Color patterns of the body are commonly used to distinguish and identify species of Trichomycterus. Therefore, variation in color pattern in a population can cause doubt concerning species identification. With the purpose to test the hypothesis of high variation in color pattern of Trichomycterus davisi (Haseman, 1911), 118 specimens were collected in a stream of a private Ecological Park in southern Brazil, of which 88 were used in the morphological analysis and 30 for DNA barcoding analysis. Three phenotypic classes were determined analyzing the distribution, size and shape of dark brown spots and blotches. The results of morphometric analysis indicate a tendency of association of those pigmentation patterns with the standard length, evidencing ontogenetic variation of color pattern in the species. The results of K2P intraspecific genetic distance (<0.72%), haplotypes network and Bayesian phylogenetic tree corroborate the existence of only one species with a high variable color pattern.

Fishes were collected at 36 sites in first order streams of Tibagi River basin, Paraná state, Brazil. A total of 2,669 individuals belonging to 47 species of 13 families and six orders were collected. The number of collected species represented 95.9% of the expected number of species for the studied area as estimated by Chao 1, and 93.4% by ACE, indicating an effective sampling. The highest richness was recorded in the tributaries at the lower region (Zone III) of the Tibagi River basin, with 33 species, including 16 species not found in the other regions of the basin. In the streams of the middle and upper regions (Zones II and I) each presented less richness, with 10 (two exclusive) and 25 (11 exclusive) species, respectively. This study shows a high geographic variation in the composition of fish fauna among zones, maybe related to historical and/or ecological influences.

ABSTRACT. Most studies of diversity and genetic structure in neotropical fish have focused on commercial species from large rivers or their reservoirs. However, smaller tributaries have been identified as an important alternative migratory route, with independent pools of genetic diversity. In this context, the present study aimed to evaluate genetic diversity and structure in five neotropical fish species from a region of Laranjinha River in the upper Paraná River basin. PCR-RAPD (random amplified polymorphic DNA) markers were used to characterize around 40 individuals of each species distributed upstream and downstream of Corredeira Dam that interrupts the river. The descriptive index of genetic diversity (P = 30.5-82%; H E 0.122-0.312) showed that the populations have acceptable levels of genetic diversity. The values for Nei's genetic distance (D N min 0.0110 and max 0.0306) as well as the genetic structure index and the analysis of molecular variance (AMOVA, ϕ ST min 0.0132 and max 0.0385) demonstrated low, but significant levels of genetic structure. Bayesian analysis of assignment found two k clusters, including several individuals with mixed ancestry for all populations from the five species analyzed. These findings along with historical data on rainfall and the low dimensions of the dam studied here support the hypothesis that periodic floods enable the transit of individuals between different localities mitigating the differentiation process between populations.

This work is the most comprehensive survey of the Laranjinha River´s fishes, a tributary of the Cinzas River, Paranapanema River basin. Throughout its course, there is only a low-height dam, including a transposition system located 98 km from its mouth. The sampling was carried out in nine locations, from the source to the mouth, with six field incursions in each location, using different fishing gear. A total of 11,924 fish were collected, distributed in seven orders, 27 families, and 100 species. The most representative order in the number of species was Siluriformes, followed by Characiformes. As for the families, Loricariidae comprised 21% and Characidae 14% of species richness. Phalloceros harpagos was the species with the highest absolute abundance, representing 11.3% of the total, followed by Hypostomus ancistroides with 9.8%. However, considering the average abundance and frequency of occurrence, Hypostomus ancistroides was the most abundant species, followed by Hypostomus cf. paulinus, Psalidodon aff. paranae and Phalloceros harpagos. Among the collected species, the Apteronotus acidops, Brycon orbygnianus, Brycon nattereri, Crenicichla jupiaensis, and Rhinelepis aspera were classified as endangered on the most recent IUCN Red List. Also, from the total sampled fish, 9.8% are considered non-native species. Among the native species recorded, 10 species are large migratory species, which indicates that the Laranjinha River is a route for spawning and maintenance of species diversity in the middle Paranapanema River. Therefore, the Laranjinha River is a heritage of fish diversity and deserves special attention in its preservation.

ABSTRACT When a river is dammed, impacts differ according to distance from the dam under consideration, and sites closer to the dam are more affected than distant ones. Damming a river changes the flow and landscape characteristics, which, in turn, change the hydrological, limnological and ecological dynamics, such as biological production, species distribution, and ecosystem structuring, functioning and services. This study evaluates the distribution pattern of the Siluriformes (catfish) fish species near a small hydroelectric power plant in the Jaguariaíva River, considering three distinct distances from the dam: upstream region, reservoir and downstream region. Samples were taken with gillnets between March 2013 and December 2014. The abundance and richness of the Siluriformes species were evaluated. A permutational multivariate analysis of variance was used to access possible differences in species composition among sites. Finally, a permutational analysis of multivariate dispersion was used to assess possible differences among sampling sites and to examine composition similarities among sites. A total of 840 Siluriformes individuals were captured, distributed among ten species and four families. The highest richness was observed in the downstream region, while the lowest richness was observed in the reservoir area. Differences in the abundance of species were observed between the three distinct regions; the downstream region presented the highest species abundance (CPUE), whereas the lowest abundance was observed in the dam region. Hypostomus paulinus and Hypostomus strigaticeps were abundant species, but exclusively sampled in the downstream region, while Corydoras ehrhardti and Cambeva diabola presented their highest abundance in the upstream region. The distinct longitudinal distribution of Siluriformes observed in this study can be interpreted as indicative of the negative effects of damming. Our study suggests that building small dams may result in negative impacts on the fish assemblage, impacts comparable to those of large reservoirs in terms of spatial changes. It is fundamentally necessary to better evaluate the environmental impacts of small dams in the Neotropical region, especially because few is known about them and how such impacts are comparable to impacts of larger reservoirs.

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In the Neotropics, freshwater streams harbour high fish diversity and are constantly threatened by anthropogenic disturbance. However, there are few studies on the genetic diversity of fish populations inhabiting these streams. We aimed to assess, based on microsatellite and mitochondrial DNA markers, the population structure and genetic diversity of the suckermouth catfish, Hypostomus ancistroides, a Neotropical species widely distributed across the Upper Paraná River Basin in South America. Twenty-five locations were sampled, distributed across 18 sites in six tributary streams and another seven sites in the main river channel. Our analyses revealed a spatial heterogeneity in genetic diversity within the basin, indicating fine-scale genetic structuring. Samples from all streams showed exclusive haplotypes and private alleles, reinforcing the importance of preserving the tributaries for the conservation of the genetic diversity of the studied populations. The fine-scale genetic structuring of H. ancistroides is probably related to the limited displacement capacity of this species.