace) based on the water level of a 2-yr and a 20-yr recurrence interval. The environmental variables of the same geomorphic surfaces showed similar trends regardless of braided and meandering channel morphology, but differed significantly among the five geomorphic surfaces, which influenced the dominance of tree species. The geomorphic surface map based on recurrence interval of flood and physiognomical vegetation map based on aerial photos appeared almost identical. Geomorphic surface distribution, determined by river channel dynamics and the sediment transport processes occurring at a larger scale and a longer time frame, played an important role in shaping the structure and composition of the riparian forests. C. arbutifolia dominated gravel bar, and the upper and lower floodplains, because these geomorphic surfaces were characterized by gravelly soils which have lower soil moisture availability than soils of other geomorphic surfaces. Thus, an extensive distribution of C. arbutifolia in the braided channel section can be attributed to the frequent lateral migrations of river channels, which resulted in a high ratio of gravel bars, and lower and upper floodplains. In order to preserve indigenous plant communities in riparian zone, dynamic nature and processes of braided rivers should be maintained.

Not a one-way trip: historical distribution data for Australian plague locusts support frequent seasonal exchange migrations

An analysis of the development of infestations of the Australian plague locust (Chortoicetes terminifera) (Walker) (Orthoptera: Acrididae) from 1977–1995 in eastern Australia is presented which traces the sequence of generations and redistribution of gregarious populations through migration. Migration in this species has previously been viewed as a one-way trip, locusts reaching southern regions of the species range were thought to have no reliable means of return to the areas of summer population increase in western Queensland. However, a study of outbreaks over recent years, using new technologies for simulating and observing migratory events, suggested a pattern of exchange migrations, with northward movements in November and December.In this paper we provide further evidence of migrations to western Queensland from populations in the southern or eastern parts of the species range. Several northward or westward migrations from New South Wales, South Australia or eastern Queensland are identified from historic distribution data and supported by meteorological records. These migrations were significant in that they allowed the rapid re-establishment of gregarious populations in arid western Queensland after summer rains. The frequency of late-spring northward migrations is comparable to that of the better-known southward migrations in autumn. The evidence for previous conclusions about the source of historical plagues and the importance of spring breeding in arid southwest Queensland are re-examined in the light of these findings.

Local endemism within the Western Ghats-sri Lanka biodiversity hotspot.

The apparent biotic affinities between the mainland and the island in the Western Ghats-Sri Lanka biodiversity hotspot have been interpreted as the result of frequent migrations during recent periods of low sea level. We show, using molecular phylogenies of two invertebrate and four vertebrate groups, that biotic interchange between these areas has been much more limited than hitherto assumed. Despite several extended periods of land connection during the past 500,000 years, Sri Lanka has maintained a fauna that is largely distinct from that of the Indian mainland. Future conservation programs for the subcontinent should take into account such patterns of local endemism at the finest scale at which they may occur.

Swimming speeds and buoyancy compensation of migrating adult chum salmon Oncorhynchus keta revealed by speed/depth/acceleration data logger.

Although the homing migration of Pacific salmon is well documented, the swimming behaviour of the returning salmon has been poorly described, principally as a result of the difficulties encountered in monitoring salmon behaviour in the sea. The present study describes the use of a recently developed electronic data logger to obtain simultaneous recordings of the swimming speed, depth, fin-beating activity and body angle of free-ranging chum salmon Oncorhynchus keta during their homing migration in coastal waters. Chum salmon migrated horizontally at speeds of 1.5-3.0 km h(-1). The gross horizontal distance salmon moved during total recording periods were 1.24- to 19.0-fold greater than the net distance from the release site to the retrieval points. It is suggested that homing salmon did not drift passively but swam actively to the spawning grounds. Salmon preferred the surface water, but also made frequent vertical migrations. The travelled depth of each salmon ranged from 0.36 to 0.64 km per hour. Salmon descended at faster rates and steeper angles than they ascended. Both tailbeat frequency and tail thrust were higher during the ascent than the descent phase. These results suggest that chum salmon spent more energy during the ascent than the descent phase. Profiles of descent rate assumed an arched shape with respect to a change in hydrostatic pressure, while ascent rate increased with decreasing depth. High tailbeat frequencies were found during the course of ascent, which suggests that the salmon did not regulate the volume of air in the swim bladder during short-term vertical migrations.

ACM SIGCOMM computer communication review

At some point in the future, how far out we do not exactly know, wireless access to the Internet will outstrip all other forms of access bringing the freedom of mobility to the way we access the we...