scholarly journals Stability and spatio-temporal structure in fish assemblages of two floodplain lagoons of the lower Orinoco River

2009 ◽  
Vol 7 (4) ◽  
pp. 719-736 ◽  
Author(s):  
Nirson González ◽  
Carlos Lasso ◽  
Judith Rosales
Keyword(s):  
Aquatic Vegetation ◽  
Fish Assemblages ◽  
Hydrological Cycle ◽  
Temporal Structure ◽  
Biotic Interactions ◽  
High Water ◽  
Water Phase ◽  
Fish Assemblage Structure ◽  
Biological Interactions ◽  
The Mean

Fish assemblage structure and variability were analyzed in two floodplain lagoons (Las Arhuacas and Los Cardonales) along the lower Orinoco over a hydrological cycle. Every three months during continuous three-day sampling, experimental gill nets (5 to 12.5 cm of mesh opening) and 1 mm-mesh seine nets were utilized according to the types of habitats presents. A total of 133 fish species were found in Las Arhuacas and 95 species in Cardonales. Fifty five and 17 species were exclusive to Las Arhuacas and Los Cardonales respectively, and 77 were common to both lagoons. In Las Arhuacas, the most speciesrich orders were Characiformes, Siluriformes, Perciformes and Gymnotiformes and in Los Cardonales, the most species-rich orders were Characiformes, Siluriformes, Clupeiformes and Perciformes. The richness, abundance and biomass were significantly higher (p < 0.001) in Arhuacas than in Cardonales. In general, the fishes assemblage was highly variable during the high water phase and moderately stable during low water phase in both lagoons, with more stability or less variability in Cardonales than Arhuacas. Also, there were significant differences in the fish assemblages between the two lagoons, mainly during low waters (ANOSIM; p < 0.001). The species that contributed most to the mean dissimilarity between the lagoons were Hypostomus argus, Aphanotorulus ammophilus, Potamorhina altamazonica, Prochilodus mariae, Loricaria gr. cataphracta, Oxydoras sifontesi, Hydrolycus armatus, Hyphopthalmus edentatus and Pterodoras rivasi. The last four species were more commonly collected in Los Cardonales. Also, the species of small size (mainly SL < 5 cm) such as Rhinosardinia amazonica, Moenkhausia sp. 1 "lepidura", Moenkhausia sp. 2, Aphyocharax alburnus, Characidium sp. 1, Moenkhausia sp. 3, Exodon paradoxus and Roeboides dientonito contributed to the mean dissimilarity among the beach and aquatic vegetation habitats. The patterns of the species assemblage organization were related to the dynamics of the floods. Non-random (i. e., deterministic) associations between species caused by the selection of habitats and/or to biological interactions, apparently were more common during low waters when there is an increased density of fish and so the biotic interactions are intensified. Stochastic associations, on the other hand, seemed to be more common during high water when species are more dispersed.

scholarly journals An assessment of the factors determining rotifer assemblage in river-lake systems: the effects of seasonality and habitat

2019 ◽  
Vol 36 ◽  
pp. 1-5
Author(s):  
Moacyr Serafim-Júnior ◽  
Gilmar Perbiche-Neves ◽  
Fabio Lansac-Toha
Keyword(s):  
Species Richness ◽  
Aquatic Macrophytes ◽  
Hydrological Cycle ◽  
High Water ◽  
Water Levels ◽  
Natural Environments ◽  
Ecological Attributes ◽  
Lake System ◽  
The Mean ◽  
Lake Systems

Zooplankton exhibit several trends of variation in space and time, and these trends can be more evident in natural environments without anthropic perturbations. Examples of anthropic factors are climate change, eutrophication and construction of reservoirs. This study evaluated the influence of three factors – seasonality, type of environment and the presence of aquatic macrophytes – on various ecological attributes of rotifers in a river-lake system located in the Paraná River floodplain. Monthly samplings were conducted during 1993 and 1994. The mean species richness per sample was 60 species. The seasonality and the type of environment influenced the ecological attributes of rotifer assemblages, while the presence or absence of aquatic macrophytes did not. Species richness was highest in the lake system and during the months when water levels were low. Multivariate analysis indicates a small group of species associated with the low water-level phase. In contrast, many species were associated with high water levels or increasing water levels. The seasonal variation of hydrological cycle and the type of environment are the most important factors for rotifer structure in natural conditions.

scholarly journals Factors determining the structure of fish assemblages in Tarumã River, Jaru Biological Reserve, Machado River drainage, northern Brazil

2021 ◽  
Vol 19 (4) ◽  
Author(s):  
Igor D. Costa ◽  
Natalia N. Santos Nunes ◽  
Carlos E. C. Freitas
Keyword(s):  
Species Composition ◽  
Environmental Variables ◽  
Fish Assemblages ◽  
Hydrological Cycle ◽  
Principal Component ◽  
High Water ◽  
Environmental Data ◽  
Partial Redundancy Analysis ◽  
The Individual ◽  
Biological Reserve

ABSTRACT Few studies on fish assemblages and relations with environmental factors in aquatic systems in southeastern Amazonia have been carried out when compared to other areas in the Amazon. Therefore, which are the main environmental variables and processes responsible for structuring them remains unknown. We hypothesized that fish assemblages respond the variation in the physical-chemistry variables between seasons of the hydrological cycle in a pristine river in the Amazon. The study was performed on fish assemblages of the Tarumã River, Jaru Biological Reserve, Rondônia. Samplings were carried out in five sites along the river in March and September, 2015, which included fish collection and environmental data measurements. Principal component analysis was performed to ordinate the sites in high water and low water seasons, according to environmental variables. We used a similarity analysis in order to identify the individual contribution of species in hydrological period and a partial redundancy analysis for quantify the relative importance of environmental variables in the species composition. As predicted by our hypothesis, the species composition was influenced by dissolved oxygen and temperature. Myloplus rubripinnis, Serrasalmus compressus, and S. rhombeus were the most abundant during high water, while S. rhombeus, Myloplus lobatus, Prochilodus nigricans, and Hydrolycus armatus were the dominant species during the low water.

scholarly journals Fish assemblage structure is consistent through an annual hydrological cycle in habitats of a floodplain-lake in the Colombian Amazon

2008 ◽  
Vol 6 (2) ◽  
pp. 257-266 ◽  
Author(s):  
Sandra Bibiana Correa
Keyword(s):  
Fish Assemblages ◽  
Hydrological Cycle ◽  
Oxbow Lake ◽  
Fish Assemblage Structure ◽  
Seasonal Fluctuations ◽  
Habitat Types ◽  
Flooded Forests ◽  
Colombian Amazon ◽  
Shrub Patches ◽  
Habitat Affinity

I investigated changes in abundance and spatial distribution of medium- and large-sized fishes (>100 mm) in an oxbow lake of the lower Apaporis River, Colombian Amazon, across three seasons (falling, low, and rising water). Fifty-three species in 13 families were collected from six habitats: lagoon channels, stream, flooded forests, isolated shrub patches, muddy beaches, and rocks. Abundance, biomass, and species richness were higher during the rising-water season and lower during falling-water season. Correspondence analysis (CA) showed that fish assemblages were associated to two basic habitat types. One assemblage of fishes was associated with densely vegetated and structurally complex habitats (flooded forest, lagoon channels, stream, and isolated shrub patches), and a second assemblage of fishes was associated with muddy beaches. These assemblages persisted despite seasonal fluctuations in water level. Species in the structurally complex habitats assemblage were mostly omnivores, whereas the beach habitat assemblage included mainly piscivores and detritivores. Results from this study suggest that overall abundance of fishes in habitats within and surrounding Taraira Lake is highly variable among seasons, but species habitat affinity is maintained through seasons.

scholarly journals Transformation of the Flow Regime of a Large Allochthonous River in Central Europe—An Example of the Vistula River in Poland

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 507 ◽  
Author(s):  
Dariusz Wrzesiński ◽  
Leszek Sobkowiak
Keyword(s):  
Flow Regime ◽  
Annual Cycle ◽  
River Flow ◽  
Hydrological Cycle ◽  
Temporal Structure ◽  
Flow Characteristics ◽  
Point Of View ◽  
Theoretical Point ◽  
Vistula River ◽  
Basin Water

Identification of river flow regime and its possible changes caused by natural factors or human activity is one of major issues in modern hydrology. In such studies different approaches and different indicators can be used. The aim of this study is to determine changes in flow regime of the largest river in Poland—the Vistula, using new, more objectified coefficients and indices, based on data recorded in 22 gauges on the Vistula mainstream and 38 gauges on its tributaries in the multi-year period 1971–2010. The paper consists of three main parts: in the first part, in order to recognize changes in the flow regime characteristics along the Vistula, data from gauges located on the river mainstream were analyzed with the help of the theory of entropy. In the second part gauging stations on the Vistula mainstream and its tributaries were grouped; values of the newly introduced pentadic Pardé’s coefficient of flow (discharge) (PPC) were taken as the grouping criterion. In the third part of the study a novel method of determining river regime characteristics was applied: through the recognition of the temporal structure of hydrological phenomena and their changes in the annual cycle sequences of hydrological periods (characteristic phases of the hydrological cycle) on the Vistula River mainstream and its tributaries were identified and their occurrence in the yearly cycle was discussed. Based on the detected changes of the 73-pentad Pardé’s coefficients of flow four main types of rivers were distinguished. Transformation of the flow regime was reflected in the identified different sequences of hydrological periods in the average annual cycle. It was found that while transformation of the Vistula River regime occurred along its whole course, the most frequent changes were detected in its upper, mountainous reaches, under the influence of the flow characteristics of its tributaries. This allowed the Vistula to be considered the allochthonous river. These findings are interesting not only from a theoretical point of view, but they also can be valuable to stakeholders in the field of the Vistula River basin water management and hydrological forecasting, including flood protection, which has recently become a matter of growing concern due to the observed effects of climate change and human impact.

scholarly journals Interconnectedness during high water maintains similarity in fish assemblages of island floodplain lakes in the Amazonian Basin

2010 ◽  
Vol 27 (6) ◽  
pp. 931-938 ◽  
Author(s):  
Carlos Edwar de C. Freitas ◽  
Flávia K. Siqueira-Souza ◽  
Alan Rezk Guimarães ◽  
Fabiane A. Santos ◽  
Ivanildo L.A. Santos
Keyword(s):  
Fish Assemblages ◽  
High Water ◽  
Floodplain Lakes

Rate of digestion in three species of pinnipeds

1984 ◽  
Vol 62 (9) ◽  
pp. 1751-1756 ◽  
Author(s):  
Roger C. Helm
Keyword(s):  
Excretion Rate ◽  
High Water ◽  
High Water Content ◽  
High Metabolic Rate ◽  
Food Passage ◽  
Time Period ◽  
In Captivity ◽  
The Mean ◽  
Clinical Problems ◽  
Approximate Rate

Torpid bowels or an impaction obstruction significantly retards the rate of passage of digesta in an animal and can lead to serious clinical problems. In many captive animals the approximate rate of food passage is well-known, thus allowing for rapid diagnosis and treatment if an intestinal blockage occurs. Although pinnipeds are commonly kept in captivity, the rate of passage of digesta in these animals is not known. In this study, the time period that elapsed before the initial defecation of a dye-marked meal was determined for 20 pinnipeds representing three species. This initial defecation time (IDT) serves as a good indicator of the rate of passage of digesta. The mean IDTs determined for pinnipeds were very fast averaging 5 h or less. No other medium to large carnivore or omnivore has been shown to exhibit such a rapid rate of passage. The extraordinarily fast excretion rate of these animals is even more remarkable considering that their intestine to body length ratios are among the largest in the animal kingdom. It is hypothesized that the rate of passage of digesta in pinnipeds is strongly influenced by their high metabolic rate and the high water content of their digesta.

scholarly journals PRE- and POST-STORM LiDAR SURVEYS FOR ASSESSMENT OF IMPACT ON COASTAL EROSION

2019 ◽  
Vol XLII-3/W8 ◽  
pp. 261-266
Author(s):  
A.-L. Montreuil ◽  
M. Chen ◽  
A. Esquerré ◽  
R. Houthuys ◽  
R. Moelans ◽  
...  
Keyword(s):  
Management Practices ◽  
Morphological Changes ◽  
Storm Surges ◽  
High Water ◽  
Water Levels ◽  
Airborne Lidar ◽  
Coastline Change ◽  
The Mean ◽  
The Impact

<p><strong>Abstract.</strong> Sustainable management of the coastal resources requires a better understanding of the processes that drive coastline change. The coastline is a highly dynamic sea-terrestrial interface. It is affected by forcing factors such as water levels, waves, winds, and the highest and most severe changes occur during storm surges. Extreme storms are drivers responsible for rapid and sometimes dramatic changes of the coastline. The consequences of the impacts from these events entail a broad range of social, economic and natural resource considerations from threats to humans, infrastructure and habitats. This study investigates the impact of a severe storm on coastline response on a sandy multi-barred beach at the Belgian coast. Airborne LiDAR surveys acquired pre- and post-storm covering an area larger than 1 km<sup>2</sup> were analyzed and reproducible monitoring solutions adapted to assess beach morphological changes were applied. Results indicated that the coast retreated by a maximum of 14.7 m where the embryo dunes in front of the fixed dunes were vanished and the foredune undercut. Storm surge and wave attacks were probably the most energetic there. However, the response of the coastline proxies associated with the mean high water line (MHW) and dunetoe (DuneT) was spatially variable. Based on the extracted beach features, good correlations (r>0.73) were found between coastline, berm and inner intertidal bar morphology, while it was weak with the most seaward bars covered in the surveys. This highlights the role of the upper features on the beach to protect the coastline from storm erosion by reducing wave energy. The findings are of critical importance in improving our knowledge and forecasting of coastline response to storms, and also in its translation into management practices.</p>

scholarly journals A newly reconciled data set for identifying sea level rise and variability in Dublin Bay

2021 ◽  
Author(s):  
Amin Shoari Nejad ◽  
Andrew C. Parnell ◽  
Alice Greene ◽  
Peter Thorne ◽  
Brian P. Kelleher ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Tide Gauge ◽  
High Water ◽  
Data Set ◽  
Quality Checks ◽  
Bayesian Linear Regression ◽  
The Mean ◽  
Water Values ◽  
Water Level Measurements

Abstract. We provide an updated sea level dataset for Dublin for the period 1938 to 2016 at yearly resolution. Using a newly collated sea level record for Dublin Port, as well as two nearby tide gauges at Arklow and Howth Harbour, we perform data quality checks and calibration of the Dublin Port record by adjusting the biased high water level measurements that affect the overall calculation of mean sea level (MSL). To correct these MSL values, we use a novel Bayesian linear regression that includes the Mean Low Water values as a predictor in the model. We validate the re-created MSL dataset and show its consistency with other nearby tide gauge datasets. Using our new corrected dataset, we estimate a rate of 1.08 mm/yr sea level rise at Dublin Port between 1953–2016 (95 % CI from 0.62 to 1.55 mm/yr), and a rate of 6.48 mm/yr between 1997–2016 (95 % CI 4.22 to 8.80 mm/yr). Overall sea level rise is in line with expected trends but large multidecadal varaibility has led to higher rates of rise in recent years.

Combining statistical learning and geostatistical approaches in a spatiotemporal framework for low flow estimation

2021 ◽  
Author(s):  
Johannes Laimighofer ◽  
Michael Melcher ◽  
Juraj Parajka ◽  
Gregor Laaha
Keyword(s):  
Statistical Learning ◽  
Mean Squared Error ◽  
Temporal Structure ◽  
Empirical Orthogonal Functions ◽  
Regression Coefficients ◽  
Low Flow ◽  
Support Vector ◽  
Spatiotemporal Model ◽  
Residual Field ◽  
The Mean

&lt;p&gt;&lt;span&gt;This paper aims to develop a spatiotemporal model to estimate monthly low flow quantiles Q95 [P(Q&lt;Q95=0.05)] standardized by catchment area in Austria. Our dataset consists of 325 gauging stations that where consistently monitored between 1976 to 2015, and it covers about 60% of the national territory of Austria. &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;In a first step we are adapting a spatiotemporal model initially designed for modeling air pollution data. This approach is based on empirical orthogonal functions (EOF), that should capture the temporal structure of the spatiotemporal model. The EOFs are weighted by regression coefficients estimated by universal kriging. We extend the model by using GLM-boosting, LASSO, Principal Component Regression (PCR) and Random Forest (RF) for selecting the regression coefficients of the EOFs. Furthermore, we do not limit the kriging structure of the residual field to geographical coordinates but use a broader approach of physiographic kriging. In a second step we implement separate models for the mean parts of the model and the residual parts of the model. The mean field is defined by statistical learning methods as RF, GAM-boosting, LASSO and Support Vector Machines (SVM). For the residual field we define two different approaches, either the &lt;/span&gt;&lt;span&gt;method developed in the first step&lt;/span&gt;&lt;span&gt; or spatiotemporal kriging.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Model performance is evaluated by cross validation and the best model is selected by the mean squared error (MSE). &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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