Fish and invertebrates are introduced in freshwaters around the world for commercial purposes, despite widely known impacts on food webs and biological invasions. As a proxy for artificial environments, we modeled a typical reservoir in a Brazilian semiarid region using an ecosystem approach. We compared the role of native and nonnative invasive species (NIS) in the food web, between dry and wet periods, and under the influence of an extreme drought period (from 2011 to 2015), simulating the variation in fish biomasses due to decreasing consumption. Key ecosystem groups were fishes (mainly NIS), birds, and insects. Nutrient cycling was dependent on invaders, while the trophic structure was detritus based during the drought. Biomass of detritivores was almost two times higher than herbivores, and native fish species decreased abruptly in response to invaders and volume variation. The dominance of low-trophic levels (TLII) and tilapia-Oreochromis niloticus (Linnaeus, 1758) and other tilapiines-resulted from interactions among invaders, feeding behavior on benthos, and environmental seasonality, tending toward biotic homogenization (''benthification'') at the ecosystem level. An increasing relevance of detritivores with cascading effects in ecosystems subject to drought, multiple

Aim: Disturbances are events that influence the structure of biological assemblages, yet how historical disturbances have affected the functional structure of recent assemblages is still poorly known. We used species functional traits to investigate the effects of historical disturbances, such as past climate change (aridification), on the current structure of stream fish assemblages.Location: Amazon Basin and Brazilian Northeast streams.Methods: We used measures of functional specialization and originality to assess the effects of historical disturbances on the structure of fish assemblages in streams with similar local environmental conditions in each biome (Amazonia and Caatinga).For this, we measured 15 traits related to locomotion, feeding and habitat use for each species sampled. We then compared the functional structure of each assemblage expressed as functional richness (FRic) and evenness (FEve) between biomes.We also used structured and random simulations of species extinctions to identify the influence of the loss of original and specialized species due to historical disturbance. Results:We found high levels of functional specialization in Amazonia (historically more stable) and redundancy in Caatinga (higher frequency of historical disturbances) regional assemblages, regardless of the inter-biome differences in species richness. These results were also detected in local assemblages, suggesting that the effect of historical disturbances influences the structure of fish assemblages, both at small and large spatial scales.Main conclusions: The historical stability in Amazonian fish assemblages may have favoured a higher taxonomic and FRic, as well as greater functional specialization and originality, compared to Caatinga assemblages. Our results reinforce the importance of understanding and evaluating the evolutionary history of ecosystems in order to describe the current functional structure of species assemblages. K E Y W O R D S functional biogeography, functional structure, historical factors, ichthyofauna, Neotropical freshwaters, species loss

A pesca é atividade essencial para as comunidades ribeirinhas da Amazônia, sendo o peixe fonte primordial de proteína animal e importante componente na geração de renda. Devido às variações na abundância e distribuição das espécies de peixe como conseqüência do ciclo hidrológico na região, ocorre sazonalidade na atividade de pesca. Assim, este estudo teve por objetivo identi car quais fatores determinam o tempo de dedicação às pescarias de subsistência ou com ns comerciais, por ribeirinhos de áreas de várzea. Foram entrevistados 244 pescadores de 16 comunidades no Baixo Solimões, quanti cados os volumes capturados de tipos de pescado, por período do ano (seca ou cheia), e identi cados os ambientes de pesca, os aparelhos utilizados e a receita bruta gerada quando da venda do pescado. Os resultados mostraram que há tendência no aumento do número de pescadores comerciais à medida que se aproxima do centro urbano de Manacapuru, sendo dois os fatores determinantes da atividade pesqueira praticada com este m: ambientais, pela disponibilidade e acesso à áreas de pesca, e econômicos, estimulada a venda do peixe pela proximidade de centros de comercialização, o que gera o envolvimento de maior número de agentes na pesca. Os igapós foram importantes para todas as comunidades, sendo os ambientes mais explorados no período de cheia para captura de pescado, fato que ressalta a importância de medidas para sua conservação.

No abstract

Habitat segregation is considered the most prevalent resource-partitioning mechanism for stream fishes and the species morphology can be a strong predictor of their spatial distribution. However, most studies addressing morphology-habitat relationships have defined the space in physiognomically homogeneous units (i.e., mesohabitat), probably not detecting segregation among several closely related species. Here we investigated the ecomorphology and the use of habitat in a fine spatial scale (i.e., microhabitat) by two closely phylogenetically related grazer fishes (the loricariids Parotocinclus maculicauda and Hisonotus notatus), syntopic in an Atlantic Forest stream. We conducted standardized underwater observations in two 50 m long stream sections differing in canopy condition, totaling 273 individual microhabitat records. We clearly detected microhabitat segregation between the species. In both sample sites, H. notatus remained near the stream banks and closer to shelters, while P. maculicauda predominantly occurred in more hydrodynamic microhabitats, facing higher focal current velocities and water turbulence. Differences in focal elevation and water depth (i.e., vertical segregation) were exclusively detected in the deforested site. The spatial segregation was congruent with slight interspecific morphological differences, being in accordance with hypotheses about form-function relationships previously reported for fishes. Given that the diel activity and diet of these grazer species were strongly overlapping, we believe that the observed microhabitat segregation favors resource partitioning between P. maculicauda and H. notatus, facilitating their coexistence in high abundances in the studied system. This study illustrates how the assessment of fine-tuned ecological processes can provide subsidy to management strategies aiming the conservation of tropical stream biodiversity.

Humid highland forest enclaves are remnants of Atlantic Forest found in tablelands within the Caatinga biome (Northeastern Brazil), which emerged during interglacial periods in the Pleistocene. These ecosystems have a highly diverse and endemic fish fauna. Most earlier surveys have focused on the tableland of Borborema (Pernambuco and Paraíba States). In this study we surveyed the fish fauna of the humid forest enclaves in the tablelands of Ibiapaba and Araripe, based on samples collected in the rainy season (March and April) between 2009 and 2014. The 45 sampling points covered rivers, streams and reservoirs in five river basins belonging to three ecoregions. The species were listed according to drainage divide, and endemism was determined for each ecoregion and for the Caatinga. Our area was more species-rich (n=59) than Borborema (n=27). The samples included five introduced species and 29 species endemic to the Caatinga (49.1% of the sampled species). The distribution of Parotocinclus haroldoi was expanded to the Mid-Northeastern Caatinga ecoregion (Timonha river basin, Ceará State). Our study intends to make a significant contribution to current knowledge of the ichthyofauna in humid highland forest enclaves of semiarid Northeastern Brazil, identified as a priority in the conservation of the biodiversity in the Caatinga.

Tidepools are considered ecosystems of high interchangeable fish biota. However, natural and anthropogenic actions that alter negatively marine ecosystems functioning (e.g., algal exploitation) are causing homogenization of fish biodiversity. Here, we describe the functional and taxonomic assembling of fishes in beach rocks of northeastern Brazil. Traits of fish species were retrieved from Fishbase and beta diversity was assessed by the dispersion of abundance, presence-absence and functional diversity in the multivariate space. We explained spatial-temporal variation in: alpha diversity, taxonomic and functional community composition; as well as temporal variation in functional, beta and gamma diversities. We found an annual stability in fish diversity and composition, and that fish biota was assembled mainly per tidepools' depths. Substrate heterogeneity was correlated to depth, highlighting the role of local features as filters to organize the fish fauna vertically in tidepools, especially a cultivation of algae that influences the local assembling. We also highlight the uniqueness status of beach rocks in the Brazilian tropical region.

Several hypotheses are used to explain species richness patterns. Some of them (e.g. species-area, species-energy, environment-energy, water-energy, terrestrial primary productivity, environmental spatial heterogeneity, and climatic heterogeneity) are known to explain species richness patterns of terrestrial organisms, especially when they are combined. For aquatic organisms, however, it is unclear if these hypotheses can be useful to explain for these purposes. Therefore, we used a selection model approach to assess the predictive capacity of such hypotheses, and to determine which of them (combined or not) would be the most appropriate to explain the fish species distribution in small Brazilian streams. We perform the Akaike’s information criteria for models selections and the eigenvector analysis to control the special autocorrelation. The spatial structure was equal to 0.453, Moran’s I, and require 11 spatial filters. All models were significant and had adjustments ranging from 0.370 to 0.416 with strong spatial component (ranging from 0.226 to 0.369) and low adjustments for environmental data (ranging from 0.001 to 0.119) We obtained two groups of hypothesis are able to explain the richness pattern (1) water-energy, temporal productivity-heterogeneity (AIC = 4498.800) and (2) water-energy, temporal productivity-heterogeneity and area (AIC = 4500.400). We conclude that the fish richness patterns in small Brazilian streams are better explained by a combination of Water-Energy + Productivity + Temporal Heterogeneity hypotheses and not by just one.