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

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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.

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.