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Paraná River (paraná + river)

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Earth and Environmental Science55%

Terms modified by Paraná River

  • paraná river floodplain
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    Selected Abstracts

    Veligers of an introduced bivalve, Limnoperna fortunei, are a new food resource that enhances growth of larval fish in the Paraná River (South America)

    FRESHWATER BIOLOGY, Issue 9 2010
    ESTEBAN M. PAOLUCCI
    Summary 1.,Larvae of ,sábalo', Prochilodus lineatus, whose adults represent over 60% of overall fish biomass in the Río de la Plata Catchment, have been observed to feed intensively on veligers of the exotic bivalve Limnoperna fortunei. 2.,To assess the effects of this dietary shift on the growth of P. lineatus, 28-day laboratory experiments were carried out feeding newly hatched P. lineatus larvae with three diets: zooplankton artificially enriched with L. fortunei veligers; natural zooplankton; and zooplankton artificially enriched with cladocerans and copepods. The average length, weight and gut contents of the fish larvae were assessed weekly and metabolic rates of fish larvae were measured. 3.,Proportions of veligers in gut contents were always higher than those in the experimental diet: 100, 76 and 21% for veliger-enriched, natural and low-veliger diets, respectively. Larvae fed a veliger-enriched diet grew to a significantly larger size than larvae fed the other two diets. In energetic balance comparisons using metabolic rates and prey energy content, all three diets were sufficient to support metabolism and growth. The greatest values of excess energy at the end of each week were in the veliger-enriched experiments. 4.,Feeding on veligers of L. fortunei significantly enhances the growth of P. lineatus larvae and supports the idea that this new and abundant resource is selectively preyed upon by P. lineatus during its larval stage. Higher growth rates may stem from the higher energy contents of veligers compared to crustaceans and/or from the lower energy costs of capturing slower prey. [source]

    A review of the suspended sediment budget at the confluence of the Paraná and Paraguay Rivers

    HYDROLOGICAL PROCESSES, Issue 22 2009
    Mario L. Amsler
    Abstract In this paper, the sediment budget at the confluence of the Paraná,Paraguay Rivers is updated on the basis of new suspended sediment concentration data, obtained during the 1990s at carefully located cross-sections, after the construction of several large reservoirs. With these data, it was possible to estimate that the suspended sediment load transported by the Upper Paraná River had decreased by 60% due to the influence of the dams. This decrease occurred in spite of the influence of climate change across the Upper Paraná and Paraguay basin, which increased the precipitation and surface runoff. As a consequence of these anthropogenic and natural processes, the Bermejo River (the main source of wash load to the system) accounts for an increasing proportion of the sediment transport along the middle and lower reaches of the Paraná River. The Paraná River currently transports about 120 × 106 t year,1 of wash load, with nearly 90% of this being supplied by the Bermejo. The contribution from the Bermejo is now about 35% larger than its contribution during the 1970s, when it accounted for approximately 60% of the sediment load of the Paraná River. These changes that have occurred over the last 30 years have enhanced the natural asymmetrical distribution of solid and water discharges in the Paraná River basin. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    The geochemical characteristics of the Paraná River suspended sediment load: an initial assessment

    HYDROLOGICAL PROCESSES, Issue 7 2003
    Pedro J. Depetris
    Abstract Most water in the Paraná River drainage basin is supplied by the tropical Upper Paraná (over 60% of the total annual water discharge, 550 km3). The total suspended solids (TSS) load (c. 80 × 106 t year,1), however, is essentially furnished (50,70%) by the mountainous, arid and mostly sediment-mantled upper Bermejo River drainage basin. This characteristic suggests that the Paraná River solid load (TSS, 600 km upstream from the mouth) is largely recycled sedimentary material, whose discharge-weighted mean chemical index of alteration is c. 71. The extended UCC-normalized multi-elemental diagrams are similar to those of other world rivers. Nevertheless, the detailed inspection of UCC-normalized rare earth element (REE) ,spidergrams' reveals a lithological source for the Paraná River TSS that might be compatible with either tholeiitic flood basalts (widespread in the upper drainage) or with young Andean intermediate volcanic rocks. In view of the Bermejo River's dominant role as a sediment contributor, we feel that the signature preserved in the Paraná's TSS is the latter. Conversely, the Uruguay River TSS REE signature is certainly determined by the extensive weathering products of Jurassic,Cretaceous tholeiitic basalts. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Migratory movements of pacu, Piaractus mesopotamicus, in the highly impounded Paraná River

    JOURNAL OF APPLIED ICHTHYOLOGY, Issue 6 2007
    M. C. Makrakis
    Summary A mark-recapture study was conducted in 1997,2005 to investigate movements of stocked pacu, Piaractus mesopotamicus, in the Paraná River Basin of Brazil, Paraguay, and Argentina. Fish raised in cages within the Itaipu Reservoir and in ponds were tagged externally (n = 2976) and released in the Itaipu Reservoir (53.2%) and bays of its major tributaries (46.8%). In total, 367 fish (12.3%) were recaptured. In all, 91% of the pacu moved away from the release site; upstream movements were more extensive than downstream movements. Pacu traveled upstream a maximum of 422 km (average of 41.3 km) at a maximum rate of 26.4 km day,1 (av. 0.8). Downstream movements were limited in terms of number of individuals and distance moved. Fish released during the wet season moved farther than those released during the dry season, and feeding rather than spawning might have been the compelling reason for movement. Although fish passed downstream through dams, none of the marked fish were detected to have moved upstream through the passage facilities. Pacu showed movement patterns not radically different from those of other neotropical migratory species, but their migratory movements may not be as extensive as those of other large migratory species in the basin. [source]

    Intrapopulational polymorphism of nucleolus organizer regions in Serrapinnus notomelas (Characidae, Cheirodontinae) from the Paraná River

    JOURNAL OF FISH BIOLOGY, Issue 5 2008
    A. P. Santi-Rampazzo
    Analysis of the nucleolus organizer regions by silver nitrate (AgNOR), fluorescent in situ hybridization (FISH) and C-banding of Serrapinnus notomelas from the Paraná River, PR, Brazil revealed intrapopulational polymorphisms that could be classified into six patterns (I,VI). Pattern I consisted of a single nucleolus organizer region (NOR) on chromosome pair 26 with at least one active homologue, indicating that it was a preferential NO. This NOR was also present in all the other patterns. In addition, seven other variable pairs appeared in patterns II,VI. These polymorphisms may indicate transpositions of rDNA genes, located on pair 26, to various sites in the genome. These transpositions may be due to transpose mechanisms or reinsertion into sites that have sequences homologous with the inserts. C-band analysis also reflected this variability and confirmed the various patterns described here. [source]

    Variability in the carbon isotope signature of Prochilodus lineatus (Prochilodontidae, Characiformes) a bottom-feeding fish of the Neotropical region

    JOURNAL OF FISH BIOLOGY, Issue 6 2007
    C. A. Lopes
    The spatial and seasonal variability of stable carbon isotopes in detritivorous Prochilodus lineatus, primary producers and particulate organic carbon (POC) were examined to promote a better understanding of the trophic dynamics of food webs in Neotropical ecosystems. Spatial variability in carbon isotope composition in the species showed a decreasing gradient in the Upper Paraná River system, from the Paraná River and Itaipu Reservoir subsystems to the Baía and Ivinheima subsystems. Fish ,13C followed the isotopic trend of POC along the Paraná River and Baía subsystem. Seasonal differences were not observed in fish. The analysis of percentile contribution of C3 and C4 sources in the species diet revealed the predominance of C3 plants (phytoplanktonic and periphytic algae and riparian vegetation) in most of the analysed subsystems and seasons. Nevertheless, the considerable participation of riparian vegetation was verified, especially in the Ivinheima subsystem in the dry season. C4 macrophytes presented a maximum contribution along the Upper Paraná River. These results demonstrate the existence of specific variability for the consumer and their food sources in different environments of the same ecosystem. [source]