Fish, Passa Cinco stream, Corumbatai River basin, state of São Paulo, Brazil.

The fishes of the present study were collected in Passa Cinco stream, a main river of Corumbatai river basin, Tiete drainage. Five sites were selected in that stream, downstream from headwater to its mouth, and six samplings were performed using the following fishery equipment: a sieve, electric fishery equipment, gill nets and fish-traps. 5082 individuals, 62 species, 18 families and 6 orders were captured. The orders Characiformes and Siluriformes were the most representative and the families Characidae and Loricariidae presented the largest in number of species.

River avulsions on the Taquari megafan, Pantanal wetland, Brazil

The Pantanal wetland is located in a tectonically active interior sedimentary basin in west-central Brazil. The south-flowing Paraguay River is the trunk-river of an alluvial constructional landform comprising several large alluvial fans, the largest one of which is the Taquari megafan. The Taquari River flows in two distinct geomorphologic zones within the megafan. Entrenched on sediments of Pleistocene fan lobes, the Taquari River flows in a 3 to 5 km wide meander belt in the upper fan, where avulsion is hindered by entrenchment. Downstream of the intersection point, stream discharge progressively decreases and the Taquari River becomes narrow and shallow toward the Paraguay River plain. Within the distributary fan lobe, the channel-levee sandy complex is topographically higher than the adjacent floodplains and avulsion is a natural consequence of crevasses in the natural levees. Many channel avulsions have occurred during the last decades and documented cases show that significant channel changes may take place in a few years. Beginning with crevassing in 1988 and ending with the abandonment of the former channel in 1998, the river completely changed course in the lower fan. Presently, a major avulsion is occurring in the upper portion of the growing fan lobe, where many crevasses have appeared in the natural levees with associated splays onto the floodbasin. New anastomosed channels have formed north of the Taquari River, but downstream of them the flow is unconfined and the water spreads into natural floodbasins. This avulsion is still in process and allows observation of channel evolution, the geomorphic features produced, the sedimentary processes involved, and resulting effects. If the new channels do not rejoin the main channel, the river mouth may abandon its present master channel and shift to a position a hundred kilometers north from its present position. A large volume of sediment has been transferred to the floodbasin, with progradation of crevasse splay deposits over fine overbank sediments. Many geomorphic features, recognizable in satellite and radar images, clearly show that avulsion has occurred many limes before in the Taquari River. Avulsion belt deposits and former diverted channels testify to ancient avulsion events within the fan lobe and show that progradation of splays onto the floodbasin is the most important infilling process within the Taquari distributary fan lobe. The avulsion process in the lower Taquari River has accelerated in the last 30 years, along with the magnitude of flooding. Pasture and intensive agriculture in the catchment area has increased the sediment supply to the wetland, but larger floods are also a consequence of higher rainfall since 1973. Avulsion and floods have been a cause of great concern among the local population and landowners. Before human intervention in attempting to control floods, however, a better understanding of the avulsive river system is needed, especially because a major navigation project including the channelization of the Paraguay River was recently proposed. (c) 2005 Elsevier B.V. All rights reserved.

Lacustrine records of Holocene flood pulse dynamics in the Upper Paraguay River watershed (Pantanal wetlands, Brazil)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Contrasting fluvial styles of the Paraguay River in the northwestern border of the Pantanal wetland, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mercury in Amazonian fish from Madeira River basin, Rondonia state, Brazil

This investigation was carried out at the Madeira River basin, located in the state of Rondonia, Brazilian Amazon. Fish from Madeira, Jaciparana, and Jamari rivers between 7 and 11 degrees parallels south and between 62 and 65 degrees meridians west in Rondonia state, Brazil, were sampled and chemically analyzed for mercury in order to evaluate if the inputs of this metal into the food-chain is occurring in levels reaching values above those recommended by the World Health Organization. This is because such an element is very dangerous when ingested by humans and its presence was extensively identified some years ago in the area, since it was utilized as an amalgam in processes for recovering alluvial gold.

Sedimentation rates in Atibaia River basin, São Paulo State, Brazil, using Pb-210 as geochronometer

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Hydrochemistry and weathering rates on Corumbatai River basin, São Paulo State, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Pb-210 and composition data of near-surface sediments and interstitial waters evidencing anthropogenic inputs in Amazon River mouth, Macapa, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The fate of copepod populations in the Paranapanema River (São Paulo, Brazil), downstream from the Jurumirim dam

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Photosynthetic rate of the aquatic macrophyte Egeria densa Planch. (Hydrocharitaceae) in two rivers from the Itanhaém River Basin in São Paulo State, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The invertebrate colonization during decomposition of Eichhornia azurea kunth in a lateral lake in the mouth zone of Paranapanema River into Jurumirim Reservoir (São Paulo, Brazil)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Carbon sources and trophic position of the main species of fishes of Baía River, Paraná River floodplain, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Age, growth and yield per recruit analysis of the pintado Pseudoplatystoma corruscans (Agassiz, 1829) in the Cuiabá River basin, Pantanal Matogrossense, Brazil

A idade e o crescimento do pintado Pseudoplatystoma corruscans foram estudados durante o período de maio de 1994 a maio de 1995. O comprimento-padrão variou de 52 a 145 cm e o peso total, de 1,3 a 41 kg. As relações biométricas entre comprimento-padrão (Ls) e comprimento total (Ltotal) e entre peso total (Wt) e comprimento-padrão (Ls) foram obtidas, sendo, respectivamente: Ltotal = 3,296 + 1,069 * Ls e Wt = 0,00624 * Ls3,134. O fator de condição, calculado mensalmente, sugere que a desova ocorreu entre os meses de fevereiro e março. A idade foi estimada pela contagem de anéis de crescimento presentes nos raios modificados (esporão) das nadadeiras peitorais, detectando 10 classes etárias. A distância média do último anel até a borda do esporão sugere que o período de menor crescimento ocorreu entre julho e setembro (seca). A equação de von Bertalaffy que descreve o crescimento do pintado é: Lt = 183 * [1 - exp - 0,085 * (t + 3,274)]. A mortalidade total obtida foi Z = 0,24 ano-1 e a mortalidade natural M = 0,20 ano-1. Com o presente nível de explotação, F = Z - M = 0,04 ano-1, conclui-se que o estoque do pintado ainda não estava sobrexplotado na bacia do rio Cuiabá, Pantanal Matogrossense, na época em que foi realizado o estudo.

Ichthyofauna of two streams (silted and reference) in the Upper Paraná river basin, Southeastern Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)