Geographic distribution of the short-tailed river stingray (Potamotrygon brachyura): assessing habitat loss and fishing as threats to the world’s largest obligate freshwater elasmobranch

2016 ◽  
Vol 67 (10) ◽  
pp. 1463 ◽  
Author(s):  
Luis O. Lucifora ◽  
Santiago A. Barbini ◽  
Sabina Llamazares Vegh ◽  
Pablo A. Scarabotti ◽  
Facundo Vargas ◽  
...  
Keyword(s):  
Water Temperature ◽  
Geographic Distribution ◽  
River Basins ◽  
Paraná River ◽  
Habitat Modification ◽  
Rio De La Plata ◽  
Fishing Pressure ◽  
Río De La Plata ◽  
La Plata ◽  
Parana River

Freshwater elasmobranchs are threatened but little is known about them. Potamotrygon brachyura is the world’s largest obligate freshwater elasmobranch. This makes it popular among fishermen and suggests a susceptibility to anthropogenic threats. We collected records of P. brachyura (n=70) from media, fishermen and scientific sampling, to estimate its global geographic distribution (using both generalised additive and MaxLike models). Then, we estimated the species’ exposure to habitat modification and fishing pressure, by applying multinomial ordinal models with threat levels as response and the presence or absence of P. brachyura as an independent variable. Distance to coast, depth, water temperature range, salinity range and mean water temperature were the main determinants of the distribution in the Río de la Plata. This resulted in a narrow coastal distribution. In the Uruguay and Paraná River basins, the probability of occurrence was positively associated with flow accumulation, percentage of open water and submerged vegetation, and lowland ecoregions, and negatively to wetness index and altitude. This limited the distribution to large lowland rivers. Approximately 41% of the range of P. brachyura in the Río de la Plata was subject to high habitat modification. In the Uruguay and Paraná River basins, this percentage reached 7%; however, the overlap with high fishing pressure was 59%. For conservation purposes, P. brachyura may function as an umbrella species.

scholarly journals Use of otolith strontium : calcium ratio as an indicator of seasonal displacements of the silverside (Odontesthes bonariensis) in a freshwater–marine environment

2013 ◽  
Vol 64 (8) ◽  
pp. 746 ◽  
Author(s):  
E. Avigliano ◽  
A. V. Volpedo
Keyword(s):  
Marine Environment ◽  
Calibration Curve ◽  
Paraná River ◽  
River Delta ◽  
Water Bodies ◽  
Rio De La Plata ◽  
Río De La Plata ◽  
La Plata ◽  
Parana River ◽  
Odontesthes Bonariensis

Strontium : calcium (Sr : Ca) ratios were measured in sagittal otoliths of silverside (Odontesthes bonariensis) from a freshwater–marine environment (Paraná River Delta and Río de la Plata River, South America) in order to understand its seasonal movements. Conductivity was recorded and the water Sr : Ca ratio was determined by inductively coupled plasma–atomic emission spectrometry (ICP-OES). A calibration curve of water Sr : Ca ratio versus otolith Sr : Ca ratio from four isolated lentic water bodies was made to predict silverside displacements in the lower section of the Plata Basin during summer (lotic water bodies). Otolith Sr : Ca ratio of silversides from the Paraná River Delta was associated with the conductivity of water at the locations where the sample was collected. According to this association and the obtained results in the calibration curve, the silversides were displaced from zones where conductivity was 7.45 (mS cm–1), corresponding to the water Sr : Ca ratio in the outer section of the Río de la Plata River (1.92 mmol mol–1). The high values of otolith Sr : Ca ratio found for some fish may indicate that during summer they moved from estuarine waters where salinity increases gradually to the Argentinian Sea.

Heavy metal concentrations in the Lower Paraná River and right margin of the Río de la Plata Estuary

1998 ◽  
Vol 26 (3) ◽  
pp. 963-966
Author(s):  
C. Villar ◽  
M. Tudino ◽  
C. Bonetto ◽  
L. de Cabo ◽  
J. Stripeikis ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Paraná River ◽  
Rio De La Plata ◽  
Río De La Plata ◽  
Metal Concentrations ◽  
Heavy Metal Concentrations ◽  
La Plata ◽  
Parana River

scholarly journals Mollusks (Gastropoda and Bivalvia) of the Multiple-Use Reserve Martín García Island, Río de la Plata River: biodiversity and ecology

2012 ◽  
Vol 72 (1) ◽  
pp. 121-130 ◽  
Author(s):  
II César ◽  
SM Martín ◽  
A Rumi ◽  
M Tassara
Keyword(s):  
Dissolved Oxygen ◽  
Water Temperature ◽  
Environmental Variables ◽  
Sampling Period ◽  
Pomacea Canaliculata ◽  
Rio De La Plata ◽  
Multiple Use ◽  
Río De La Plata ◽  
Oxygen Conductivity ◽  
La Plata

The Island of Martin Garcia is located in the Upper Río de la Plata, to the south of mouth the Uruguay River. The aim of the present study was to analyse the biodiversity of the island freshwater mollusks and their relationships to environmental variables. Twelve sampling sites were selected, five were along the littoral section of the island and seven were Inland ponds. Seven major environmental variables were measured: water and air temperature, percentage of oxygen saturation, dissolved oxygen, electrical conductivity, total dissolved solids and pH. Twenty-seven mollusk species were found, Antillorbis nordestensis, Biomphalaria tenagophila tenagophila , B. t. guaibensis, B. straminea, B. peregrina, Drepanotrema kermatoides, D. cimex, D. depressissimum, Chilina fluminea, C. rushii, C. megastoma, Uncancylus concentricus, Hebetancylus moricandi, Stenophysa marmorata, Heleobia piscium, H. parchappii, Potamolithus agapetus, P. buschii, P. lapidum, Pomacea canaliculata, P. megastoma, Asolene platae, Corbicula fluminea, Eupera platensis, Pisidium sterkianum, P. taraguyense and Limnoperna fortunei. UPGMA clustering of species based on their occurrence in different ecological conditions revealed two main species groups. The Canonical Correspondence Analysis suggests that the species distribution is related to the physico-chemical condition of water. Axis two of the ordination diagram displayed the approximately 95.6% of the correlation between species and environmental variables. Dissolved oxygen, conductivity, water temperature and pH showed the highest fluctuations during the sampling period. The species richness (S) showed relationships mainly with water temperature and conductivity. The biodiversity of the gastropods and bivalves from Martín García Island amounts to up to 26 species. Among the Gastropoda, the Planorbidae family made the most sizeable contribution. The Lithogliphidae P. agapetus (26.28%) and P. buschii (9.50%) showed the highest relative frequencies of occurrence within the littoral environments, while the Planorbidae D. cimex (23.83%) and D. kermatoides (11.59%) likewise did so in the inland ponds.

scholarly journals Biodiversity and ecology of Hirudinea (Annelida) from the Natural Reserve of Isla Martín García, Río de la Plata, Argentina

2009 ◽  
Vol 69 (4) ◽  
pp. 1107-1113 ◽  
Author(s):  
II. César ◽  
SM. Martín ◽  
BS. Gullo ◽  
R. Liberto
Keyword(s):  
Dissolved Oxygen ◽  
Water Temperature ◽  
Environmental Variables ◽  
Rio De La Plata ◽  
Río De La Plata ◽  
La Plata ◽  
Natural Reserve ◽  
Species Groups ◽  
Floating Macrophytes ◽  
Measured Water

The Island of Martin Garcia lies at the confluence of the Uruguay and Paraná Rivers (upper Río de la Plata). This island is an outcrop of the crystalline basement. Due to basalt exploitation the island exhibits several ponds covered by carpets of free-floating macrophytes. Seven major environmental variables were measured: water and air temperature, percentage of oxygen saturation, dissolved oxygen, electrical conductivity, total dissolved solids and pH. Eleven leech species were found, Helobdella striata, H. diploides, H. adiastola and H. hyalina were new records. UPGMA clustering of species based on their occurrence in different ecological conditions revealed three main species groups. Canonical Correspondence Analysis (CCA) explained 97.2% of the correlation between species and environmental variables. H. triserialis shows the widest range of tolerance, H. hyalina shows positive relationships to conductivity; H. diploides shows a high correlation with dissolved oxygen, H. striata, H. lineata, and S. similis are negatively correlated with water temperature, and H. simplex is positively correlated with pH. Relationships between the species richness (S) and the sampling sites were negatively correlated with water temperature and positively correlated with dissolved oxygen. Leech biodiversity from the water bodies of Martín García Island, shows a great diversity of species and a wide plasticity regarding the characteristics of the environmental factors considered.

scholarly journals Annelida (Oligochaeta and Aphanoneura) from the Natural Reserve of Isla Martín García (upper Río de la Plata estuary, Argentina): biodiversity and response to environmental variables

2014 ◽  
Vol 74 (1) ◽  
pp. 128-136 ◽  
Author(s):  
II César
Keyword(s):  
Electrical Conductivity ◽  
Dissolved Oxygen ◽  
Water Temperature ◽  
Environmental Variables ◽  
Sampling Period ◽  
Abundant Species ◽  
Rio De La Plata ◽  
Río De La Plata ◽  
Oxygen Conductivity ◽  
La Plata

The Island of Martín García – located in the Upper Río de la Plata, to the south of the Uruguay River – is an outcropping of the crystalline basement. Fourteen sampling sites were selected, five along the littoral section of the island and nine in inland ponds. Four major environmental variables were measured: water temperature, dissolved oxygen, electrical conductivity, and pH. A total of 34 species of Oligochaeta and Aphanoneura were found, 30 belonging to Naididae plus one species each of the Narapidae, Lumbricidae, Enchytraeidae, and Aeolosomatidae. The thirteen most frequent species were: A. leydigi (30%), N. bonettoi (13%), L. hoffmeisteri (11%), N. variabilis(10%), S. trivandrana (6.5%), A. pigueti (5.6%), D. sawayai (4.5%), D. digitata(3.5%), C. diastrophus (2.7%), A. costatus (2.5%), P. longiseta (2.0%), Enchytraeidae (1.5%), and A. p. paraguayensis(1.4%). UPGMA clustering of species based on their occurrence in different ecological conditions revealed two main species groups. Canonic-correspondence analysis (CCA) was conducted with the 15 most frequent and abundant species in the 9 sampling sites and the 4 environmental variables. Results from the CCA revealed that the order of fluctuation of the environmental variables during the sampling period was, from the greatest to the least: dissolved oxygen, conductivity, pH, and water temperature. Approximately 97.6% of the correlations between species and environmental variables were expressed on axis 1 of the ordination diagram. Species richness correlated with the four environmental variables in the following order, from the weakest to the strongest: water temperature, pH, electrical conductivity, and dissolved oxygen.

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