André Luiz Henríques Esguícero

The fish fauna in the fish passage at the Ourinhos Dam, Paranapanema River

The composition and abundance of the fish assemblage were evaluated in the fish ladder of Ourinhos Dam, the newest dam (closed in 2005) in the cascade of dams constructed on the Paranapanema River. Samplings were carried out three times on a diel cycle, in three sampling periods, two in the warm season and one in the cold season of 2008 - 2009. The ladder was closed and emptied and the entire fish assemblage was sampled and identified. Most individuals were released alive downstream of the dam. The assemblage found in the ladder was compared with the fish fauna sampled in the reservoir and in downstream sites, in the same period. Twenty seven species and a total of 4682 individuals were caught in the ladder. Pimelodus maculatus was the only migratory species, which was caught in low number in the ladder (0.04% of the total captured), where small sedentary species predominated. The most abundant species were the non-migratory Apareiodon affinis, Bryconamericus stramineus, Astyanax fasciatus and Parodon nasus. Individuals observed in the ladders window were moving up- and down the passage. The fish ladder is a microhabitat inhabited by an abundant association of benthic organisms that is probably used as a food resource for the fish assemblage in the ladder. The similarity between the fish fauna in the ladder and that of the Ourinhos Reservoir was low (26%). The species richness of migrants in the stretch between the uspstream reservoir (Chavantes) and the downstream one (Salto Grande), before the Ourinhos dam closure (23 species) was reduced to 16 and 12 species in Salto Grande and Ourinhos reservoirs, respectively, after the dam closure, and to a single species in the ladder.

Diet and ecomorphology of Leporinus reticulatus (Characiformes: Anostomidae) from the upper Rio Juruena, MT, Brazil: ontogenetic shifts related to the feeding ecology

The conservation of diverse and well-distributed fish taxa, as the genus Leporinus, relies intrinsically on the knowledge of the ecological attributes of its representatives. Aiming to increase this knowledge, studies on diet and ecomorphology are ideal to provide important information about species ecology. Thus, this study aimed to analyze aspects of feeding ecology of L. reticulatus, from the upper Rio Juruena, Mato Grosso State, Brazil. The diet of specimens in different ontogenetic stages was compared, as well as their teeth morphology and ecomorphological attributes. Leporinus reticulatus presented omnivorous diet, with higher consumption of invertebrates by smaller specimens (younger ones), and gradual introduction of plant items in larger specimens (older ones). The items consumed by the individuals and the ecomorphological attributes indicated that the species is generalist and opportunistic, besides its association with the river bottom, evidencing a benthic feeding behavior. This species presents a gradual ontogenetic modification in teeth shape and mouth positioning, ranging from a terminal mouth with tricuspid teeth, in smaller specimens, to an inferior mouth with spatula shaped teeth with no cusps, in larger specimens.The ecomorphological attributes indicate an increasing swimming efficiency, and ability for performing vertical displacements, along the ontogenetic development, which in addition to the morphological ontogenetic alterations in the buccal apparatus, contributes to a better ability to explore another niches.

A new sexually dichromatic miniature Hyphessobrycon (Teleostei: Characiformes: Characidae) from the Rio Formiga, upper Rio Juruena basin, Mato Grosso, Brazil, with a review of sexual dichromatism in Characiformes

Hyphessobrycon myrmex sp. nov., is described from the Rio Formiga, upper Rio Juruena, upper Rio Tapajós basin, Mato Grosso, Brazil. The new species can be distinguished from congeners by having the lower half of the body deeply pigmented with dark chromatophores, chromatophores concentrated above the anal fin and forming a broad, diffuse, dark midlateral stripe and by having a dense concentration of dark chromatophores along unbranched dorsal-fin rays and distal portions of the two or three subsequent branched rays. In life, H. myrmex exhibits a conspicuous sexual dichromatism, with adult males red to orange and females and immatures pale yellow. A list containing 108 sexually dichromatic taxa in six families of Characiformes is provided and the distribution of this poorly known type of dimorphism across the Characiformes is discussed.

New records of fishes (Actinopterygii: Ostariophysi) from the Upper Tapajós River Basin

The first report of Sartor (Anostomidae) and Tatia intermedia (Auchenipteridae) for the Upper Tapajos River Basin are presented here. Sartor is very rare on collections, and is reported only from the Trombetas, Tocantins and Upper Xingu river basins. Tatia intermedia is registered in the upper reaches of the Araguaia, Tocantins, Xingu, and Capim rivers, tributaries of the lower Amazon River in Brazil, northwards to the Suriname coastal rivers and the Essequibo River in Guyana.

Fish diversity in the cascade of reservoirs along the Paranapanema River, southeast Brazil

The Paranapanema River is a major tributary of the upper Paraná river basin. Eleven hydropower dams regulate its main course, but no study has investigated fish diversity in these impoundments at the basin-scale. The present study investigated spatial patterns of richness, composition, and abundance of native (non-migratory and migratory) and non-native fishes in the cascade of reservoirs along the Paranapanema River. The study is based on data collected from 34 independent studies conducted in nine reservoirs (47 samples). The compilation recorded 161 species, being 111 native (14 migratory) and 50 non-native. Total richness ranged between 56 and 112 species/reservoir, with a mean of 72 (49.9 non-migratory, 8.1 migratory and 14 non-native). The number of non-migratory species showed no spatial trend along the cascade system, but migratory and non-native richness increased toward downstream reaches. We also observed spatial variation in species composition along the cascade system, but some non-native fishes were widely distributed. Migratory fishes showed low relative abundance (usually < 10%), while non-native species were common and more abundant, especially in reservoirs downstream. Our results revealed a high diversity of fishes in the cascade of impoundments, but indicated that migratory fishes are rare, while non-native species are common or dominant.(AU)