Nitrogen pollution promotes changes in the niche space of fish communities.

Historically, anthropogenic fixed nitrogen has been purposely increased to benefit food production and global development. One consequence of this increase has been to raise concentrations of nitrogen in aquatic ecosystems. To evaluate whether nitrogen pollution promotes changes in the estimates of niche space of fish communities, we examined 16 sites along a Brazilian river basin highly impacted by anthropogenic activities, especially discharge of domestic and industrial sewage from a region with more than 5 million inhabitants. We analysed the carbon (δ13C) and nitrogen (δ15N) isotope ratios of fish species and both autochthonous (periphyton) and allochthonous (course and fine particulate organic matter) basal food resources. To estimate the magnitude of nitrogen pollution, we measured the nitrate and ammonium concentrations at each site. Sampling was conducted in the dry and wet seasons to evaluate the influence of seasonality. Nitrogen pollution generally increased estimates of niche space, and seasonality influenced only the niche estimates of fish communities from polluted sites. In addition, isotopic analyses of nitrogen polluted sites yielded unrealistic estimates of trophic positioning (detritivores at the top of the food web). We conclude that changes in niche space estimates reflect both alterations in baseline isotopic values and differential trophic behaviour among fishes. Our study suggests that under conditions of high pollution, other factors appear to influence isotopic estimates of niche, such as isotopically distinct sources that have not been sampled, and/or differences in δ15N turnover rates between fish tissue and basal resources, creating isotopic baselines that are challenging to interpret.

Radiotagging a long-distance migratory Characiform fish: reproduction after surgery, tag losses, and effects in weight

Although biotelemetry studies bring useful information, tagging is a highly invasive procedure. For this reason, we assess if intracoelomic tagging alters survivorship, weight gain and/or reproductive capacity of a neotropical migratory fish. In August 2016, 60 fish were equally and randomly distributed among 3 treatments: Control (anesthesia), sham surgery (anesthesia and surgery), and true surgery (anesthesia, surgery and tagging). Surveys for weight and tag expulsion were performed periodically from surgery through spawning (November/2016), with a final survey occurring in May/2017. Mortality was higher in true surgery (25% died) and for males. Twenty percent expelled tags, and initial weight loss followed by gain were verified for all treatments. Females of all treatments spawned, and fecundity and fertility were not different. Then, future studies should consider the losses due to death and tag expulsion when defining the sample number. We also encourage further investigations about differences in mortality between sex and weight variation, as well as any other factor that leads to increase in mortality. This is the first study that investigated tagging effects in reproduction of neotropical fishes, and since the methods and tags used are not species-specific, we infer that similar effects could occur in other species.(AU)

Embora estudos de biotelemetria gerem informações úteis, processos de marcação são invasivos. Por isso, avaliamos se a marcação intracelomática altera sobrevivência, ganho de peso e/ou capacidade reprodutiva de um peixe migrador neotropical. Em agosto de 2016, 60 peixes foram distribuídos igualmente e aleatoriamente entre os tratamentos controle (anestesia), cirurgia-falsa (anestesia e cirurgia) e cirurgia-verdadeira (anestesia, cirurgia e marcação). Vistorias para pesagem e observação de expulsão de marcas foram realizadas periodicamente da cirurgia até a desova (novembro/2016), com uma vistoria final em maio/2017. A mortalidade foi maior nos peixes marcados (25% morreram) e entre machos. Vinte por cento expulsaram as marcas e, para todos os tratamentos, foi observado perda de peso inicial com posterior recuperação. Fêmeas de todos os tratamentos desovaram; fecundidade e fertilidade não foram diferentes. Novos estudos devem considerar as perdas de marcas por mortalidade e rejeição na definição do número amostral. Também recomendamos estudos que investiguem a mortalidade diferencial entre sexos e variação de peso, bem como fatores causadores de mortalidade. Este é o primeiro estudo que investigou efeitos da marcação na reprodução de peixes neotropicais e, uma vez que métodos e marcas utilizadas não são espécie-específicos, inferimos que efeitos similares podem ocorrer em outras espécies.(AU)

Trophic diversity and carbon sources supporting fish communities along a pollution gradient in a tropical river.

Anthropogenic activities can have a great influence on water quality and in the availability of habitat and food resources, which can promote changes in the trophic diversity and carbon sources sustaining aquatic communities. The objective of this study was to evaluate if the trophic diversity and the main carbon sources sustaining fish communities change along a pollution gradient. The study was carried out at eight sites distributed along the Rio das Velhas, a Brazilian river highly impacted by anthropogenic activities, in which the discharge of domestic and industrial sewage from the Metropolitan Region of Belo Horizonte (MRBH) presents a major source of pollution. Using carbon (δ13C) and nitrogen (δ15N) isotope ratios, we identified the major carbon sources/food sources of common fish species and calculated six metrics of trophic diversity. Autochthonous primary producers (algae, periphyton, and macrophytes) were the main carbon sources for all trophic guilds at all sites, but notably, sewage-derived organic matter was an additional significant carbon source to the fish community in the most polluted testing site. Here, the community was composed mainly by detritivorous and omnivorous fishes and exhibited greater ranges of carbon and nitrogen isotopic values, large total areas, high trophic diversity, small trophic redundancy, and less even distribution of trophic niches than the less polluted sites. We conclude that the trophic guilds, trophic diversity metrics, and carbon sources sustaining fish communities in the Rio das Velhas are highly influenced by the presence of pollution. Besides favoring omnivorous and detritivorous fishes, the input of sewage also provided an important food source to sustain the fish community from sites close to the MRBH.

Convergent responses of fish belonging to different feeding guilds to sewage pollution

This study aimed to evaluate if the presence of pollutants promotes changes in feeding habits of fish species from different trophic guilds: the detritivorous species, Hypostomus francisci, and the piscivorous, Hoplias intermedius. Both species were sampled at 12 sites (with different degrees of pollution) in the Rio das Velhas basin, which is heavily polluted by domestic and industrial sewage from the Metropolitan Region of Belo Horizonte (MRBH). Stable isotope analyses of carbon (δ13C) and nitrogen (δ15N) of fish tissue and the main food resources were performed. Fishes from both trophic guilds altered their diets in degraded environments, but the detritivorous species showed greater trophic plasticity. The isotopic niche of both trophic guilds was broadest in unpolluted sites and more δ15N enriched in polluted regions. The detritivorous species presented high niche-breadth in unpolluted sites, probably due to the greater variety of resources consumed. In addition, the δ15N of the detritivorous was more enriched than the piscivorous species in polluted sites. In conclusion, fishes from both trophic guilds presented similar isotopic responses to environmental pollution. However, the detritivorous species was more sensitive to these alterations and therefore, is likely a better indicator of environmental condition than the piscivorous.(AU)

Este estudo teve como objetivo avaliar se a presença de poluentes promove mudanças nos hábitos alimentares de espécies de peixes de diferentes guildas tróficas: a espécie detritívora, Hypostomus francisci, e a piscívora, Hoplias intermedius. Ambas espécies foram amostradas em 12 locais (com diferentes níveis de poluição) na bacia do Rio das Velhas, que é altamente poluída por esgoto doméstico e industrial da Região Metropolitana de Belo Horizonte (RMBH). Foram realizadas análises de isótopos estáveis de carbono (δ13C) e nitrogênio (δ15N) dos tecidos dos peixes e dos principais recursos alimentares. Espécies de ambas guildas tróficas alteraram suas dietas em ambientes degradados, mas a espécie detritívora apresentou maior plasticidade trófica. O nicho isotópico de ambas as espécies foi mais amplo em locais menos perturbados e mais enriquecido em δ15N em regiões poluídas. A espécie detritívora apresentou grande amplitude em seu nicho isotópico em locais menos perturbados, provavelmente devido à maior variedade de recursos consumidos. Além disso, o δ15N da espécie detritívora foi mais enriquecido que a espécie piscívora em locais poluídos. Em conclusão, ambas as espécies apresentaram respostas isotópicas semelhantes à poluição ambiental. No entanto, a espécie detritívora foi mais sensível a essas alterações e, portanto, é provavelmente uma melhor indicadora de condição ambiental do que a espécie piscívora.(AU)

Freshwater fishes of the Bahia State, Northeastern Brazil / Peixes de água doce do Estado da Bahia, Nordeste do Brasil

Abstract: This work was carried out from the assessment of the conservation status of the freshwater ichthyofauna from Bahia State. The inventory data and species distribution were obtained from the specialized scientific literature and representative ichthyological collections. A total of 281 native species was recorded in Bahia State, distributed in the Northeastern Mata Atlantica (NMA) and São Francisco (SFR) freshwater ecoregions. There was a larger number of species in the NMA (187 spp.), composed by several coastal basins, than in the SFR (134 spp.), composed by São Francisco river basin. Among the 30 families recorded, Characidae and Rivulidae were the most representative, with 53 and 48 species, respectively. The conservation status of 214 species was assessed and 33 of them (15%) were included in the IUCN threat categories. Of these, 11 species were classified as vulnerable (VU), 12 as endangered (EN), and 10 as critically endangered (CR). Most threatened species (n = 14) belongs to the family Rivulidae. The larger number of threatened species in the NMA: (n = 23) is mainly related to the high endemism of restricted-range species associated with the human occupation impacts along the coastal regions. In the SFR, most of threatened species are annual killifishes, which are locally disappearing due to increasing degradation of their temporary habitats.

Resumo: Este trabalho foi realizado a partir da avaliação do estado de conservação da ictiofauna de água doce do Estado da Bahia. Os dados de inventário e distribuição das espécies foram obtidos a partir da literatura científica especializada e de coleções ictiológicas representativas. Um total de 281 espécies nativas foi registrado no Estado da Bahia, distribuídas nas ecorregiões de água doce Mata Atlântica Nordeste (NMA) e São Francisco (SFR). A riqueza de espécies foi maior na NMA (187 spp.), composta por diversas bacias costeiras, do que na SFR (134 spp.), composta pela bacia do rio São Francisco. Das 30 famílias registradas, as mais representativas foram Characidae e Rivulidae, com 53 e 48 espécies, respectivamente. O estado de conservação de 214 espécies foi avaliado e 33 (15%) destas foram classificadas em alguma categoria de ameaça da IUCN. Destas, 11 foram classificadas como vulneráveis (VU), 12 em perigo (EN) e 10 criticamente em perigo (CR). A maioria das espécies ameaçadas (n = 14) pertence à família Rivulidae. O elevado número de espécies ameaçadas na NMA: (n = 23) está associado ao alto endemismo das espécies com distribuição restrita e aos impactos da ocupação humana ao longo da região costeira. Na SFR, a maioria das espécies ameaçadas é de peixes anuais, que estão localmente desaparecendo devido à degradação crescente de seus habitats temporários.

Trophic responses to aquatic pollution of native and exotic livebearer fishes.

The objective of this study was to evaluate if aquatic pollution promote diet shifts in two livebearer fishes (Poeciliidae): an exotic species, the guppy (Poecilia reticulata), and a native livebearer (Phalloceros uai). The study was carried out in a Brazilian basin highly impacted by anthropogenic activities, especially discharge of domestic and industrial sewage from a region with more than five million human inhabitants. To evaluate the trophic ecology of both native and exotic species it was analysed carbon (δ13C) and nitrogen (δ15N) stable isotopes of fish tissue, food resources and, sewage. Moreover, stable isotopes analyses were coupled with gut contents of the two species to provide additional information about fish diet. Exotic guppy abundance was high in the most polluted site, where P. reticulata assimilated carbon directly from sewage. The native species was absent in the most polluted site, but presented wider niches than the exotic species in almost all other sites. Gut content analyses indicated high consumption of aquatic insects by both species. However, while the native species consumed a diverse suite of insect taxa, the exotic species consumed mainly Chironomidae larvae. We conclude that aquatic pollution promotes diet shifts in both native and exotic species, with both species changing their trophic niches in a similar way according to the level of degradation of the environment. The ability to directly assimilate sewage, together with its capacity to survive in environments with poor water quality and its reproductive strategy, may favour the establishment of exotic guppies in strongly polluted sites.

Upstream and downstream migration speed of Prochilodus costatus (Characiformes: Prochilodontidae) in upper São Francisco basin, Brazil

Details of migration dynamics of Neotropical fishes are poorly understood. This study aimed to examine upstream (spawning) and downstream (post-spawning) migration speeds, of curimatá-pioa (Prochilodus costatus) in the São Francisco River basin, southeast Brazil. Most upstream movements were recorded in October and November, in two well-defined migration windows, and downstream movements were frequent from December to March. Fish migrated upstream at an average migration speed of 34.4 km day-1 and no significant differences were detected in their speed between sexes and migration window they selected to migrate. No relationship was detected between upstream migration speed and biometric measures of tagged individuals. Upstream migrations speeds were significantly higher for fish that swam longer prior to reach telemetry stations in the same season, indicating that swimming performance may take some time to achieve its peak in upstream migration. Fish migrated downstream at an average migration speed of 97.7 km day-1, what is close to passive swimming in São Francisco River, and no significant differences in speed were detected between sexes or capture sites. The migration speeds measured here are the highest ever recorded for the genus Prochilodus and are among the highest reported for Neotropical migratory fish.(AU)

Detalhes acerca da dinâmica migratória de peixes neotropicais são pouco conhecidos. O objetivo deste estudo foi analisar as velocidades em migração ascendente (reprodutiva) e descendente (pós-reprodutiva) da curimatá-pioa (Prochilodus costatus) no rio São Francisco, Brasil. A migração ascendente concentrou-se nos meses de outubro e novembro, em duas janelas migratórias, e a descendente de dezembro a março. Os peixes alcançaram velocidade migratória média de 34,4 km dia-1 em migração ascendente não sendo observadas diferenças nas velocidades em relação ao sexo e janela migratória em que o peixe migrou. Não foi observada relação entre velocidade migratória e características biométricas dos peixes. Diferenças nas velocidades migratórias ascendentes foram observadas para peixes que nadaram maiores distâncias antes de passar pelas estações de telemetria, indicando que o pico de desempenho natatório é alcançado algum tempo depois de iniciado o movimento ascendente. Em migração descendente a média de velocidade migratória foi de 97,7 km dia-1, próxima à natação passiva, e não foram observadas diferenças entre as velocidades em relação a sexo e ponto de marcação dos peixes. As velocidades migratórias medidas neste estudo são as maiores já registradas para o gênero Prochilodus e estão entre as maiores registradas para peixes migradores neotropicais.(AU)

Complete mitochondrial DNA of Hoplias intermedius (Günther, 1864) (Ostariophysi: Characiformes: Erythrinidae).

Mitochondrial complete genome (mtDNA) of Hoplias intermedius, commonly known as "traírão" is presented. DNA from a muscle tissue sample was sequenced by next-generation sequencing. To corroborate the results, phylogenetic analysis was performed with MEGA6 to compare the complete mitogenome of H. intermedius with genomes of other Characiformes species. The mtDNA molecule was circular and 16,629 bp in length. Gene content included 22 tRNA genes, 2 rRNA genes, 13 protein-coding genes and a D-loop noncoding region. All genes had ATG as the start codon. Six genes carried complete stop codons of AGG (COI), TGA (ND6) and TAA (ND1, ATPase 8, ND4L and ND5), while seven genes had incomplete stop codons. Phylogenetic relationships with other Ostariophysi species placed H. intermedius together with H. malabaricus as a monophyletic group belonging to the order Characiformes.

Complete mitochondrial genome of Salminus brasiliensis (Characiformes, Characidae).

We report the complete mitochondrial genome of the fish Salminus brasiliensis, popularly known as dourado. It is a circular, 17,721 bp long DNA molecule, containing 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and a non-coding Control Region of 2128 bp, a relatively large molecule when compared to other closely related fishes. All protein-coding genes are on the heavy strand, except for Nd6, and all have ATG as the start codon, except for Cox1 gene which has a GTG start codon. Seven protein-coding genes have incomplete stop codons (Nd2, Cox2, Atp6, Nd4, and Cytb have T- -, and Cox3 and Nd3 have TA-). TAG is the stop codon for Nd6 and AGG is the stop codon for Cox1.

Morphological diversity of fish along the rio das Velhas, Minas Gerais, Brazil

The rio das Velhas, located in central Minas Gerais State (Brazil), is a major tributary of the rio São Francisco. Despite several anthropogenic pressures, this basin supports more than 115 fish species. The aim of this study was to compare the morphological space occupied by fish assemblages in four regions (headwaters, upper, middle, and lower course) along the channel of the rio das Velhas. We try to answer the following question: Is there a change in the morphological organization of the fish along the longitudinal gradient of the river? Individuals from 67 species, collected at several sites in the basin from 1999 to 2008, were measured for 11 morphological attributes related to swimming behavior and habitat use. Through the graphs, the first two dimensions of the PCA suggest that the morphological volume occupied by the headwaters region is smaller than the other sections, because of the low richness of the site. However, morphological hypervolumes of the four reaches analyzed by Euclidean distances were not statistically different. The results indicated that only the density of morphological types increases along the rio das Velhas, and there is no difference between the headwaters and upper courses. Therefore, in order to use functional groups related to the morphology of the species as tools to take measures for the conservation and revitalization of the rio das Velhas, it is necessary analyze the density of species within these groups, as well as their composition.

O rio das Velhas, localizado na região central do estado de Minas Gerais (Brasil), é o mais extenso tributário do rio São Francisco. Apesar dos inúmeros impactos antrópicos que sofre, sua bacia abriga uma rica ictiofauna, com mais de 115 espécies conhecidas. O objetivo deste estudo foi comparar o espaço morfológico ocupado pelas assembleias de peixes em quatro regiões (cabeceira, alto curso, médio curso e baixo curso) ao longo da calha do rio das Velhas. Procuramos responder a seguinte pergunta: há uma mudança na organização morfológica da comunidade de peixes ao longo do gradiente longitudinal do rio? Indivíduos de 67 espécies, coletados em diversos trechos da bacia entre 1999 e 2008, foram medidos considerando 11 atributos morfológicos relacionados ao comportamento natatório e uso do habitat. Graficamente, as duas primeiras dimensões da PCA sugerem que o volume morfológico ocupado pela região de cabeceira é menor do que o dos demais trechos, devido à baixa riqueza do local. Entretanto, os hipervolumes morfológicos dos quatro trechos analisados por meio das distancias euclidianas não diferiram estatisticamente. Os resultados indicaram que apenas a densidade de tipos morfológicos aumenta ao longo do rio das Velhas, sendo que não há diferença entre a cabeceira e o alto curso. Portanto, para o uso de grupos funcionais relacionados à morfologia das espécies como ferramentas para tomada de medidas que visem à conservação e revitalização do rio das Velhas, é necessária a abordagem da densidade de espécies dentro destes grupos, assim como sua composição.

Radiotelemetry of a female jaú, Zungaro jahu (Ihering, 1898) (Siluriformes: Pimelodidae), passed upstream of Funil Dam, rio Grande, Brazil

Jaú, Zungaro jahu (Ihering, 1898), a large migratory catfish endemic to the rio da Prata basin, has a fragile conservation status and its ecology is poorly known. We radio-tracked a female jaú with a total length of 1.5 m that was passed upstream of Funil Dam, rio Grande, to describe its migratory movements, habitat use, linear home range, and diel activity. To track the fish, we made five tracking trips in the period from April, 2003 to January, 2004. In addition to the main body of Funil Reservoir, the fish also used a reservoir-river transition zone located in a branch of Funil Reservoir that flooded part of rio das Mortes. Most of the times, we found the fish in the former beds of streams flooded by the reservoir, at depths that ranged from 8-9 m in the reservoir-river transition zone to 18-21 m in Funil Reservoir. Linear home range of the fish was 31.4 km. The onset of activity occurred early in the evening, but we also detected daytime activity. The conclusion from our study was that the passed adult female jaú used reservoir habitats, migrated between the main body and the reservoir-river transition zone, preferred deep habitats, showed a relatively short home range, and had diurnal and nocturnal activities

O jaú, Zungaro jahu (Ihering, 1898), é um bagre migrador de grande porte endêmico da bacia do rio da Prata, possui frágil status de conservação e sua ecologia é pouco conhecida. Nós rastreamos uma fêmea adulta de 1,5 m de comprimento total transposta para montante da barragem de Funil, rio Grande, para descrever movimentos migratórios, uso do hábitat, área de vida e atividade circadiana. Fizemos cinco viagens, de abril de 2003 a janeiro de 2004, para localização do peixe marcado. O indivíduo utilizou a zona de transição reservatório-rio, localizada no braço do reservatório de Funil que alagou parte do rio das Mortes. O peixe também utilizou o corpo principal do reservatório. Nós o encontramos principalmente nos antigos leitos dos rios que foram alagados em profundidades que variaram de 8-9 m, na zona de transição reservatório-rio, a 18-21 m, no corpo principal do reservatório de Funil. A área de vida linear foi de 31,4 km. O período de atividade ocorreu no início da noite mas também encontramos atividade durante o dia. Concluindo, este estudo demonstrou que a fêmea adulta de jaú transposta usou hábitats do reservatório, migrando entre o corpo principal e a zona de transição reservatório-rio, preferiu ambientes profundos, apresentou área de vida pequena, e mostrou atividade diurna e noturna

Evaluation of fish passage through the Igarapé Dam fish ladder (rio Paraopeba, Brazil), using marking and recapture

Rio Paraopeba, a tributary of rio São Francisco, has a six-meter high dam, built in 1978 to divert water to the Igarapé Thermal Power Plant. In 1994, a fish ladder was built at this dam. The results of a marking and recapture program carried out along rio Paraopeba between 1997 and 2001 are described, using information from fish community studies conducted at ten sampling stations between 1994 and 1997. These investigations showed the presence of at least 91 species in the river. During four rainy seasons between 1997 and 2000, fish were caught downstream of the dam, marked with external plastic tags, and immediately released at the same site. The objective was to evaluate fish passage through the ladder, based on recapture information from artisanal and sport fishermen. A total of 3,642 specimens were marked, adding up to a biomass of approximately 1.33 tons. Twenty-six species were used, representing 28.5 percent of the total recorded richness (91 species). Maximum recorded tag retention time was 10 months. Total recapture rate was 4.37 percent in four years, reaching 5.75 percent in the last period (2000-2001). Of all recaptured specimens, 14.0 percent were caught upstream of the dam, evidencing passage through the ladder. The specimens recaptured upstream of the dam belonged to three species: piau-verdadeiro (Leporinus obtusidens), mandi-amarelo (Pimelodus maculatus) and curimatá-pioa (Prochilodus costatus). These species showed linear home ranges of 15.4, 81.5 and 232.0 km, respectively. Most recaptures occurred immediately downstream of the dam, one of the most intensely fished stretches of rio Paraopeba

Desde 1978, o rio Paraopeba, um afluente do rio São Francisco, tem uma barragem de 6 metros de altura para desvio de água para a Usina Térmica de Igarapé. Em 1994, uma escada para peixes foi construída nessa barragem. Os resultados de um programa de marcação e recaptura realizado entre 1997 e 2001 são descritos, utilizando dados prévios de estudos das comunidades de peixes conduzidos em dez estações de amostragem entre 1994 e 1997. Estes estudos demonstraram a presença de pelo menos 91 espécies no rio Paraopeba. Durante quatro estações chuvosas entre 1997 e 2000, peixes foram capturados abaixo da barragem, marcados com marcas externas, e imediatamente soltos no mesmo ponto. O objetivo desse trabalho foi avaliar a passagem pela escada, com base nas recapturas informadas por pescadores artesanais e esportivos. No total foram marcados 3.642 indivíduos, atingindo aproximadamente 1,33 tonelada em biomassa. Vinte e seis espécies foram utilizadas, representando 28.5 por cento da riqueza total registrada (91 espécies). O tempo máximo verificado de retenção da marca foi de 10 meses. A taxa de retorno total foi de 4,37 por cento em quatro anos, atingindo 5,75 por cento no último período (2000-2001). Do total recapturado, 14 por cento ocorreram a montante da escada. As espécies recapturadas a montante foram o piau-verdadeiro (Leporinus obtusidens), mandi-amarelo (Pimelodus maculatus) e curimatá-pioa (Prochilodus costatus). Essas espécies apresentaram área de vida de 15,4, 81,5 e 232,0 km, respectivamente. O maior número de recapturas ocorreu imediatamente a jusante da barragem da UTE Igarapé, um dos locais de pesca mais intensa em todo o rio