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O advento da agricultura e domesticacao animal influenciou a organizacao social das populacoes humanas tornando-as sedentarias, com elevado crescimento populacional e atualmente concentradas em centros urbanos. O processo de urbanizacao altera paisagens e modifica o uso e ocupacao do solo, dando origem a ambientes urbanos nos quais a acao do homem define a estrutura, o funcionamento e a dinâmica ecossistemica. Apesar da crescente expansao da urbanizacao, nos ainda sambemos muito pouco sobre seus efeitos ecologicos. Neste capitulo exploramos o estado do conhecimento atual acerca dos efeitos da urbanizacao sob os riachos e sua ictiofauna sob a otica da biodiversidade, interacoes ecologicas, adaptacao e conservacao. Tambem discutimos aspectos teoricos, abordagens, metodologias para o estudo dos peixes urbanos. Os topicos apresentados neste capitulo tem o objetivo de introduzir ao leitor os aspectos fundamentais da ecologia de peixes urbanos, bem como apresentar as principais ferramentas de analise, para fomentar o desenvolvimento de estudos futuros.

Estudos sobre producao sao fundamentais para o entendimento de varios aspectos da organizacao e funcionamento dos sistemas aquaticos. O conhecimento sobre esse assunto ainda e muito pouco explorado, especialmente no que se refere aos riachos da regiao Neotropical. Neste estudo, apresentamos os principais marcos teoricos, os diferentes metodos consagrados na literatura, bem como as perspectivas sobre o tema para peixes de riachos neotropicais. Destacamos que todos os metodos disponiveis conduzem a resultados semelhantes e a escolha de um ou outro recai sobre as circunstâncias da pesquisa. Para peixes de riachos tropicais recomendamos o uso do Metodo da Distribuicao de Tamanho. Apresentamos, tambem, um passo-a-passo para o uso do software R (pacote TropFishR) para os calculos de producao. Uma abordagem comparativa e realizada para as taxas de producao conhecidas em regioes de clima tropical, temperado e mediterrâneo, sugerindo-se um padrao inverso entre a diversidade de especies e as taxas de producao desses ambientes. Esperamos, com o presente estudo, estimular pesquisas nessa area do conhecimento, de forma a se incluir informacoes sobre os padroes e processos geradores de producao em riachos neotropicais em um contexto mais amplo da teoria ecologica. FISH PRODUCTION IN STREAMS: REVIEWING PRINCIPLES, METHODS AND PERSPECTIVES: Production studies are fundamental for understanding various aspects of the organization and functioning of aquatic systems. The current state of knowledge on this subject is still little explored, especially regarding streams in the Neotropical region. In this study, we present the main theoretical frameworks, the different methods available in the literature, as well as perspectives on the topic for fish from neotropical streams. We emphasize that all available methods lead to similar results and the choice of one or the other falls on the circumstances of the research. For tropical stream fish we recommend using the Size Distribution Method. We also present a step-by-step guide for using the R software (TropFishR package) for production calculations. A comparative approach is carried out for the known production rates in Tropical, Temperate and Mediterranean regions, suggesting an inverse pattern between the species diversity and the production rates of these environments. We hope, with the present study, to stimulate research in this area of knowledge, to include the patterns and processes that generate production in neotropical streams in a broader context of ecological theory.

The effects of invaders on native species are usually tested using species mean trait values over long time scales. However, considering individual variation over short timescales can help us better understand the interaction between invaders and native species. We compared trophic traits of the non-native guppy (Poecilia reticulata) and the native Brazilian poeciliid Phalloceros harpagos using experiments simulating the early stages of an invasive process. We used short-term mesocosms to simulate an early invasion scenario, where the two species were placed together, and a pre-invasion scenario, where species were kept separated, and analyzed interspecific and intraspecific trophic variability. We also compared the foraging efficiency of species in laboratory experiments. We found no differences on the mean diet of both species between pre and early invasion treatments. At the individual level, in the early invasion scenario, individuals of both species reduced their trophic niche as a probable effect of the presence of the heterospecific. Phalloceros harpagos had higher consumption rates than guppies indicating greater efficiency in feeding on invertebrates. Our results suggest that non-native species were not intrinsically better consumers of high-quality resources. Instead, intraspecific variation might be playing an overlooked role in shaping interactions between species during the early stages of invasion.

Alien species often flourish and become invasive in urban ecosystems. How and why invaders succeed in urban systems is an important, yet poorly understood, question. We investigate whether the success of urban invaders is related to changes in species traits that enhance invasive potential. We also explore whether a trophic mechanism helps explain the success of invaders in urban systems. We use the guppy Poecilia reticulata, a globally distributed alien species that has invaded both urban and non‐urban systems, as our model.We first characterize the effect of urbanization on streams where guppies are present. We measure guppy invasion success using their population density and size‐frequency. Then we assess how traits that are related to the potential of guppies to invade (life history and condition) respond to urbanization. Next, we explore how urbanization affects the availability of food for guppies and their diets. We also test if the presence of other fish species grants biological resistance to invasion by dampening guppy invasive potential.We find that urban streams have high concentrations of ammonium and faecal coliforms, indicating contamination from sewage. On average, guppy populations from urban streams have 26× higher density and larger body sizes than non‐urban populations. Urban guppies are in better condition and have on average five more offspring than non‐urban guppies. Urbanization increases the availability and consumption of highly nutritious food (chironomid larvae) by guppies. We find a positive relationship between the consumption of chironomids and both fecundity and condition. The presence of other fish species in urban streams often has a negative but small effect on guppy traits and density.Our data suggest a relaxation of trade‐offs that shape life‐history traits which is related to increased food resources in urban streams. These indicate that urbanization enhances the invasive potential of guppies through a trophic mechanism that simultaneously increases reproduction and somatic investment. Such mechanism is likely widespread because chironomids are often highly abundant in urban systems. Thus, not only guppies but also other invasive species can take advantage of such a resource to invest in traits that enhance invasion success., This paper looks at how urbanization enhances the success of invaders by changing species traits. The authors find that urbanization provides high food quality and quantity, which allows invasive guppies to increase body size and condition, number of offspring and population density. This suggests that urbanization promotes a highly invasive phenotype.

The current COVID-19 pandemics is a major threat to human populations. The disease has rapidly spread, causing mass hospitalization and the loss of millions of people mainly in urban areas which are hubs for contagion. At the same time, the social distancing practices required for containing the outbreak have caused an eruption of mental illnesses that include symptoms of depression, anxiety and stress. The severity of such mental distress is modulated by the context of media coverage and the information and guidelines from local health authorities. Different urban green infrastructures, such as gardens, parks, and green views can be important for mitigating mental distress during the pandemics. However, it is unclear whether some urban green infrastructures are more efficient than others in reducing mental distress or whether their effectiveness changes with the context. Here we assess the relative importance of different urban green infrastructures on the mental distress of residents of Rio de Janeiro, Brazil. We show that although urban parks and green views are important, home gardens are the most efficient in mitigating mental distress. This is likely related to the practice of self-isolation seen for the residents of Rio de Janeiro. Information on the efficiency of different urban green infrastructures in mitigating mental distress can be important to help guide programs to inform the public about the best practices for maintaining mental health during the current outbreak. This can also help planning cities that are more resilient to future pandemics.

Guppies (Poecilia reticulata) are frequently introduced to both natural and artificial water bodies as a mosquito control. Laboratory studies have demonstrated that guppies can consume large numbers of larval mosquitoes. Our study investigates how intraspecific variability in guppy phenotype affects their importance as a mosquito biocontrol and how habitat conditions (natural ponds vs. water storage containers) may influence insect biomass and guppy feeding. Using a blocked experimental design, we established stream‐side mesocosm ponds with half receiving gravel substrate to simulate pond‐bottom habitat. To provide realistic diet choices and insect abundances, we allowed the mesocosms to colonize naturally with aquatic insect larvae for 1 month before introducing guppies. We tested two distinct guppy phenotypes (from high‐ and low‐predation streams) alongside fish‐free controls. After 1 month, we measured insect biomass in the mesocosms and examined guppy gut contents to document direct predation. While overall insect biomass was not significantly different across the three fish treatments, we observed a significant reduction in mosquito biomass in fish treatments compared to fish‐free controls, as well as intraspecific differences in feeding. Overall insect biomass was significantly higher in mesocosms without gravel, while habitat condition had no effect on mosquito biomass. As guppy phenotype responds to changes in their environments, it is an important consideration for biocontrol policy to anticipate potential ecosystem effects. We close by relating our findings to other studies and by discussing the implications and potential risks of using guppies to control mosquitoes.

Feeding behaviour and diet of Bryconamericus microcephalus differed between canopy conditions. At the open canopy site, a behavioural modification, grazing on algae, was observed. This was also reflected in gut content analysis and suggests behavioural plasticity in response to resource availability.

Deploying mosquito predators such as the guppy ( Poecilia reticulata ) into bodies of water where mosquitoes breed is a common strategy for limiting the spread of disease-carrying mosquitoes. Here, we draw on studies from epidemiology, conservation, ecology and evolution to show that the evidence for the effectiveness of guppies in controlling mosquitoes is weak, that the chances of accidental guppy introduction into local ecosystems are large, and that guppies can easily establish populations and damage these aquatic ecosystems. We highlight several knowledge and implementation gaps, and urge that this approach is either abandoned in favour of more effective strategies or that it is used much more rigorously. Controlling mosquitoes does not need to come at the expense of freshwater biodiversity.

Spatio-temporal changes in the diet, niche breadth and niche overlap of two species of Characidium from three different sites along a Neotropical coastal stream were studied during a dry and rainy season. Seasonal changes were restricted to the occurrence of plant items in the stomach contents. The relative importance of food items in the diet of both species varied across sites, but Diptera, Ephemeroptera, Simuliidae, Trichoptera and Coleoptera larvae were always the main prey items. Contrary to the expected pattern, values of the niche breadth were higher at the site where Characidium species co-existed and niche overlapped at this site indicated 52% (p = 0.52) of feeding overlap.