The effects of a dam closure (Porto Primavera Dam) on reproduction the main species that use floodplain located below nursery area were determined. Specifically, we examined, before and after dam, spatial distribution larvae differences in density according to life strategy (migratory non-migratory species). Fifteen points distributed along channels Paraná, Ivinheima Paranapanema rivers sampled, between 1997 2001, (October December 1998—pre; January 1999 March 2001—post closure), during...

The purpose of this study was to evaluate the role abiotic factors on fish larvae occurrence. Samplings were carried out monthly at 12 stations (grouped in four areas) Amambaí, Ivaí and Paraná rivers Itaipu Reservoir (upper River basin), from October 1994 January 1995 (spawning season). Simultaneously, we obtained water temperature, pH, electrical conductivity, dissolved oxygen, level, velocity, rainfall. Principal Component Analyses (PCA) Detrended Correspondence (DCA) applied summarize...

ABSTRACT The unique environmental characteristics of the tropics and subtropics, including precipitation patterns, photoperiods temperatures, can influence riverine zooplankton communities in contrasting ways. Therefore, we aimed to investigate seasonal dynamics tropical subtropical rivers compare structure response distinct climatic conditions. To this end, collected samples from located two different zones Brazil (tropical subtropical) during winter, spring, summer autumn. Our results...

Studies on the occurrence, temporal distribution and nychthemeral variation of Macrobrachium amazonicum (Heller, 1862) were undertaken in Leopoldo's Inlet, upper Paraná River, Porto Rico, Paraná, Brazil. Seventeen thousand sixty specimens (11,786 larvae 5,274 juveniles) captured with a conicalcylindrical plankton net mesh 0.5mm monthly samples between February 1991 1992. Results show that greatest densities (301.83 larvae/10m³) juveniles (168.8/10m³) this species caught December 1991....

Studies on fish assemblages in streams point out, that understanding the relationship between species and their environment is crucial for conservation. The present study aimed at evaluating effects of changes abiotic variables composition structure Neotropical urban from southern Brazil with different levels urbanization. showed significant differences along urbanization gradient observed streams. Tolerant non-native were found more urbanized sites. A matrix correlation revealed a spatial...

The spatial and temporal distribution nychthemeral variation of fish larvae in six stations (Ivinhema, Patos, Paraná, Cortado, Baía Guaraná) the floodplain high Paraná river are provided. paper also provides relationship this to some environmental factors. From March 1992 February 1993 ichthyoplanktonic samples were collected by conic cylindrical nets, with 0.5mm mesh size fluxometer attached, 10-minute hauls at surface bottom during cycles. At same time water taken determine During above...

Abstract This paper purposed to evaluate alterations in fish assemblage (structure and species richness) variations the abundance of most abundant captured Piquiri River, due closure Porto Primavera (in 1998; located upstream River mouth) Itaipu 1982; downstream) dams upper Paraná River. The effects selected environmental variables were also determined. Fishes sampled during four distinct periods. Six samplings conducted each period, at two different sites (Campina Apertado). For sampling,...

Abstract Zooplankton are widely recognised as being regulated primarily by predators and food availability. In reservoirs, the quantity quality of resources generally affected characteristics water, which in turn controlled flow pulse generated operation dams. this study, we investigated relationship between zooplankton, water availability (phytoplankton) eight hydroelectric reservoirs located Brazil. Samples were collected during rainy dry periods 2008 2009. general, exhibited mesotrophic...

The aim of this work was to study the occurrence ichthyoplankton in a region affected by water regulation dams. area located Ilha Grande National Park, upper Paraná River floodplain. Specifically, we examined temporal and spatial distribution Ichthyoplankton, identified spawning areas established relationships between abundances fish eggs larvae some limnological hydrological variables. Samples were taken monthly October March from 2001 2005 at 24 sampling sites. For analytical purposes,...

The objective of this study was to assess the abundance, attributes assemblages, and spatial temporal distributions fish larvae their relationships with some abiotic variables in two floodplain lakes different degrees connection Paraná River Ilha Grande National Park, PR, Brazil. Four sampling sites were chosen, each lake. Night samples taken plankton nets during three spawning seasons (monthly, from October March) 2001 2005. highest diversity abundance recorded at Saraiva Lake, 25 taxa...

This study focused on intra and interspecific variations in the diet of small species Pelotas River, upper Uruguay River ecoregion. We tested hypothesis that five characids coexist via resource partitioning. Samplings were performed quarterly between August 2013 May 2014 at 14 sites basin, using gillnets different mesh sizes, seines, cast nets electrofishing. In this study, contents 1,253 stomachs analysed from Astyanax dissensus , A. paris saguazu xiru Bryconamericus patriciae . The main...

In reservoirs, zooplankton strongly interact with the physical and chemical characteristics of water, this interaction is mainly influenced by climate variation different methods used to manage dam water level. Therefore, aim study was evaluate how distinct operating modes two cascade reservoirs affected richness, abundance, composition zooplankton, both spatially (intra inter-reservoirs) temporally (annual seasonal). study, upstream reservoir (Salto Santiago) operates using storage method,...

Larvae feeding selectivity of Iheringichthys labrosus , Hypophthalmus edentatus and Plagioscion squamosissimus was assessed, examining the role mouth gape in prey selection. Fish larvae were sampled Itaipu Reservoir (Brazil–Paraguay). H. larvae, with small similar sizes, exhibited slightly different diets; I. preferred cladocerans ( Bosmina hagmanni huauriensis Bosminopsis deitersi ) rotifer Brachionus calyciflorus . however, primarily ingested B. Ceriodaphnia cornuta Daphnia gessneri...

Abstract Aim: This study aimed to characterize the zooplankton structure in highland streams southern Brazil, Pelotas River sub-basin, as well respective relationships with environmental conditions different seasons. Methods Zooplankton was collected using a plankton net (68 µm mesh) and concentrated into volume of 50 ml for later analysis laboratory. Sampling occurred during winter (August 2013), spring (November summer (February 2014) autumn (May 2014). Results Rotifers testate amoebae...

Large reservoirs usually present spatial gradients in fish assemblage, distinguishing three strata (littoral, pelagic, and bathypelagic) along the vertical horizontal axes, zones (fluvial, transitional, lacustrine) longitudinal axis. The main objective of this study was to assess if small also assemblage attributes structure as already observed large reservoirs. Fish surveys were conducted quarterly, from 2003 2008, Mourão Reservoir (Mourão River, Paraná, Brazil), using gillnets with...

Abstract River damming and associated reservoir causes intense dramatic changes that create new environments, with particular structure functioning. In these systems, flow control artificial variations in water level are important determinants of the fish assemblages. Planned reduction (drawdown) is used to manage productivity reservoirs. However, effects non‐planned reductions, such as those related collapse spillway gates, rarely studied. The objective this study was evaluate a rapid...

Spatial and temporal distribution of larvae juveniles trahira, Hoplias aff. malabaricus (Erythrinidae), their relationship with environmental parameters in the Upper Paraná River floodplain were analyzed. Sampling H. has been conducted during period from November 1991 through February 1995, 42 sampling stations distributed four sub-areas: Ivinhema I, II, Baía, Paraná. During same period, data obtained for water temperature, dissolved oxygen, pH, electrical conductivity, river level,...