The physicochemical variables and the ichthyofauna associated with aquatic macrophyte beds in two stretches of the baı´a Caiçara were evaluated seasonally between September 2005 and May 2007. Low depth, high water transparency, and relatively well-oxygenated waters characterized both stretches during the low water season, whereas the flooding of the upper Paraguay River correlated with drastic alterations in these variables: depth registered a fivefold increase, and turbid and anoxic waters predominated during the high water season. During the falling and low water seasons, species richness, fish abundance, biomass, and diversity were significantly higher than during periods of rising and high waters. The presence of large-sized migratory species, however, was strictly associated with the high water season. The results suggest strong relationships between the abiotic and biotic components of the system and indicate an overall high degree of dependence of the system on the hydrological seasonality of the upper Paraguay River.

Non-native fish (NNF) can threaten megadiverse aquatic ecosystems throughout the planet, but limited information is available for the Amazon Region. In this study we review NNF data in the Amazonian macroregion using spatiotemporal records on the occurrence and the richness of NNF from a collaborative network of 35 regional experts, establishing the Amazon NNF database (ANNF). The NNF species richness was analyzed by river basin and by country, as well as the policies for each geopolitical division for the Amazon. The analysis included six countries (Brazil, Peru, Bolivia, Ecuador, Venezuela, and Colombia), together comprising more than 80% of the Amazon Region. A total of 1314 NNF occurrence records were gathered. The first record of NNF in this region was in 1939 and there has been a marked increase in the last 20 years (2000–2020), during which 75% of the records were observed. The highest number of localities with NNF occurrence records was observed for Colombia, followed by Brazil and Bolivia. The NNF records include 9 orders, 17 families and 41 species. Most of the NNF species are also used in aquaculture (12 species) and in the aquarium trade (12 species). The most frequent NNF detected were Arapaima gigas, Poecilia reticulata and Oreochromis niloticus. The current data highlight that there are few documented cases on NNF in the Amazon, their negative impacts and management strategies adopted. The occurrence of NNF in the Amazon Region represents a threat to native biodiversity that has been increasing “silently” due to the difficulties of large-scale sampling and low number of NNF species reported when compared to other South American regions. The adoption of effective management measures by decision-makers is urgently needed and their enforcement needed to change this alarming trend and help protect the Amazon’s native fish diversity.

The Aripuanã River basin is part of one of the most biodiverse hydrographic basins on the planet; however, the lack of information on fish diversity in the basin is notable, particularly upstream to the Dardanelos and Andorinhas waterfalls complex. For this study, we sampled 50 m stretches of 71 streams in the Aripuanã River basin, upstream and downstream of the Dardanelos and Andorinhas waterfalls complex. Sampling occurred in the drought period in 2013 and 2014. A total of 11,334 specimens were capture, belonging to five orders, 21 families and 80 species. Among the 80 species, 71 were caught in the downstream and 45 in the upstream region. Overall, there were 36 species in both upstream and downstream samples, 35 exclusive to the downstream segment, and nine were restricted to the upstream region. Despite the low levels of current knowledge, at least 15 endemic fish species could be present in the Aripuanã River basin, and four from these 15 species were sampled in this study. Dardanelos and Andorinhas waterfalls complex are important barriers and we found significant differences in fish assemblage between upstream and downstream regions.

Astyanax paranae Eigenmann, 1914 é um pequeno caracídeo conhecido como lambari-do-rabo-vermelho, ocorrendo em vários rios das sub-bacias do alto rio Paraná. Tendo em vista que as características ambientais como disponibilidade de recursos, diversidade de habitats entre outras podem selecionar atributos específicos possibilitando diferenciações morfológicas, testamos a hipótese de que ambientes diferentes podem influenciar características ecomorfológicas distintas entre as populações. Analisamos a ecomorfologia de Astyanax aff. paranae oriundos de três córregos localizados no município de Apucarana pertencentes a diferentes bacias hidrográficas: córregos Jurema (bacia do rio Pirapó), Biguaçú (bacia do rio Ivaí) e Japira (bacia do rio Tibagi). Para testar as diferenças foram utilizados 15 exemplares de A. aff. paranae de cada população, sendo tomadas 26 medidas morfométricas e calculadas seis áreas, de maneira que foram calculados 22 índices ecomorfológicos. Para evidenciar diferenças ecomorfológicas entre os espécimes foram realizados Análises de Variáveis Canônicas (AVC) e um teste "post hoc" de comparações pareadas de Hotelling. Na análise de comparações pareadas entre as populações de A. aff. paranae nos córregos amostrados, o córrego Japira apresentou diferenças estatísticas significantes em relação ao córrego Biguaçú. As diferenças ecomorfológicas entre as populações do córrego Biguaçu e as dos córregos Jurema e Japira podem estar relacionadas com as características biogeográficas de cada bacia. Além disso, as particularidades de cada ambiente, como as interações bióticas e abióticas provida pela qualidade ambiental nos córregos Jurema e Japira podem ser influências, mesmo que de maneira discreta, frente às peculiaridades ecológicas de cada organismo. Palavras-chave: córregos, rio Ivaí, rio Paranapanema, isolamento geográfico, qualidade ambiental. ABSTRATC: Astyanax paranae Eigenmann, 1914 is a small characid known as lambari-do-rabo-vermelho that occurs in several rivers of Upper Paraná River Basin. Considering that environmental characteristics as resource availability, habitat diversity and many others may select specific attributes enabling morphological differentiation, we tested the hypothesis that different environments may influence distinct ecomorphological characteristics between populations. We analyzed Astyanax aff. paranae belonging to three streams from different basins in the Apucarana city: Jurema (Pirapo river basin), Biguaçu (Ivai river basin) and Japira (Tibagi river basin) streams. To test the ecomorphological difference we used 15 individuals of A. aff paranae of each population, to take 26 morphometric measures and calculate six areas, obtaining 22 ecomorphological rates. We used Canonical Variate Analysis (CVA) and a paired Hotelling's test to evidence ecomorphological differences between the specimens. Japira stream's population of A. aff. paranae presented statistical difference when compared with Biguaçu stream by the analysis of paired comparisons. The ecomorphological diferences be...

Parodontidae is a small group of fish and some species are particularly difficult to identify due to the lack of sufficiently consistent morphological traits. Cytogenetically, the species possess 2n = 54 chromosomes and are either sex-homomorphic or sex-heteromorphic (regarding its chromosomes). We evaluated data on color, tooth morphology, cytogenetics, and mitochondrial markers (COI) in Apareiodon specimens from the Aripuanã River (Amazon basin) and the results were compared to other congeneric taxa. Morphological results show an overlap of body color and tooth morphology to other known Apareiodon . The cytogenetics data showed that the 2n = 54 chromosomes, 50 m/sm + 4 st and, a ZZ/ZW sex chromosome system in Apareiodon sp. are common to other species of the genus. However, the number and chromosomal localization of the 45S ribosomal and p Ph 2004 satellite DNA sites, in addition to W chromosome localization of the p Ph 2004 appear to be exclusive cytogenetic features in Apareiodon sp. Our phylogenetic tree revealed well-supported clades and confirmed, by barcode species delimitation analysis, a new Molecular Operational Taxonomic Unit (MOTU) for Apareiodon sp. (Aripuanã River). As a whole, the above features support the occurrence of a new species of the Apareiodon , thus far unknown for the Parodontidae.

The replacement of tropical forests to production systems is one of the leading causes of riverine ecosystem alterations. However, current assemblages’ composition may also result from the time since these transformations have begun. Therefore, the knowledge of diversified historical scenarios can facilitate the accomplishment of actions that involve the aquatic environments recovery. In this study, an inventory of stream fish was carried out in basins whose deforestation was intensified in the last 20 years, to compose a baseline for ecological and taxonomic studies. The habitat, physical and chemical variables, and the fish assemblages from 60 streams in the northwest region of the state of Mato Grosso, in the Aripuanã and Juruena river basins, were sampled with standardized procedures. For a total of 130 species, a numerical predominance of small-sized Characidae and great rarity were registered, with 50 species represented by less than ten individuals and 19 singletons. Approximately 15% of the sampled taxa were identified only at the generic level, and for several taxa, more detailed taxonomic and molecular studies are required in order to achieve satisfactory identifications. None threatened species were so far reported. On the other hand, two specimens of non-native species were sampled. Although habitat quality is higher in forested streams, no differences in the species richness were registered when compared to the pasture with riparian forest streams or to more deforested streams. However, abundance was greater in these last two streams groups as a result of small-sized characins dominance.

The structure of freshwater assemblages may be driven directly by urbanization or indirectly by a reduction in environmental heterogeneity (EH). Disentangling the effects of urbanization and EH requires uncorrelated proxies of each of these factors. We assessed the effects of the degree of urbanization and EH on the structure of fish assemblages. We sampled fish in 45 streams located in the urban area of Cuiabá. We assessed the effects of urbanization and EH on rarefied fish species richness (Srarefied), the local contribution to beta diversity (LCBD), and composition with linear models and distance-based redundancy analysis. Our indexes of urbanization and EH were not correlated. We found that both Srarefied and the LCBD decreased with an increasing degree of urbanization, but were not associated with EH. We also noted that few native fish species abundances were associated with the EH. Serrapinnus microdon, S. calliurus, Hemigrammus tridens, and Astyanax lacustris were abundant in streams with a lower degree of urbanization. The non-native Poecilia reticulata was more abundant in streams with a higher degree of urbanization. Our results highlight that urbanization leads in negative impacts on fish assemblages, such as decreases in diversity and the dominance of non-native species.

Os Gymnotiformes são conhecidos como peixes elétricos, peixes faca, tuviras ou morenitas, constituindo uma pequena e endêmica porção da ictiofauna Neotropical. Por apresentar uma ampla distribuição geográfica e uma alta riqueza, Gymnotus é o gênero da ordem mais estudado. Uma das espécies que mais se destaca é Gymnotus inaequilabiatus a qual é distribuída nas bacias dos rios Paraná-Paraguai e drenagens costeiras do Uruguai e dos rios do sudeste Brasileiro. Com base em relatos de introdução desta espécie e divergências moleculares em várias bacias hidrográficas, traçou-se a hipótese de que há variação morfológica entre as populações de G. inaequilabiatus oriundas de diferentes bacias. Portanto, objetivou-se analisar morfometricamente as populações de quatro bacias diferentes. Para a avaliação e interpretação dos dados morfométricos foram realizadas análises de componentes principais e análises de variáveis canônicas. As análises não mostraram diferenças significativas entre as populações. Contudo, na análise das variáveis canônicas nota-se uma leve tendência na separação das populações. Os resultados demonstraram que Gymnotus inaequilabiatus não se difere morfologicamente e que não há possibilidade de inferência taxonômica sobre as populações das bacias analisadas, não corroborando com a hipótese inicial. No entanto, os resultados sugerem que G. inaequilabiatus apresenta uma alta capacidade adaptativa, grande capacidade de colonização e resiste a diferentes pressões ambientais. Palavras-chave: alto rio Paraná, morfologia, peixes faca, peixe elétrico, rio Paraguai.