A new species of Sturisoma Swainson, 1838 (Loricariidae: Loricariinae), from the Madeira River basin, with a discussion of historical biogeography of western Amazonas and Paraguay River basins.

A new loricariin species of Sturisoma is described from the Cautário, Guaporé, Mamoré, Machado and Soteiro rivers, Madeira River basin, in Bolivia and Brazil. The new species is distinguished from its congeners by the presence of a middorsal longitudinal, thin dark brown stripe on the caudal peduncle, extending from two or three plates posterior to the dorsal-fin base, reaching the origin of the caudal fin, or one or two plates anterior to the origin of the caudal fin; small squarish anteriormost abdominal plates; and a middorsal longitudinal dark-brown stripe from first predorsal plate to near the dorsal-fin origin. Furthermore, the new species is diagnosed from congeners by plate morphology, counts on the median series, coalescent plates and ventrolateral thoracic plates, in addition to measurements related to body and head structures. An analysis of genetic distances using cytochrome C oxidase subunit 1 gene marker of the mitochondrial genome between the new species and several congeners is presented, in addition to a likelihood analysis to illustrate the position of the new taxon within Sturisoma. An identification key for species of the genus currently recorded at the upper Amazonas River basin is provided.

Taxonomic and functional turnover of Amazonian stream fish assemblages is determined by deforestation history and environmental variables at multiple scales

High rates of deforestation, either in the past or the present, affect many of the ecological processes in streams. Integrating deforestation history and the current landscape structure enhances the evaluation of ecological effects of land-use change. This is especially true when contemporary landscape conditions are similar but the temporal path to those conditions differs. One approach that has shown promise for evaluating biodiversity responses over time and space is the β-diversity partitioning, which combines taxonomic and functional trait-based approaches. We tested hypotheses related to stream fish assemblages' turnover in watersheds with different environmental conditions and deforestation histories. We sampled fish from 75 watersheds in the Machado River basin, Brazil, and environmental factors were quantified at multiple scales. Taxonomic turnover was higher than expected by chance, whereas functional turnover was lower than expected by the observed taxonomic turnover, indicating that deterministic processes are structuring these assemblages. The turnover, and the environmental factors differed among watersheds with different deforestation histories. Besides being scale-dependent, turnover patterns are also likely dependent on land use dynamics and involve time-lags.(AU)

Altas taxas de desmatamento, seja no passado ou no presente, afetam muitos processos ecológicos em riachos. Integrar o histórico do desmatamento à estrutura atual da paisagem melhora a avaliação dos efeitos ecológicos da mudança do uso do solo. Isto é especialmente verdadeiro quando as condições da paisagem contemporânea são semelhantes, mas seguiram trajetórias distintas. Uma abordagem promissora para avaliar as respostas da biodiversidade ao longo do tempo e espaço é a partição da diversidade-β, que combina abordagens taxonômica e funcional. Testamos hipóteses relacionadas à substituição das assembleias de peixes de riachos em microbacias com diferentes condições ambientais e histórias de desmatamento. Amostramos 75 microbacias na bacia do rio Machado, fatores ambientais foram quantificados em múltiplas escalas. A substituição taxonômica foi maior do que esperada pelo acaso, enquanto a substituição funcional foi menor do que o esperado pela substituição taxonômica, indicando que as assembleias são estruturadas por processos determinísticos. As substituições e fatores ambientais diferiram entre microbacias com históricos de desmatamento distintos. Além de serem escala-dependentes, os padrões de substituição provavelmente são dependentes da dinâmica do uso do solo, envolvendo defasagem temporal.(AU)

Factors determining the structure of fish assemblages in Tarumã River, Jaru Biological Reserve, Machado River drainage, northern Brazil

ABSTRACT Few studies on fish assemblages and relations with environmental factors in aquatic systems in southeastern Amazonia have been carried out when compared to other areas in the Amazon. Therefore, which are the main environmental variables and processes responsible for structuring them remains unknown. We hypothesized that fish assemblages respond the variation in the physical-chemistry variables between seasons of the hydrological cycle in a pristine river in the Amazon. The study was performed on fish assemblages of the Tarumã River, Jaru Biological Reserve, Rondônia. Samplings were carried out in five sites along the river in March and September, 2015, which included fish collection and environmental data measurements. Principal component analysis was performed to ordinate the sites in high water and low water seasons, according to environmental variables. We used a similarity analysis in order to identify the individual contribution of species in hydrological period and a partial redundancy analysis for quantify the relative importance of environmental variables in the species composition. As predicted by our hypothesis, the species composition was influenced by dissolved oxygen and temperature. Myloplus rubripinnis, Serrasalmus compressus, and S. rhombeus were the most abundant during high water, while S. rhombeus, Myloplus lobatus, Prochilodus nigricans, and Hydrolycus armatus were the dominant species during the low water.

RESUMO Poucos estudos sobre assembleias de peixes de sistemas aquáticos do sudeste da Amazônia foram realizados quando comparado a outras áreas na Amazônia. As principais variáveis ambientais e processos responsáveis por sua estruturação permanecem desconhecidas. Nossa hipótese é que as assembleias de peixes respondem as variações das variáveis físico-químicas entre as estações do ciclo hidrológico em um rio preservado na Amazônia. O estudo analisou as assembleias de peixes do rio Tarumã, na Reserva Biológica do Jaru, Rondônia. As amostragens foram realizadas em cinco pontos amostrais ao longo do rio, em março e setembro de 2015, que incluiu coleta de peixes e medições de dados ambientais. A Análise de Componentes Principais ordenou os pontos amostrais nos períodos de cheia e seca, de acordo com as variáveis ambientais. Utilizamos uma análise de similaridade afim de identificar a contribuição individual de cada espécie em cada período hidrológico e uma análise de redundância parcial com o objetivo de quantificar a importância relativa das variáveis ambientais na composição das espécies. Conforme previsto por nossa hipótese, a composição de espécies do rio Tarumã é influenciada pelo oxigênio dissolvido e temperatura. Myloplus rubripinnis, Serrasalmus compressus e S. rhombeus foram mais abundantes durante o período de cheia, enquanto S. rhombeus, Myloplus lobatus, Prochilodus nigricans e Hydrolycus armatus foram as espécies dominantes no período de seca.

Survey of fish species from the Lower Roosevelt River, Southwestern Amazon basin / Levantamento de espécies de peixes do Baixo Rio Roosevelt, Sudoeste da Bacia Amazônica

Abstract: This study presents an inventory of the ichthyofauna of the lower Roosevelt River sub-basin and its associated tributaries. Fish sampling with fishing nets and measurements of environmental parameters of water occurred in November/2012 (rising water), February/2013 (flooding), May/2013 (falling water) and August/2013 (drought). Depth mean was 8.86 m, water transparency was 0.6 m, conductivity was 22.7 µS.cm-1, pH was 6.59, dissolved oxygen was 7.63 mg.l-1 and temperature was 28°C. The total estimated capture area was 68,829.6 m2 during 2,880 hours. The catch per unit Effort (CPUE) was 0.37 individuals m-2.day-1. Species were spatially aggregated in all sampling points and river water levels. A total of 5,183 individuals distributed in 7 orders, 29 families, 104 genders and 188 species were sampled in this survey. The diversity index was 4.121 and equitability index was 0.789. The Characiforms order was the most abundant with 106 species, followed by Siluriforms with 63 species and Cichliforms with 23 species. The most abundant species was Serrasalmus rhombeus (Linnaeus, 1766) with 327 individuals (5.9%), followed by Chalceus epakros (Cope, 1870) with 309 individuals (5.6%) and Acestrorhynchus microlepis (Schomburgk, 1841) with 250 individuals (4.5%). Trophicity was characterized by omnivorous (28.6%), piscivorous (14.3%), carnivorous (13.8%) and detritivorous (12.8%). According to IBAMA's regulation, 29.25% of captured species presents ornamental potential.

Resumo: Este estudo apresenta um inventário da ictiofauna da sub-bacia do baixo Rio Roosevelt e seus tributários associados. As coletas de peixes com malhadeiras e as medições de parâmetros ambientais da água ocorreram em Novembro/2012 (enchente), Fevereiro/2013 (cheia), Maio/2013 (vazante) e Agosto/2013 (seca). A média da profundidade foi 8,86 m, da transparência da água foi 0,6 m, da condutividade foi 22,7 µS.cm-1, do pH foi 6,59, do oxigênio dissolvido foi 7,63 mg.l-1 e da temperatura da água foi 28°C. A área total de captura estimada foi 68.829,6 m2 durante 2880 horas. A captura por unidade de esforço (CPUE) foi 0,37 indivíduos m-2.dia-1. As espécies foram espacialmente agregadas em todos os pontos de coleta e períodos de coleta. Um total de 5183 peixes em 7 ordens, 29 famílias, 104 gêneros e 188 espécies foram coletados. O índice de diversidade foi 4,121 e o índice de equidade foi 0,789. As ordens Characiforme, Siluriforme e Cichliforme foram as mais abundantes. As espécies Serrasalmus rhombeus Linnaeus 1766 com 327 indivíduos (5,9%), Chalceus epakros (Cope 1870) com 309 indivíduos (5,6%) e Acestrorhynchus microlepis Schomburgk 1841 com 250 indivíduos (4,5%) foram as mais abundantes. Os onívoros (28,6%), piscívoros (14,3%), carnívoros (13,8%) e detritívoros (12,8%) foram os indivíduos mais abundantes. De acordo com o IBAMA, 29,25% das espécies capturadas tem potencial ornamental.

Fish collection of the Universidade Federal de Rondônia: its importance to the knowledge of Amazonian fish diversity / A coleção ictiológica da Universidade Federal de Rondônia: sua importância para o conhecimento da diversidade de peixes da Amazônia

Biological collections preserve the biodiversity of a nation. The fish collection of the Universidade Federal de Rondônia, recently established, contains about 41% of freshwater fish species known to occur in Brazil, and 24% of South America. The biological material is distributed into 1,067 species, 21,963 lots and 149,192 specimens, gathered during five years of work. From this collection, 99% of the lots have georeferenced location, and 94% of the species were sampled in the Madeira River basin, the largest tributary in flow, drainage area and sediment discharge of the Amazonas River basin. Among the 1,008 species collected in the Madeira River basin, 80% were reviewed by Brazilian, North American and French experts, and represents the highest richness among tributaries of the Amazonas River and other rivers worldwide. Fish collection from the Madeira River basin deposited in the ichthyological collection of the Universidade Federal de Rondônia accounts for about 75% of the lots and specimens of fish from that basin available for study in collections worldwide.

Coleções biológicas preservam a biodiversidade de uma nação. A coleção ictiológica da Universidade Federal de Rondônia, recentemente estabelecida, contém cerca de 41% das espécies de peixes de água doce conhecidas para o Brasil e 24% da América do Sul. O material biológico encontra-se distribuído em 1.067 espécies, 21.963 lotes e 149.192 exemplares, organizados durante 5 anos de trabalho. Desse acervo, 99% dos lotes possuem localidade georreferenciada e 94% das espécies foram coletadas na bacia do rio Madeira, o maior afluente em vazão, área de drenagem e descarga de sedimentos da bacia Amazônica. Do total de 1.008 espécies coletadas na bacia do rio Madeira, 80% foram revisadas por especialistas brasileiros, norte-americanos e franceses, e constitui a maior riqueza de espécies conhecida para um afluente do rio Amazonas e entre outros rios do mundo. O acervo de peixes da bacia do rio Madeira depositado na Coleção de peixes da Universidade Federal de Rondônia representa cerca de 75% dos lotes e de exemplares de peixes dessa bacia disponíveis para estudos em coleções ictiológicas do mundo.

(210)Pb and compositional data of sediments from Rondonian lakes, Madeira River basin, Brazil.

Gold exploration has been intensive in Brazilian Amazon over the last 40 years, where the use of mercury as an amalgam has caused abnormal Hg concentrations in water bodies. Special attention has been directed to Madeira River due to fact it is a major tributary of Amazon River and that since 1986, gold exploration has been officially permitted along a 350km sector of the river. The (21)(0)Pb method has been used to date sediments taken from nine lakes situated in Madeira River basin, Rondônia State, and to verify where anthropogenic Hg might exist due to gold exploitation in Madeira River. Activity profiles of excess (21)(0)Pb determined in the sediment cores provided a means to evaluate the sedimentation rates using a Constant Flux: Constant Sedimentation (CF:CS) and Constant Rate of Supply (CRS) of unsupported/excess (21)(0)Pb models. A significant relationship was found between the CF:CS sedimentation rates and the mean values of the CRS sedimentation rates (Pearson correlation coefficient r=0.59). Chemical data were also determined in the sediments for identifying possible relationships with Hg occurring in the area. Significant values were found in statistical correlation tests realized among the Hg, major oxides and Total Organic Carbon (TOC) content in the sediments. The TOC increased in the sediment cores accompanied by a loss on ignition (LOI) increment, whereas silica decreased following a specific surface area raising associated to the TOC increase. The CRS model always provided ages within the permitted range of the (21)(0)Pb-method in the studied lakes, whereas the CF:CS model predicted two values above 140 years.