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Tributaries
Kinds of Tributaries Selected AbstractsFluoroscopy-Guided Endovenous Foam Sclerotherapy Using a Microcatheter in Varicose Tributaries Followed by Endovenous Laser Treatment of Incompetent Saphenous Veins: Technical Feasibility and Early ResultsDERMATOLOGIC SURGERY, Issue 5 2009SANG WOO PARK MD OBJECTIVES To evaluate the technical feasibility and preliminary results of endovenous foam sclerotherapy using a microcatheter in varicose tributaries followed by endovenous laser treatment (EVLT) of incompetent saphenous veins. MATERIALS AND METHODS From July 2005 to August 2006, 312 patients (M:F=139:173, mean age 45.8) who presented with varicose veins with reflux in the saphenofemoral, saphenopopliteal junction or tributaries were enrolled. Under ultrasound or fluoroscopy guidance, selective microcatheterization and endovenous foam slcerotherapy were first performed in varicose tributaries, followed by EVLT (980 nm) of incompetent saphenous veins. Follow-up at 1-week and 1-, 3-, and 6-month intervals was done. RESULTS Technical success was seen in 410 of 411 limbs (99%). Continued closure of the saphenous veins and the complete sclerosis of varicose tributaries were noted in 332 of 373 limbs (89%) at the 1-month follow-up, all 307 limbs (100%) at the 3-month follow-up, and all 274 limbs (100%) at the 6-month follow-up. No serious complication was noted. CONCLUSION Endovenous foam sclerotherapy using a microcatheter in varicose tributaries followed by EVLT in incompetent saphenous veins is a safe, effective, and technically feasible treatment for varicose veins. It not only reduces additional sclerotherapy and technical failure, but also makes multiple therapeutic sessions unnecessary. [source] Distribution of cytochrome P4501A1,inducing chemicals in sediments of the Delaware River-Bay system, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2002Daniel L. McCoy Abstract The Delaware River-Bays system, USA, was the subject of a study by the National Oceanic and Atmospheric Administration that involved chemical and biological analyses, including the use of the biomarker P450 human reporter gene system (HRGS) to document the occurrence and distribution of cytochrome P450 (CYP) 1A1-inducing compounds. Sediment extracts from 81 locations along the Delaware River, Delaware Bay and immediate coastline were tested by utilizing HRGS as an inexpensive screening test, and were also analyzed for polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls, with selected stations analyzed for dioxins and furans. Benthic community degradation has been observed when benzo[a]pyrene equivalents (BaPEq) exceeded 60 ,g/g. The average levels of BaPEq for the largely industrialized upper, middle, and lower regions of the Delaware River were 107, 62, and 5 ,g/g, respectively, excluding outliers. Tributaries leading into river averaged 21 ,g/g BaPEq, whereas the central Bay and open coast had relatively low values (2.0 and 0.5 ,g/g BaPEq, respectively). The HRGS values were highly correlated with total PAHs measured in the same sediment samples (r2 = 0.81). Overall, contamination levels consistently decreased from the upper and middle river sites as collection locations progressed down through the lower river and bay to the coast. Thus, despite the relatively high contaminant load in the river system, Delaware Bay and the immediate coastline seem to have relatively low levels of contaminants, and, therefore, impacts on the benthic organisms in the bay and coast would not be expected from these findings. [source] Spatial and temporal variations in bank erosion on sand-bed streams in the seasonally wet tropics of northern AustraliaEARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2006M. J. Saynor Abstract Bank erosion rates and processes across a range of spatial scales are poorly understood in most environments, especially in the seasonally wet tropics of northern Australia where sediment yields are among global minima. A total of 177 erosion pins was installed at 45 sites on four sand-bed streams (Tributaries North and Central, East Tributary and Ngarradj) in the Ngarradj catchment in the Alligator Rivers Region. Bank erosion was measured for up to 3·5 years (start of 1998/99 wet season to end of 2001/02 wet season) at three spatial scales, namely a discontinuous gully (0·6 km2) that was initiated by erosion of a grass swale between 1975 and 1981, a small continuous channel (2·5 km2) on an alluvial fan that was formed by incision of a formerly discontinuous channel between 1964 and 1978, and three medium-sized, continuous channels (8·5,43·6 km2) with riparian vegetation. The bank erosion measurements during a period of average to above-average rainfall established that substantial bank erosion occurred during the wet season on the two smaller channels by rapid lateral migration (Tributary Central) and by erosion of gully sidewalls due to a combination of within-gully flows and overland flow plunging over the sidewalls (Tributary North). Minor bank erosion also occurred during the dry season by faunal activity, by desiccation and loss of cohesion of the sandy bank sediments and by dry flow processes. The larger channels with riparian vegetation (East Tributary and Ngarradj) did not generate significant amounts of sediment by bank erosion. Deposition (i.e. negative pin values) was locally significant at all scales. Bank profile form and channel planform exert a strong control on erosion rates during the wet season but not during the dry season. Copyright © 2006 Commonwealth Government of Australia. [source] Conservation Strategies for Endemic Fish Species Threatened by the Three Gorges DamCONSERVATION BIOLOGY, Issue 6 2003YOUNG-SEUK PARK diseño de reserva; especies endémicas; modelo de comunidad; peces; presa Three Gorges Abstract: The largest damming project to date, the Three Gorges Dam has been built along the Yangtze River (China), the most species-rich river in the Palearctic region. Among 162 species of fish inhabiting the main channel of the upper Yangtze, 44 are endemic and are therefore under serious threat of global extinction from the dam. Accordingly, it is urgently necessary to develop strategies to minimize the impacts of the drastic environmental changes associated with the dam. We sought to identify potential reserves for the endemic species among the 17 tributaries in the upper Yangtze, based on presence/absence data for the 44 endemic species. Potential reserves for the endemic species were identified by characterizing the distribution patterns of endemic species with an adaptive learning algorithm called a "self-organizing map" (SOM). Using this method, we also predicted occurrence probabilities of species in potential reserves based on the distribution patterns of communities. Considering both SOM model results and actual knowledge of the biology of the considered species, our results suggested that 24 species may survive in the tributaries, 14 have an uncertain future, and 6 have a high probability of becoming extinct after dam filling. Resumen: El proyecto de represa más grande a la fecha, la Presa Three Gorges fue construida en el Río Yangtze (China), el río con mayor riqueza de especies en la región Paleártica. Entre las 162 especies de peces que habitan el canal principal del alto Yangtze, 44 son endémicas y por tanto están seriamente amenazadas de extinción global por la presa. Consecuentemente, es urgente desarrollar estrategias para minimizar los impactos de los cambios ambientales drásticos asociados con la presa. Tratamos de identificar las reservas potenciales para las especies endémicas entre los 17 afluentes en el alto Yangtze, en base a datos de presencia y ausencia de las 44 especies endémicas. Se identificaron las reservas potenciales para la especies endémicas caracterizando los patrones de distribución de especies endémicas con un algoritmo de aprendizaje adaptivo denominado "mapa auto-organizante" (MAO). Con este método, también predijimos las probabilidades de ocurrencia de especies en reservas potenciales en base a los patrones de distribución de las comunidades. Tomando en cuenta tanto los resultados del modelo MAO como el conocimiento actual de la biología de especies en consideración, nuestros resultados sugieren que 24 especies pueden sobrevivir en los afluentes, 14 tienen un futuro incierto y 6 tienen una alta probabilidad de extinguirse después del llenado de la presa. [source] Fluoroscopy-Guided Endovenous Foam Sclerotherapy Using a Microcatheter in Varicose Tributaries Followed by Endovenous Laser Treatment of Incompetent Saphenous Veins: Technical Feasibility and Early ResultsDERMATOLOGIC SURGERY, Issue 5 2009SANG WOO PARK MD OBJECTIVES To evaluate the technical feasibility and preliminary results of endovenous foam sclerotherapy using a microcatheter in varicose tributaries followed by endovenous laser treatment (EVLT) of incompetent saphenous veins. MATERIALS AND METHODS From July 2005 to August 2006, 312 patients (M:F=139:173, mean age 45.8) who presented with varicose veins with reflux in the saphenofemoral, saphenopopliteal junction or tributaries were enrolled. Under ultrasound or fluoroscopy guidance, selective microcatheterization and endovenous foam slcerotherapy were first performed in varicose tributaries, followed by EVLT (980 nm) of incompetent saphenous veins. Follow-up at 1-week and 1-, 3-, and 6-month intervals was done. RESULTS Technical success was seen in 410 of 411 limbs (99%). Continued closure of the saphenous veins and the complete sclerosis of varicose tributaries were noted in 332 of 373 limbs (89%) at the 1-month follow-up, all 307 limbs (100%) at the 3-month follow-up, and all 274 limbs (100%) at the 6-month follow-up. No serious complication was noted. CONCLUSION Endovenous foam sclerotherapy using a microcatheter in varicose tributaries followed by EVLT in incompetent saphenous veins is a safe, effective, and technically feasible treatment for varicose veins. It not only reduces additional sclerotherapy and technical failure, but also makes multiple therapeutic sessions unnecessary. [source] Abnormal venous and arterial patterning in chordin mutantsDEVELOPMENTAL DYNAMICS, Issue 9 2007Emmanuèle C. Délot Abstract Classic dye injection methods yielded amazingly detailed images of normal and pathological development of the cardiovascular system. However, because these methods rely on the beating heart of diffuse the dyes, the vessels visualized have been limited to the arterial tree, and our knowledge of vein development is lagging. In order to solve this problem, we injected pigmented methylsalicylate resins in mouse embryos after they were fixed and made transparent. This new technique allowed us to image the venous system and prompted the discovery of multiple venous anomalies in Chord,/, mutant mice. Genetic inactivation of Chordin, an inhibitor of the Bone Morphogenetic Protein signaling pathway, results in neural crest defects affecting heart and neck organs, as seen in DiGeorge syndrome patients. Injection into the descending aorta of Chrd,/, mutants demonstrated how a very severe early phenotype of the aortic arches develops into persistent truncus arteriosus. In addition, injection into the atrium revealed several patterning defects of the anterior cardinal veins and their tributaries, including absence of segments, looping and midline defects. The signals that govern the development of the individual cephalic veins are unknown, but our results show that the Bone Morphogenetic Protein pathway is necessary for the process. Developmental Dynamics 236:2586,2593, 2007. © 2007 Wiley-Liss, Inc. [source] Forest blowdown impacts of Hurricane Rita on fluvial systemsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2009Jonathan D. Phillips Abstract Hurricane Rita, a category three hurricane which struck the US Gulf Coast near the Louisiana/Texas border in 2005, did not cause extensive river flooding. However, the storm did result in extensive forest damage and tree blowdown. High-resolution post-storm aerial photography allowed an inventory of river bank trees blown into the channel along the lower Neches and Sabine Rivers of southeast Texas and southwest Louisiana. Blowdowns directly into the channel averaged 9·3 per kilometer in the lower Neches and 13·4 in the lower Sabine River, but individual reaches 10 to 20 km in length had rates of 20 to 44 blowdowns per kilometer. Though large woody debris (LWD) from Hurricane Rita was widely perceived to reduce the capacity of channels to convey flow, no strong evidence exists of increased flooding or significant reductions in channel conveyance capacity due to LWD from the storm. The Rita blowdown inventory also allowed an assessment of whether similar blowdown events could account for major logjams and rafts on Red, Atchafalaya, and Colorado Rivers on the Gulf Coast, which blocked navigation from tens to hundreds of kilometers in the 1800s. Results from Hurricane Rita suggest that blowdown into channels alone , not withstanding blowdown elsewhere in the river valleys or along tributaries which could deliver LWD to the river , is sufficient to completely block channels, thus providing a plausible mechanism for initiating such (pre)historic log rafts. Copyright © 2009 John Wiley & Sons, Ltd. [source] The behavior of specific sediment yield in different grain size fractions in the tributaries of the middle Yellow River as influenced by eolian and fluvial processesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2008Jiongxin Xu Abstract Based on data from 35 stations on the tributaries of the Yellow River, annual specific sediment yield (Ys) in eight grain size fractions has been related to basin-averaged annual sand,dust storm days (Dss) and annual precipitation (Pm) to reveal the influence of eolian and fluvial processes on specific sediment yield in different grain size fractions. The results show that Ys in fine grain size fractions has the highest values in the areas dominated by the coupled wind,water process. From these areas to those dominated by the eolian process or to those dominated by the fluvial process, Ys tends to decrease. For relatively coarse grain size fractions, Ys has monotonic variation, i.e. with the increase in Dss or the decrease in Pm, Ys increases. This indicates that the sediment producing behavior for fine sediments is different from that for relatively coarse sediments. The results all show that Ys for relatively coarse sediments depends on the eolian process more than on the fluvial process, and the coarser the sediment fractions the stronger the dependence of the Ys on the eolian process. The Ys,Dss and Ys,Pm curves for fine grain size fractions show some peaks and the fitted straight lines for Ys,Dss and Ys,Pm relationships for relatively coarse grain size fractions show some breaks. Almost all these break points may be regarded as thresholds. These thresholds are all located in the areas dominated by the coupled wind,water process, indicating that these areas are sensitive for erosion and sediment production, to which more attention should be given for the purpose of erosion and sediment control. A number of regression equations were established, based which the effect of rainfall, sand,dust storms and surface material grain size on specific sediment yield can be assessed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Downstream variation in bed sediment size along the East Carpathian rivers: evidence of the role of sediment sourcesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2008Maria R, doane Abstract Taking as an example six main rivers that drain the western flank of the Eastern Carpathians, a conceptual model has been developed, according to which fluvial bed sediment bimodality can be explained by the overlapping of two grain size distribution curves of different origins. Thus, for Carpathian tributaries of the Siret, coarse gravel joins an unimodal distribution presenting a right skewness with enhanced downstream fining. The source of the coarse material distributions is autohtonous (by abrasion and hydraulic sorting mechanisms). A second distribution with a sandy mode is, in general, skewed to the left. The source of the second distribution is allohtonous (the quantity of sand that reaches the river-bed through the erosion of the hillslope basin terrains). The intersection of the two distributions occurs in the area of the 0·5,8 mm fractions, where, in fact, the right skewness (for gravel) and left skewness (for sand) histogram tails meet. This also explains the lack of particles in the 0·5,8 mm interval. For rivers where fine sediment sources are low, the 0·5,8 mm fractions have a higher proportion than the fractions under 1 mm. For the Siret River itself, bed sediment bimodality is greatly enhanced due to the fact that the second mode is more than 25% of the full sample. As opposed to its tributaries, the source of the first mode, of gravel, is allohtonous to the Siret river, generated by the massive input of coarse sediment through the Carpathian tributaries, while the second mode, of the sands, is local. In this case we can also observe that the two distributions of particles of different origins overlap in the 0·5,8 mm fraction domain, creating the illusion of ,particle lack' in the fluvial bed sediments. Copyright © 2007 John Wiley & Sons, Ltd. [source] The use of short-lived radionuclides to quantify transitional bed material transport in a regulated riverEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2007Nira L. Salant Abstract We investigate the use of the short-lived fallout radionuclide beryllium-7 (7Be; t1/2 = 53·4 days) as a tracer of medium and coarse sand (0·25,2 mm), which transitions between transport in suspension and as bed load, and evaluate the effects of impoundment on seasonal and spatial variations in bed sedimentation. We measure 7Be activities in approximately monthly samples from point bar and streambed sediments in one unregulated and one regulated stream. In the regulated stream our sampling spanned an array of flow and management conditions during the annual transition from flood control in the winter and early spring to run-of-the-river operation from late spring to autumn. Sediment stored behind the dam during the winter quickly became depleted in 7Be activity. This resulted in a pulse of ,dead' sediment released when the dam gates were opened in the spring which could be tracked as it moved downstream. Measured average sediment transport velocities (30,80 metres per day (m d,1)) exceed those typically reported for bulk bed load transport and are remarkably constant across varied flow regimes, possibly due to corresponding changes in bed sand fraction. Results also show that the length scale of the downstream impact of dam management on sediment transport is short (c. 1 km); beyond this distance the sediment trapped by the dam is replaced by new sediment from tributaries and other downstream sources. Copyright © 2006 John Wiley & Sons, Ltd. [source] Stream geomorphology in a mountain lake district: hydraulic geometry, sediment sources and sinks, and downstream lake effectsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2007C. D. Arp Abstract Lakes are common in glaciated mountain regions and geomorphic principles suggest that lake modifications to water and sediment fluxes should affect downstream channels. Lakes in the Sawtooth Mountains, Idaho, USA, were created during glaciation and we sought to understand how and to what extent glacial morphology and lake disruption of fluxes control stream physical form and functions. First, we described downstream patterns in channel form including analyses of sediment entrainment and hydraulic geometry in one catchment with a lake. To expand on these observations and understand the role of glacial legacy, we collected data from 33 stream reaches throughout the region to compare channel form and functions among catchments with lakes, meadows (filled lakes), and no past or present lakes. Downstream hydraulic geometry relationships were weak for both the single catchment and regionally. Our data show that downstream patterns in sediment size, channel shape, sediment entrainment and channel hydraulic adjustment are explained by locations of sediment sources (hillslopes and tributaries) and sediment sinks (lakes). Stream reaches throughout the region are best differentiated by landscape position relative to lakes and meadows according to channel shape and sediment size, where outlets are wide and shallow with coarse sediment, and inlets are narrow and deep with finer sediment. Meadow outlets and lake outlets show similarities in the coarse-sediment fraction and channel capacity, but meadow outlets have a smaller fine-sediment fraction and nearly mobile sediment. Estimates of downstream recovery from lake effects on streams suggest 50 per cent recovery within 2,4 km downstream, but full recovery may not be reached within 20 km downstream. These results suggest that sediment sinks, such as lakes, in addition to sources, such as tributaries, are important local controls on mountain drainage networks. Copyright © 2006 John Wiley & Sons, Ltd. [source] Tilting neotectonics of the Guadiamar drainage basin, SW SpainEARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2004Josep M. SalvanyArticle first published online: 23 DEC 200 Abstract The Guadiamar river ,ows from the southern Iberian Massif to the Guadalquivir foreland basin, SW Spain. Its drainage basin displays asymmetries in the stream network, the arrangement of alluvial terraces and the con,guration of the trunk river valley. The stream network asymmetry was studied using morphometric measures of transverse topographic sym-metry, asymmetry factor and drainage basin shape. The alluvial terraces were studied through the lithologic logs of more than a hundred boreholes and ,eld mapping. The morphometric methods demonstrate a regional tectonic tilting toward the SSE, causing both the migration of the Guadiamar river toward the east and the migration of the Guadiamar tributaries toward the southwest. As a consequence of the Guadiamar river migration, an asymmetric valley developed, with a steep eastern margin caused by river dissection, and a gentle western margin where the main alluvial deposits are found. The ages obtained using the 14C analysis of samples from several alluvial deposits show that the river migration, and thus tilting, has occurred during the Holocene as well as earlier in the Quaternary. This interpretation revises the Guadiamar longitudinal fault assumed by previous studies. Copyright © 2003 John Wiley & Sons, Ltd. [source] Processes and forms of an unstable alluvial system with resistant, cohesive streambeds ,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2002Andrew Simon Abstract As a response to channelization projects undertaken near the turn of the 20th century and in the late 1960s, upstream reaches and tributaries of the Yalobusha River, Mississippi, USA, have been rejuvenated by upstream-migrating knickpoints. Sediment and woody vegetation delivered to the channels by mass failure of streambanks has been transported downstream to form a large sediment/debris plug where the downstream end of the channelized reach joins an unmodified sinuous reach. Classification within a model of channel evolution and analysis of thalweg elevations and channel slopes indicates that downstream reaches have equilibrated but that upstream reaches are actively degrading. The beds of degrading reaches are characterized by firm, cohesive clays of two formations of Palaeocene age. The erodibility of these clay beds was determined with a jet-test device and related to critical shear stresses and erosion rates. Repeated surveys indicated that knickpoint migration rates in these clays varied from 0·7 to 12 m a,1, and that these rates and migration processes are highly dependent upon the bed substrate. Resistant clay beds of the Porters Creek Clay formation have restricted advancement of knickpoints in certain reaches and have caused a shift in channel adjustment processes towards bank failures and channel widening. Channel bank material accounts for at least 85 per cent of the material derived from the channel boundaries of the Yalobusha River system. Strategies to reduce downstream flooding problems while preventing upstream erosion and land loss are being contemplated by action agencies. One such proposal involves removal of the sediment/debris plug. Bank stability analyses that account for pore-water and confining pressures have been conducted for a range of hydrologic conditions to aid in predicting future channel response. If the sediment/debris plug is removed to improve downstream drainage, care should be taken to provide sufficient time for drainage of groundwater from the channel banks so as not to induce accelerated bank failures. Published in 2002 John Wiley & Sons, Ltd. [source] Influences of the vegetation mosaic on riparian and stream environments in a mixed forest-grassland landscape in "Mediterranean" northwestern CaliforniaECOGRAPHY, Issue 4 2005Hartwell H. Welsh We examined differences in riparian and aquatic environments within the three dominant vegetation patch types of the Mattole River watershed, a 789-km2 mixed conifer-deciduous (hardwood) forest and grassland-dominated landscape in northwestern California, USA. Riparian and aquatic environments, and particularly microclimates therein, influence the distributions of many vertebrate species, particularly the physiologically-restricted ectotherms , reptiles and amphibians (herpetofauna), and fishes. In addition to being a significant portion of the native biodiversity of a landscape, the presence and relative numbers of these more tractable small vertebrates can serve as useful metrics of its "ecological health." Our primary objective was to determine the range of available riparian and aquatic microclimatic regimes, and discern how these regimes relate to the dominant vegetations that comprise the landscape mosaic. A second objective, reported in a companion paper, was to examine relationships between available microclimatic regimes and herpetofaunal distributions. Here we examined differences in the composition, structure, and related environmental attributes of the three dominant vegetation types, both adjacent to and within the riparian corridors along 49 tributaries. Using automated dataloggers, we recorded hourly water and air temperatures and relative humidity throughout the summer at a representative subset of streams; providing us with daily means and amplitudes for these variables within riparian environments during the hottest period. Although the three vegetation types that dominate this landscape each had unique structural attributes, the overlap in plant species composition indicates that they represent a seral continuum. None-the-less, we found distinct microclimates in each type. Only riparian within late-seral forests contained summer water temperatures that could support cold-water-adapted species. We evaluated landscape-level variables to determine the best predictors of water temperature as represented by the maximum weekly maximum temperature (MWMT). The best model for predicting MWMT (adj. R2=0.69) consisted of catchment area, aspect, and the proportion of non-forested (grassland) patches. Our model provides a useful tool for management of cold-water fauna (e.g. salmonids, stream amphibians) throughout California's "Mediterranean" climate zone. [source] Linking upstream channel instability to downstream degradation: Grenada Lake and the Skuna and Yalobusha River Basins, MississippiECOHYDROLOGY, Issue 3 2009Sean J. Bennett Abstract Unstable fluvial systems are characterized by actively migrating knickpoints, incising channel beds, failing banks, and recruitment of large woody debris and it would appear that river corridors downstream of these processes would be adversely affected or impaired because of higher fluxes of sediment and other riverine products. In north-central Mississippi, the Yalobusha River is one such system and the characteristics of two downstream locations are examined to explore this geomorphic linkage between upstream instability and downstream degradation. For the large woody debris plug along the Yalobusha River, it is found that (1) the deposit is composed mostly of sand covered with a veneer of silt and clay, (2) agrichemicals and enriched concentrations of elements are prevalent, and (3) excessive sedimentation and wood accumulation have forced river flow entirely out-of-bank. For Grenada Lake, it is found that (1) the impounded sediment is predominantly clay, (2) agrichemicals and elements observed throughout the reservoir show no spatial variation, (3) little difference exists in the amount and quality between the sediments deposited in Skuna and Yalobusha River arms, and (4) only a small fraction of the reservoir's storage capacity has been lost because of sedimentation. While excessive sedimentation and large woody debris recruitment have had a marked affect on stream corridor function in the area of the debris plug, the high sediment loads associated with the unstable portions of the Yalobusha River and their associated products have not been communicated to Grenada Lake. The fish consumption advisories within Grenada Lake and its tributaries due to bioaccumulated trace elements and agrichemicals, appear to be independent of the pervasive river channel instability occurring upstream. Copyright © 2009 John Wiley & Sons, Ltd. [source] Tributaries influence recruitment of fish in large riversECOLOGY OF FRESHWATER FISH, Issue 4 2009B. M. Pracheil Abstract,,, Recent work demonstrates that tributary inputs are important community reorganisation points for river biota; however, no studies have examined the long-term effects of tributary inputs on fish population dynamics. This study examines nearly 40 years of young-of-year (yoy) paddlefish recruitment data to investigate the hypothesis that tributaries influence mainstem fish population dynamics. We generated hydrological variables from daily mean flow data (1965,2007) from an impounded reach of the mainstem Missouri River and from the Niobrara River, a relatively unaltered tributary, using Indicators of Hydrologic Alteration software. Three multiple regression models using natural-log transformed catch per unit effort (log cpue) as the response variable were created using (1) Missouri River-only flow variables, (2) Niobrara River-only flow variables and (3) Missouri River and Niobrara River flow variables. Flow variables from the Niobrara River explain a greater proportion of yoy paddlefish log cpue variability demonstrating that tributaries can positively impact fish population dynamics in altered rivers. [source] Contemporary egg size divergence among sympatric grayling demes with common ancestorsECOLOGY OF FRESHWATER FISH, Issue 1 2008F. Gregersen Abstract, This study documents divergence in egg size that has occurred over less than 25 generations among sympatric demes of European grayling (Thymallus thymallus) from Lake Lesjaskogsvatnet in Norway. A cluster analysis identified two clusters of tributaries: one of small, warm tributaries (SW) and the other of large, cold tributaries (LC). Spawning occurs more regularly and up to 4 weeks earlier in SW tributaries compared with that in LC ones. We explored numerous mixed models predicting egg size from year (random effect), basin and tributary (fixed effects), and female length. The most supported model estimated length-adjusted egg size to be larger in SW tributaries compared with that in LC tributaries. Combinations of density-dependent (competition for food/space) and density-independent (temperature) factors along with phenotypic plasticity and maternal effects are discussed as potential differentiation sources. We suggest high temperatures (increased metabolism) to reinforce the selective advantage of large eggs under conditions with highly density-dependent fry interactions. [source] Spatial and temporal variations of two cyprinids in a subtropical mountain reserve , a result of habitat disturbanceECOLOGY OF FRESHWATER FISH, Issue 3 2007C.-C. Han Abstract,,, We investigated the variations of population of two cyprinids, Varicorhinus alticorpus and Varicorhinus barbatulus, using long-term survey data (1995,2004) in the subtropical island of Taiwan. Fish abundance data showed that at the mainstem stations, V. barbatulus which used to dominate in the higher altitude had declined significantly, while V. alticorpus that used to occupy only the lower altitude had spread upward. However, at the tributaries, trend of the populations of V. barbatulus were not significantly different over time, while populations of V. alticorpus were absent at higher altitude but began to increase at lower altitude. Environmental parameters revealed that sporadic high turbidity was observed at the mainstem stations, but not at the tributaries. Images taken before and after typhoon also showed habitat destruction by debris flow at the mainstem stations. As some models predicted that suitable fish habitats will shrink because of increasing water temperature due to global warming, we showed that fish distribution may be affected by habitat disturbance due to intensified storms sooner than the actual increase of water temperature. [source] Egg size differentiation among sympatric demes of brown trout: possible effects of density-dependent interactions among fryECOLOGY OF FRESHWATER FISH, Issue 3 2006F. Gregersen Abstract,,, This study investigates differentiation in egg size among five sympatric brown trout (Salmo trutta (L.)) demes. We explore a hypothesis predicting high density-dependent interactions among juveniles to favour large eggs by sampling closely located (<100 m) deme pairs with low and high fry abundances. A mancova model fitted the egg size versus egg number relationship as a function of large-scale spatial habitat heterogeneity (basin) and maternal phenotype revealed that demes have significantly different egg size versus fecundity relationships and that the differentiation is mainly due to interdeme variation in egg size. Fry density was significantly and positively associated with egg size and a post-hoc test indicated egg size to be significantly greater in high-density than low-density tributaries. The data is consistent with the density-dependent hypothesis and suggest that reproductive investment can diverge over small geographic distances, potentially in response to environments favouring greater investment in offspring quality. [source] Effect of habitat fragmentation on spawning migration of brown trout (Salmo trutta L.)ECOLOGY OF FRESHWATER FISH, Issue 3 2006C. Gosset Abstract , Human-induced habitat alteration is one of the main causes of the decline of freshwater fish populations. The watershed of the River Bidasoa (Spain) is an example of heavily fragmented habitat. The local brown trout (Salmo trutta L.) population is disturbed, with evidence of poor recruitment as well as low adult densities in the main stem. Forty male and female adult migratory trout were tagged with external or internal radio transmitters and released. Fixed stations with data loggers and mobile antennae were used with daily surveys to track fish movements during the migration and spawning period (3 months). Migration distances did not exceed 10 km, and half of the fish never entered a tributary in the study area. Fragmentation because of weirs on the main stem apparently prevented fish from reaching their spawning destination. Fish that entered the tributaries were first confronted with an accessibility problem because of low discharge. However, each fish chose one tributary, without making attempts to run up in other tributaries. Once in the tributary, fish were restrained in their upstream movements by dams. The study area appeared to be isolated from the vast upper part of the watershed. Within the study area, upper parts of tributaries also seemed strongly disconnected from the main stem. This study illustrates the negative impact of river fragmentation on S. trutta migration pattern. Population sustainability can be directly affected through the low availability of spawning grounds for migratory fish. Long-term effects of fragmentation may cause reproductive isolation within watersheds, which in the case of trout also means isolated phenotypic population units. [source] Threatened obligatory riverine fishes in human-modified Polish riversECOLOGY OF FRESHWATER FISH, Issue 1-2 2000T. Penczak Abstract , The fate of obligatory riverine fish species (rheophils), which are the objects of anglers' exploitation (chub ,Leuciscus cephalus, nase ,Chondrostoma nasus, barbel ,Barbus barbus, gudgeon ,Gobio gobio), and brown trout (Salmo trutta m. fario) and grayling (Thymallus thymallus) (in the Gwda River basin only), were investigated in large alluvial rivers (Pilica and Warta) and in the medium-sized Gwda River basin. The Pilica (1973) and the Warta (1986,1987) were divided by large dams without fish ladders in their middle courses. The Gwda River was divided by only a few dams along its course, but its tributaries carrying pure water had numerous small dams that supplied water for fish farms. Other stresses influencing fish populations in these rivers were: pollution, overfishing, hydroelectric plants and bank revetments. Because the listed stresses occurred alternately and at various periods of time in these rivers, this enabled attributing the cause for extinction and reduction of the abundance and distribution. In the salmon Gwda River basin, a drastic decrease in spatial distribution and reduction of occurrence ranges of brown trout, grayling and barbel was evident in respect to the first study period (1980s) in the 1990s. In the large, alluvial Pilica River, nase, barbel and dace are on the edge of extinction and chub and gudgeon are vulnerable. In the Warta's tailwater, barbel is an extinct species, and chub, dace and gudgeon are vulnerable ones. In a site in the backwater, none of the above mentioned species became extinct, but their abundance and occurrence frequency decreased a bit in respect to the pre-impoundment period. Roach-generalist, which was used in this research as a "control" species, increased in abundance in all 3 rivers. These investigations univocally proved that the dams cause catastrophic stress for obligatory riverine species., [source] Agricultural pesticides and selected degradation products in five tidal regions and the main stem of Chesapeake Bay, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2007Laura L. McConnell Abstract Nutrients, sediment, and toxics from water sources and the surrounding airshed are major problems contributing to poor water quality in many regions of the Chesapeake Bay, an important estuary located in the mid-Atlantic region of the United States. During the early spring of 2000, surface water samples were collected for pesticide analysis from 18 stations spanning the Chesapeake Bay. In a separate effort from July to September of 2004, 61 stations within several tidal regions were characterized with respect to 21 pesticides and 11 of their degradation products. Three regions were located on the agricultural Delmarva Peninsula: The Chester, Nanticoke, and Pocomoke Rivers. Two regions were located on the more urban western shore: The Rhode and South Rivers and the Lower Mobjack Bay, including the Back and Poquoson Rivers. In both studies, herbicides and their degradation products were the most frequently detected chemicals. In 2000, atrazine and metolachlor were found at all 18 stations. In 2004, the highest parent herbicide concentrations were found in the upstream region of Chester River. The highest concentration for any analyte in these studies was for the ethane sulfonic acid of metolachlor (MESA) at 2,900 ng/L in the Nanticoke River. The degradation product MESA also had the greatest concentration of any analyte in the Pocomoke River (2,100 ng/L) and in the Chester River (1,200 ng/L). In the agricultural tributaries, herbicide degradation product concentrations were more strongly correlated with salinity than the parent herbicides. In the two nonagricultural watersheds on the western shore, no gradient in herbicide concentrations was observed, indicating the pesticide source to these areas was water from the Bay main stem. [source] Assessing trace-metal exposure to American dippers in mountain streams of southwestern British Columbia, CanadaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2005Christy A. Morrissey Abstract To develop a suitable biomonitor of metal pollution in watersheds, we examined trends in exposure to nine trace elements in the diet (benthic invertebrates and fish), feathers (n = 104), and feces (n = 14) of an aquatic passerine, the American dipper (Cinclus mexicanus), from the Chilliwack watershed in British Columbia, Canada. We hypothesized that key differences may exist in exposure to metals for resident dippers that occupy the main river year-round and altitudinal migrants that breed on higher elevation tributaries because of differences in prey metal levels between locations or possible differences in diet composition. Metals most commonly detected in dipper feather samples in decreasing order were Zn > Cu > Hg > Se > Pb > Mn > Cd > Al > As. Resident dipper feathers contained significantly higher mean concentrations of mercury (0.64 ,g/g dry wt), cadmium (0.19 ,g/g dry wt), and copper (10.8 ,g/g dry wt) relative to migrants. Mass balance models used to predict daily metal exposure for dippers with different diets and breeding locations within a watershed showed that variation in metal levels primarily was attributed to differences in the proportion offish and invertebrates in the diet of residents and migrants. In comparing predicted metal exposure values to tolerable daily intakes (TDI), we found that most metals were below or within the range of TDI, except selenium, aluminum, and zinc. Other metals, such as cadmium, copper, and arsenic, were only of concern for dippers mainly feeding on insects; mercury was only of concern for dippers consuming high fish diets. The models were useful tools to demonstrate how shifts in diet and breeding location within a single watershed can result in changes in exposure that may be of toxicological significance. [source] Monitoring river sediments contaminated predominantly with polyaromatic hydrocarbons by chemical and in vitro bioassay techniquesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2001Jan Vondrá Abstract Extracts of sediment samples collected from the Morava River and its tributaries (Czech Republic) were examined for mutagenic, dioxin-like, and estrogenic activities. Moreover, the human leukemic HL-60 cell line was tested as a potential model for the detection of effects of environmental contaminants on cell proliferation and differentiation processes. Analytical data indicate that the sediments were contaminated predominantly with polycyclic aromatic hydrocarbons (PAHs) and phthalate esters. The sums of concentrations of 16 U.S. Environmental Protection Agency priority PAHs ranged from 0.8 to 13.2 ,g/g and those of phthalates reached up to 3,000 ng/g, while only low levels of chlorinated hydrocarbons were found. The main goal of the present study was to determine effects of PAH prevalence on in vitro bioassays, with special emphasis on dioxin-like activity. The dioxin-like activity was tested using a reporter gene assay based on chemical-activated luciferase expression (the CALUX assay). Significant dioxin-like activity (2.6,40.1 ,g/g benzo[a]pyrene equivalents and 5.9,48.2 ng/g 2,3,7,8-tetrachlorodibenzo- p -dioxin equivalents) was detected in all samples, and the results obtained with various exposure times or with both crude and PAH-deprived extracts indicate that the response was probably caused almost exclusively by the presence of high concentrations of PAHs. This corresponds with results of chemical analyses and indicates that various exposure times would allow a discrimination between dioxin-like activities of persistent compounds and easily metabolized aryl hydrocarbon (Ah) receptor inducers. Only sediment extracts containing the highest concentrations of PAHs were mutagenic, as determined by the umu assay. Estrogenic activity was found in several samples (4.75,22.61 pg/g estradiol equivalents) using cells stably transfected with an estrogen-responsive element linked to a luciferase promoter. Noncytotoxic doses of extracts had no effects on HL-60 cell proliferation, while two of the tested crude extracts significantly enhanced their all- trans retinoic acid-induced differentiation. These activities were not associated with phthalate esters and/or PAHs. Our results indicate that cellular and biochemical in vitro assays based on various specific modes of action may yield data complementary to results of mutagenicity tests and that they could be useful in environmental risk assessment. High levels of PAHs are apparently associated with dioxin-like and mutagenic activities rather than with estrogenic activity. [source] CONTEMPORARY ISOLATION-BY-DISTANCE, BUT NOT ISOLATION-BY-TIME, AMONG DEMES OF EUROPEAN GRAYLING (THYMALLUS THYMALLUS, LINNAEUS) WITH RECENT COMMON ANCESTORSEVOLUTION, Issue 2 2009Nicola J. Barson The development of isolation by distance (IBD) and isolation by time (IBT) was contrasted among demes of European grayling (Thymallus thymallus) that have diverged within the last 25 generations following colonization of a lake (Lesjaskogsvatnet). We find low but significant levels of genetic differentiation among spawning tributaries and a pattern of IBD among them. We do not, however, find evidence for IBT despite an up to four-week difference in spawning date between "warm/early" and "cold/late" spawning demes and differences in the incubation temperatures experienced by offspring. It appears that IBD has developed more rapidly than IBT in this system and that adaptive divergence has been initiated in the absence of IBT. Although analysis of selected loci could reveal reduced recombination in parts of the genome associated with temporal divergence, our analysis of neutral genetic data suggests that IBD is a more important isolating mechanism in the early stages of adaptive divergence in European grayling. [source] Snorkelling as a method for assessing spawning stock of Atlantic salmon, Salmo salarFISHERIES MANAGEMENT & ECOLOGY, Issue 3 2007P. ORELL Abstract, Reliability of underwater snorkel counts of adult Atlantic salmon, Salmo salar L., was analysed in the tributaries of the River Teno, close to the spawning period. In small (width 5,20 m) rivers, the replicated total counts of salmon were reasonably precise (CV = 5.4,8.5%), while in the medium-sized river (width 20,40 m) the precision of the counting method was considerably lower (CV = 15.3%). Low precision in a medium sized river was also observed in an experiment using marked live fish where the observation efficiency varied between 36.4% and 70.0%. In a small river, the detection efficiency of artificial fish silhouettes (test salmon) was almost perfect in pools (98%), but decreased in rapids (84%). Separate counts of males, females, grilse and large salmon were usually more variable than total counts, indicating that divers were more capable of locating a fish than properly identifying its sex and sea-age. The behaviour of adult salmon was favourable to conduct snorkel counts, as fish normally stayed still, or after hesitating, moved upstream (>95%of the cases) when encountering a diver. The high observation efficiency (>90%) and precision, favourable behaviour of salmon and congruence between snorkel counts and catch statistics in small rivers suggest that reliable data on Atlantic salmon spawning stock can be collected by snorkeling provided that the environmental conditions are suitable and the divers are experienced. [source] Blue sucker stock characteristics in the upper Yazoo River basin, Mississippi, USAFISHERIES MANAGEMENT & ECOLOGY, Issue 3 2003G. R. Hand Abstract Blue sucker Cycleptus elongatus (L.) in the upper Yazoo River basin, Mississippi, USA was studied using overnight hoop net sets (n = 4093) during 1988 and 1990,1998 to determine the influence of channel dredging. There were 264 blue suckers captured, ranging from 3 to 11 years of age. Length ranged from 265 to 700 mm and weight from 120 to 4700 g. Concurrent studies with smaller mesh hoop nets failed to capture any juvenile blue suckers. Catch-per-unit-effort (CPUE: fish net,1) declined throughout the study in the Yalobusha River, a river subjected to channel dredging during 1988 and 1994. With the exception of limited hydraulic dredging in the Tallahatchie River, there was no dredging in the other Yazoo River tributaries, nor were there declines in blue sucker catch rates in these rivers. Throughout the upper Yazoo River basin, blue sucker stocks were dominated by adult fish, and there was little evidence of reproduction or recruitment. Conservation of the blue sucker in the upper Yazoo River basin should include actions that ensure the functional integrity of this floodplain river ecosystem and elimination of channel dredging throughout the basin. [source] The effects of the net fishery closure on angling catch in the River Hvítá, IcelandFISHERIES MANAGEMENT & ECOLOGY, Issue 2 2003S. M. Einarsson Abstract Between 1991 and 2000, angling associations on the tributaries of the River Hvítá leased net fishery rights in the Hvítá mainstem, with the aim of eliminating net fishery harvest and improving the rod catch. The rod catch and net catch in the Hvítá system were significantly correlated (r = 0.94; P <,0.001) over the 10-year period prior to (1981,1990) closure of the net fishery. The rod fishery in the tributaries of the River Hvítá was also significantly correlated to the rod fishery in selected groups of rivers in west (r = 0.80; P < 0.01) and north (r = 0.73; P < 0.05) before the closure. Significant increases (P < 0.01) were observed in rod catches in the Hvítá tributaries between 1991 and 2000 after the closure, while rod catches in control regions decreased. Based on evaluation of rod catch trends before and after the closure, it was estimated that the net fishery lease increased rod catches in the tributaries between 1773 and 2175 fish (28,35%). The increase in rod catches also suggested that the rod fishery may be taking 39,52% of the estimated previous net catch. The high price paid annually for the net fishery lease just to eliminate net fishing (,135 000) reflects the high value of rod caught salmon compared with salmon caught by the net fishery. [source] Local and ecoregion effects on fish assemblage structure in tributaries of the Rio Paraíba do Sul, BrazilFRESHWATER BIOLOGY, Issue 12 2009BENJAMIN CARVALHO TEIXEIRA PINTO Summary 1.,We examined the effects of physical and chemical habitat variables and ecoregions on species occurrence and fish assemblage structure in streams of the Paraíba do Sul basin, in southeast Brazil. 2.,Fish and environmental data were collected from 42 sites on 26 first to fourth order streams (1 : 50 000 map scale) in three ecoregions. The sites occurred in one valley and two plateau ecoregions at altitudes of 40,1080 m and distances of 0.1,188 km from the main channel of the Rio Paraíba do Sul. Physical habitat (substratum, riparian cover, habitat types) and water quality (dissolved oxygen, pH, temperature and conductivity) variables were measured at each sampling site. 3.,A total of 2684 individuals in 16 families and 59 species were recorded. 4.,Ecoregion was a better predictor of the fish assemblage than the other environmental variables, according to the differences between the mean within-class and mean between-class similarities in assemblage data. 5.,Differing landscape characteristics were associated with differing local variables and thereby with differing fish assemblage structures. Riffles, shrub, grass, dissolved oxygen, conductivity and temperature were closely related to fish assemblage structure. 6.,Fish assemblages in sites far from the main river and at higher altitudes also differed from those near the Paraíba do Sul main channel, presumably as a result of differences in connectivity, covarying environmental factors and anthropogenic influence. 7.,These results reinforce the importance of understanding how stream communities are influenced by processes and patterns operating at local and regional scales, which will aid water resource managers to target those factors in their management and rehabilitation efforts. [source] Predator,prey interactions in river networks: comparing shrimp spatial refugia in two drainage basinsFRESHWATER BIOLOGY, Issue 3 2009ALAN P. COVICH Summary 1.,Analysis of drainage networks provides a framework to evaluate the densities and distributions of prey species relative to locations of their predators. Upstream migration by diadromous shrimp (Atya lanipes and Xiphocaris elongata) during their life cycle provides access to headwater refugia from fish predation, which is intense in estuaries and coastal rivers. 2.,We postulate that geomorphic barriers (such as large, steep waterfalls >3.5 m in height), can directly limit the distribution of predatory fishes and, indirectly, affect the densities of their prey (freshwater shrimps) in headwater streams. 3.,We compared densities of shrimp in pools above and below waterfalls, in four headwater tributaries in two river basins of the Luquillo Mountains of northeastern Puerto Rico. We measured shrimp densities twice a year over 8 years (1998,2005) in Prieta, Toronja, Bisley 3 and Bisley 5 streams, which differ in drainage network positions relative to steep waterfalls in Río Espíritu Santo and Río Mameyes. 4.,Predatory fishes are absent in the Prieta and Toronja pools and present in Bisely 3 and in lower Bisley 5 pools. Atya lanipes and X. elongata rarely occur in the Bisley streams where predatory fishes are present but these shrimps are abundant in Prieta and Toronja, streams lacking predatory fishes. 5.,The mean carapace length of X. elongata is longer in pools where fish are present (Bisley 3 and lower Bisley 5) than in pools lacking fish (Prieta, Toronja, Upper Bisley 5). The increased body size is primarily due to significantly longer rostrums of individuals in stream reaches with fish (below waterfall barriers) than in those reaches lacking fish (above waterfall barriers). Rostrum length may be an adaptation to avoid predation by visually feeding fishes. 6.,Atya lanipes and X. elongata distributions and densities were predicted primarily by drainage network position relative to the presence or absence of predatory fishes. High, steep waterfalls effectively impeded fish from moving upstream and created a spatial refuge. Xiphocaris elongata may rely on size refugia (longer rostrum) to minimize predation where spatial refugia are lacking. [source] | |||||||||||||||||||||||||||||||||||||