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Migration Barriers (migration + barrier)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

Habitat suitability analysis for lacustrine brown trout (Salmo trutta) in Lake Walchensee, Germany: implications for the conservation of an endangered flagship species

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2010
Marco Denic
Abstract 1.The lacustrine brown trout (Salmo trutta) is endangered and of high conservation importance. In the only spawning habitat of the population in the Bavarian Lake Walchensee, the River Obernach, a substantial decrease in spawning runs has been reported. In this study, the present ecological state of the spawning stream was analysed with the objective of identifying life-stage specific limitations to successful recruitment attributable to deficiencies in (i) spawning migration, (ii) spawning habitat quality, and (iii) habitat quality for juveniles. 2.Structural stream analysis showed that discharge and several migration barriers , particularly near the river outlet into the lake , prevent successful spawning migrations at normal water levels. Migration barriers are probably the main limiting factor for reproduction of lacustrine brown trout, whereas structural variability of the Obernach meets the habitat requirements of both spawners and juveniles. 3.Spawning site quality was suitable for trout, as indicated by stream substratum texture and high exchange rates between free-flowing water and the interstitial zone in physico-chemical parameters (redox potential, dissolved oxygen, pH, temperature and conductivity). 4.Analyses of fish community structure revealed dominance of lithophilic species, in particular of riverine brown trout (Salmo trutta). Its density and intact demographic population structure suggest that spawning and juvenile habitat quality for salmonids is not limiting. Recapture of stocked lacustrine trout juveniles also indicates habitat suitability for the juvenile stage. 5.In conclusion, the results show that the methodology used in this study is suitable for the identification of life-stage specific habitat deficiencies in lacustrine brown trout and other fish species. Availability of habitat data throughout the species' distribution range is a first crucial step for the development of an effective recovery plan. Copyright © 2009 John Wiley & Sons, Ltd. [source]

The invasive behaviour of prostatic cancer cells is suppressed by inhibitors of tyrosine kinase,

APMIS, Issue 1 2006
HAAKON SKOGSETH
Proteolytic enzymes, and especially urokinase plasminogen activator (uPA), play an important role in tumour invasion and metastasis. Previously we demonstrated that the production of urokinase plasminogen activator (uPA) was decreased by several tyrosine kinase inhibitors (TKI) in two prostatic carcinoma cell lines. The effect of the two TKI genistein and tyrphostin AG-1478 was investigated in the prostate carcinoma cell lines PC-3 and DU-145. A reconstituted basal lamina (Matrigel) was used as a migration barrier. The production of matrix metalloproteinases (MMP) was also measured. Roles of plasminogen and uPA were examined. Cell invasion was increased by plasminogen, but this enhanced cell migration was counteracted by TKI treatment. The increased cell invasion induced by plasminogen was decreased by at least 60% in both cell lines when ,-2 anti-plasmin was added to the assay. Cells in the absence of plasminogen were not affected by TKI. External uPA failed to regenerate the decreased cell invasion caused by TKI. The production of MMP was inhibited by both TKI. Our results indicate a possible role of TKI as inhibitors of cancer cell invasion by inhibiting uPA and MMP production. [source]

UNCOORDINATED PHYLOGEOGRAPHY OF BORRELIA BURGDORFERI AND ITS TICK VECTOR, IXODES SCAPULARIS

EVOLUTION, Issue 9 2010
Parris T. Humphrey
Vector-borne microbes necessarily co-occur with their hosts and vectors, but the degree to which they share common evolutionary or biogeographic histories remains unexplored. We examine the congruity of the evolutionary and biogeographic histories of the bacterium and vector of the Lyme disease system, the most prevalent vector-borne disease in North America. In the eastern and midwestern US, Ixodes scapularis ticks are the primary vectors of Borrelia burgdorferi, the bacterium that causes Lyme disease. Our phylogeographic and demographic analyses of the 16S mitochondrial rDNA suggest that northern I. scapularis populations originated from very few migrants from the southeastern US that expanded rapidly in the Northeast and subsequently in the Midwest after the recession of the Pleistocene ice sheets. Despite this historical gene flow, current tick migration is restricted even between proximal sites within regions. In contrast, B. burgdorferi suffers no barriers to gene flow within the northeastern and midwestern regions but shows clear interregional migration barriers. Despite the intimate association of B. burgdorferi and I. scapularis, the population structure, evolutionary history, and historical biogeography of the pathogen are all contrary to its arthropod vector. In the case of Lyme disease, movements of infected vertebrate hosts may play a larger role in the contemporary expansion and homogenization of the pathogen than the movement of tick vectors whose populations continue to bear the historical signature of climate-induced range shifts. [source]

Migration of rheophilic fish in the large lowland rivers Meuse and Rhine, the Netherlands

FISHERIES MANAGEMENT & ECOLOGY, Issue 5-6 2008
J. J. DE LEEUW
Abstract, Large-scale migratory patterns of adult rheophilic fish [barbel, Barbus barbus (L.), chub, Leuciscus cephalus (L.), ide, Leuciscus idus (L.), nase, Chondrostoma nasus (L.)] were studied in relation to habitat quality and possible migration barriers in the lower rivers Meuse and Rhine, the Netherlands, using a telemetry system with transponders and detection stations based on inductive coupling. Most fish moved over short distances (<10 km), especially those residing in river stretches with high habitat diversity year-round. About 16% of fish used river stretches over 50 km and two ide moved more than 200 km along free-flowing river stretches. One-third of barbel, chub and nase from a Weir-regulated river stretch moved upstream during the spawning season to spawning habitats. Some fish resided in the areas immediately downstream of weirs and fishways during the spawning season, although it was unclear to what extent these observations reflected habitat choice or barriers to migration. [source]

Upstream migration of Atlantic salmon at a power station on the River Nidelva, Southern Norway

FISHERIES MANAGEMENT & ECOLOGY, Issue 3 2003
E. B. Thorstad
Abstract The upstream migration of 17 radio-tagged adult Atlantic salmon, Salmo salar L., past hydroelectric developments on the River Nidelva, Southern Norway, was examined. Salmon migrated quickly from the site of release in the lower part of the river up to the tunnel outlet of Rygene power station, but were substantially delayed at the outlet. The salmon stayed in the outlet area for 0,71 days (median = 20), and mainly took up a position inside the dark power station tunnel. Water discharge in the tunnel was 57,176 m3 s,1, while residual flow in the river between the outlet and the dam 2.5 km further upstream was 3 m3 s,1. Ten salmon passed the outlet and entered the residual flow stretch, but none passed the dam. Six of the 10 salmon returned to the tunnel outlet. No major migration barriers were identified in the residual flow stretch, suggesting lack of motivation among the salmon to migrate due to either low water discharge compared with the main river, or several minor migration barriers along the river stretch. [source]

Habitat suitability analysis for lacustrine brown trout (Salmo trutta) in Lake Walchensee, Germany: implications for the conservation of an endangered flagship species