Solimoes River Research Articles

RELAÇÃO PESO-COMPRIMENTO DAS ESPÉCIES DE PEIXES QUE OCORREM AO LONGO DO AUATI-PARANÁ NO MÉDIO SOLIMÕES, AMAZONAS, BRASIL

Length‐weight relationships were estimated for 47 fish species for Auati-Parana channel in Central Brazilian Amazonia. Sampling was carried quarterly during 2013 year, using seine net (3 mm stretch mesh size) for the collections in floating vegetation and hand nets in litter of the littoral zone. This study provides new information on the length–weight relationships for 31 species, in addition, provides the new maximum standard lengths for six species Keywords: Ichthyofauna; Neotropical fishes; Solimoes River Basin.

PRIMER REGISTRO DE SPINITECTUS RODOLPHIHERINGI VAZ & PEREIRA, 1934 (SPIRURIDA: CYSTIDICOLIDAE) EN AUCHENIPTERUS NUCHALIS (SPIX & AGASSIZ, 1829) (SILURIFORMES: AUCHENIPTERIDAE) DE LOS LAGOS DE LA LLANURA ALUVIAL DEL AMAZONAS

Fish are the vertebrates that have the greatest number and diversity of parasitic species. Auchenipterus nuchalis (Spix & Agassiz, 1829) is a small fish that occurs in South America, popularly known as “Peruvian mandi”. It has twilight habits and its diet is basically composed of aquatic insects and microcrustaceans, which are intermediate hosts of several parasitic species. Although fish are the vertebrate group with the highest number of parasitic species, most of these species are still unknown, therefore, the main objective of this study was to know and identify the Nematoda species that parasitize A. nuchalis and calculate the parasitological indices of each species. 38 A. nuchalis were captured in four expeditions in September, October, November and December 2016, in the Catalao lake complex in the municipality of Iranduba, Amazonas, on the left bank of the Solimoes river and on the right bank of the Negro river, Brazil. The fish measured, on average, 11.8 - 18 (15.1 ± 1.35) cm in standard length and weighed 30.1 – 71.0 (47 ± 10.66) g. The individuals' digestive tract was preserved in 70% ethanol and transported to the laboratory for analysis. Of the total fish collected and examined, 31 were parasitized. Temporary and permanent slides were mounted to identify the parasitic specimens. The measurements of the individuals were made with the aid of a micrometric eyepiece, coupled to an optical microscope. Eighteen individuals of Spinitectus rodolphiheringi Vaz & Pereira, 1934 parasitizing the intestine and stomach of the hosts were collected. Presenting an infection prevalence rate of 26.3%, which characterizes it as a satellite species. Furthermore, this is an unpublished record of this parasite for A. nuchalis and for the Amazon region.

A Dinâmica das Formas Espaciais Flutuantes nos Lagos Urbanos do Solimões no Amazonas

Nas águas próximas às principais cidades da região do Médio Solimões no Amazonas, Tefé e Coari, centenas de flutuantes exercem funções domiciliares, comerciais, institucionais e de serviços. Compreender o papel dos flutuantes dos lagos urbanos de Tefé e Coari para o desenvolvimento regional e para a integração territorial é o objetivo deste artigo. Primordialmente, realiza-se a identificação das funções e estruturas dos flutuantes nos lagos urbanos destas cidades. Posteriormente, elabora-se a identificação e classificação das formas espaciais flutuantes. Esta análise providencia subsídios para a compreensão das relações sociais e econômicas úteis ou não ao desenvolvimento e à integração territorial nesta fração da formação socioespacial brasileira.

Predicting Channel Conveyance and Characterizing Planform Using River Bathymetry via Satellite Image Compilation (RiBaSIC) Algorithm for DEM-Based Hydrodynamic Modeling

Digital Elevation Models (DEMs) are widely used as a proxy for bathymetric data and several studies have attempted to improve DEM accuracy for hydrodynamic (HD) modeling. Most of these studies attempted to quantitatively improve estimates of channel conveyance (assuming a non-braided morphology) rather than accounting for the actual channel planform. Accurate representation of river conveyance and planform in a DEM is critical to HD modeling and can be achieved with a combination of remote sensing (e.g., satellite image) and field data, such as water surface elevation (WSE). Therefore, the objectives of this study are (i) to develop an algorithm for predicting channel conveyance and characterizing planform via satellite images and in situ WSE and (ii) to estimate discharge using the predicted conveyance via an HD model. The algorithm is named River Bathymetry via Satellite Image Compilation (RiBaSIC) and uses Landsat satellite imagery, Shuttle Radar Topography Mission (SRTM) DEM, Multi-Error-Removed Improved-Terrain (MERIT) DEM, and observed WSE. The algorithm is tested on four study areas along the Willamette River, Kushiyara River, Jamuna River, and Solimoes River. Channel slope and predicted hydraulic radius are subsequently estimated for approximating Manning’s roughness factor. Two-dimensional HD models using DEMs modified by the RiBaSIC algorithm and corresponding Manning’s roughness factors are employed for discharge estimation. The proposed algorithm can represent river planform and conveyance in single-channeled, meandering, wandering, and braided river reaches. Additionally, the HD models estimated discharge within 14–19% relative root mean squared error (RRMSE) in simulation of five years period.

The influence of seasonal river flooding in food consumption of riverine dwellers in the central Amazon region: an isotopic approach

In recent decades, the nutritional transition has been encroaching on remote rural areas of developing countries where feeding patterns are shifting from unprocessed foods to industrialized processed goods. Such changes in the Amazon region have been detected, for instance, by comparing the natural carbon (13C:12C) and nitrogen (15N:14N) isotopic ratios of people living in riverine communities with urban dwellers their putative diet. In this study, we considered how landscape variables impacted food consumption by comparing fingernail isotopic ratios of individuals in the rural settlement of Costa do Caldeirao located in the floodplain (varzea) of the Solimoes River, and in the rural settlement of Paquequer located in a non-flooded area (terra-firme) near the Madeira River banks. A total of 70 fingernails were sampled for carbon and nitrogen isotopic analysis during the low water period and again during the high water period from the same residents of the varzea and terra-firme. The consumption of C4-like resources (e.g., frozen chicken and canned meat) increased in both rural settlements during the high water period when C3-like resources (fish, cassava, rice, beans) are less available due to the flooding of lowland areas, but this difference was more pronounced in the terra-firme. The higher consumption of C4-like resources in the varzea compared to the terra-firme shows how seasonal flooding is a key factor influencing food security and health, due to stark variations in river water levels. While fish and farinha are still important staple foods, differences within rural settlements suggest that, besides seasonal variation and changes in water levels, other factors such as age, origin, and income may be crucial to understanding individual dietary behavior change in line with the nutritional transition model.

Climate and hydrologic controls on late Holocene sediment supply to an Amazon floodplain lake

Organic and inorganic geochemical analyses on sediments from Preto Lake, a central Amazon basin floodplain water body, were used to document hydrological changes of the Solimoes River during the late Holocene. Between 3600 and 400 cal yr BP, Preto Lake received smectite-rich sediment from the Solimoes River, with high concentrations of Al (~ 53 × 103 ppm) and Si (~ 210 × 103 ppm). The high detrital input suggests there was a direct connection between Preto Lake and the main river channel. High river inflow maintained lake stage and was responsible for the contribution to sediments of phytoplankton-derived organic matter. Low sediment organic carbon concentrations characterized this period (mean ~ 3.8 wt%), probably because of dilution by river-borne lithogenic matter. Although the river inputs remained high, abrupt increases in TOC content around 1800 and 1200 cal yr BP suggest brief increases in fluvial nutrient supply to Preto Lake. During the last 400 cal yr, substantial declines in smectite (mean 40%), Al (~ 29 × 103 ppm) and Si (138 × 103 ppm) suggest the establishment of a semi-isolated lake, with reduced river inflow. A large proportion of C3-plant-derived organic matter, supplied by runoff from the kaolinite-rich watershed, was observed during this period, and was accompanied by high autochthonous primary production, driven by development of an aquatic macrophyte community. This change in sediment organic matter source accounted for the greater TOC content (~ 20%) of sediments deposited during this period. Although Holocene climate change was an important control on fluvial sediment supply to upper and lower Amazon Basin floodplain lakes, sedimentation processes in Preto Lake can also be linked to changes in the river’s course. The transition to a semi-isolated lake could have been a consequence of lateral and vertical sediment accretion, which formed a natural levee that blocked fluvial input to Preto Lake.

CARACTERIZAÇÃO HIDROLÓGICA DOS SISTEMAS LACUSTRES DO ARQUIPÉLAGO DE ANAVILHANAS COM BASE EM SENSORIAMENTO REMOTO

Este estudo caracterizou os sistemas lacustres do Arquipélago de Anavilhanas e avaliou a variação espacial da superfície de água em condições próximas as médias fluviométricas interanuais para cada período, utilizando imagens do Landsat 08 e dados fluviométricos do Rio Negro. A variação sazonal observada para todo o arquipélago foi na ordem de 10%. Para os sistemas lacustres e áreas de “águas mortas” foi de 17%. Para 447 lagos identificados, 46% possuem conexão com os canais do arquipélago durante o período de águas baixas e 54% ficam isolados neste período. Foram apontados três domínios para o Arquipélago. No domínio A (montante) o rio é relativamente estreito e as ilhas e lagos são menores. No domínio B (centro) o rio é relativamente mais largo e as ilhas e lagos são de grandes extensões. No domínio C (jusante) o rio apresenta largura semelhante ao domínio A e as ilhas estreitas, alongadas e sinuosas com lagos alongados e abertos. O domínio C apresentou menor variação sazonal e um maior número de lagos conectados, o que pode estar associado às características geomorfológicas e as condições hidráulicas dadas pela influência do barramento hidráulico do Rio Solimões.

River Discharge Estimation based on Satellite Water Extent and Topography: An Application over the Amazon

Abstract River discharge (RD) estimates are necessary for many applications, including water management, flood risk, and water cycle studies. Satellite-derived long-term GIEMS-D3 surface water extent (SWE) maps and HydroSHEDS data, at 90-m resolution, are here used to estimate several hydrological quantities at a monthly time scale over a few selected locations within the Amazon basin. Two methods are first presented to derive the water level (WL): the “hypsometric curve” and the “histogram cutoff” approaches at an 18 km × 18 km resolution. The obtained WL values are interpolated over the whole water mask using a bilinear interpolation. The two methods give similar results and validation with altimetry is satisfactory, with a correlation ranging from 0.72 to 0.89 in the seven considered stations over three rivers (i.e., Wingu, Negro, and Solimoes Rivers). River width (RW) and water volume change (WVC) are also estimated. WVC is evaluated with GRACE total water storage change, and correlations range from 0.77 to 0.88. A neural network (NN) statistical model is then used to estimate the RD based on four predictors (SWE, WL, WVC, and RW) and on in situ RD measurements. Results compare well to in situ measurements with a correlation of about 0.97 for the raw data (and 0.84 for the anomalies). The presented methodologies show the potential of historical satellite data (the combination of SWE with topography) to help estimate RD. Our study focuses here on a large river in the Amazon basin at a monthly scale; additional analyses would be required for other rivers, including smaller ones, in different environments, and at higher temporal scale.

Length‐weight relationships of five fish species from lakes of the Central Amazonian floodplains

Parameters of the length‐weight relationship (LWR) were calculated for five fish species from Amazon Basin. Samplings were carried out in ten lakes of the Solimoes River floodplains during the four seasons of the hydrological cycle: rising water, high water, receding water, and low water, during two periods. The first period of eight years included samplings performed from 2001 to 2008 and the second sampling period of two years was from 2012 to 2013. Specimens were captured using gillnets (mesh sizes ranging from 30 to 120 mm between opposite knots) and standardized dimension of 20 m in length × 2 m in height. This study provides the LWR parameters for Acarichthys heckelii, Leporinus trifasciatus, Brycon amazonicus, Curimatella meyeri and Osteoglossum bicirrhosum.

Distribuição de larvas de Brycon amazonicus (PISCES: BRYCONIDAE) no entorno da Reserva de Desenvolvimento Sustentável Mamirauá: base ecológica para manejo

A conservação dos recursos pesqueiros no médio Amazonas está relacionada ao conhecimento acerca dos seus estoques pesqueiros mais importantes, incluindo também o conhecimento sobre os padrões de recrutamento e desenvolvimento dos primeiros estágios de vida das espécies de maior importância econômica para a região. O presente trabalho amplia o conhecimento ecológico sobre a distribuição das larvas de Brycon amazonicus (matrinxã) a fim de verificar a importância dos ambientes fluviais para o recrutamento biológico dessa espécie, auxiliando no manejo sustentável e na conservação desse recurso pesqueiro da Amazônia Central. Este trabalho foi realizado no entorno da Reserva de Desenvolvimento Sustentável do Mamirauá (RDSM), e os dados obtidos foram provenientes de coletas diurnas e noturnas realizadas durante o período de enchente de 2011, no trecho médio do Rio Solimões e Baixo Rio Japurá, por meio de arrastos horizontais na superfície e em profundidade (8m), utilizando rede de plâncton 300µm em 16 estações de amostragem. Foram capturadas 310 larvas de matrinxã, sendo 148 indivíduos coletados no Rio Solimões e 162 no Rio Japurá. Observou-se que não houve um padrão claro de distribuição entre os habitats amostrados; entretanto, foi constatado variação da abundância larval indicando distribuição espacial (estratos da coluna d’água) e temporal (ciclo diário), com as maiores abundâncias registradas na subsuperfície da água durante o período noturno. Larvas registradas em estágios mais avançados de desenvolvimento refletem a importância da área de estudo para o recrutamento biológico, servindo como área de criação e alimentação para as larvas de matrinxã, sendo consideradas Habitats Essenciais para Peixes (EFHs) fundamentais para o manejo sustentável e conservação desse recurso pesqueiro da Amazônia Central.

POVOS TICUNA NA TRÍPLICE FRONTEIRA: DESAFIOS PARA O ESTADO E PARA O DIREITO

O trabalho em questão deu-se pela importância do tema para as discussões no Direito brasileiro. Tratar de indígenas entre fronteiras é sempre um problema quando se faz a leitura de um Estado, baseado nos ideais de modernidade, nos quais não se consegue incluir as diferenças e especificidades territoriais, culturais e sociais indígenas. Desta forma, através de pesquisa bibliográfica e documental, pretende-se abordar a questão indígena na tríplice fronteira Brasil (Tabatinga), Peru (Santa Rosa) e Colômbia (Letícia), na região do Alto Rio Solimões para demonstrar a mobilidade dos Ticuna entre fronteiras. Outra abordagem dada é a necessidade da mudança estrutural do Estado e seus direitos para efetivação de direitos socioambientais, dentro dele, os direitos indígenas que são incompatíveis com a racionalidade individualista e universalista do Estado eurocêntrico. O objetivo do trabalho é demonstrar que o Estado e seu direito são insuficientes para lidar com a mobilidade Ticuna na região da tríplice fronteira, demonstrando que este fato ocorre independente das delimitações territoriais estabelecidas pelo Estado, e também, investigar como os três países têm lidado com a questão Ticuna em seus territórios.

A diní­¢mica sazonal das pescarias de pequena escala na Amazônia é definida pelo pulso hidrológico

O presente estudo analisou a diní­¢mica de uma pescaria de pequena escala na Amazônia em associação com o ciclo hidrológico. Dados de desembarque pesqueiro foram coletados diariamente no perí­­odo de fevereiro/2007 a janeiro/2008 no Porto Panairzinha em Manacapuru, Amazonas í Brasil (3°18’33”S e 60°33’21”W). Os resultados mostraram que a frota atuante no Lago Grande é composta por canoas motorizadas e barcos de pesca, sendo o número de canoas superior ao de barcos. A média do pescado desembarcado foi de 274,15 ton.ano-1, ocorrendo menor produção nos perí­­odos de enchente/cheia e maior na vazante/seca. As principais espécies desembarcadas foram: Colossoma macropomum (tambaqui = 17,8%), Cichla monoculus (tucunaré = 15,5%), Prochilodus nigricans (curimatã = 12,2%), Astronotus ocellatus (acará-açu = 8,7%) e Osteoglossum bicirrhosum (aruanã = 8,4%), predominando a malhadeira (97%) nessas capturas. Foi observado que a sazonalidade do Rio Solimões influi diretamente nas pescarias e na disponibilidade do pescado. Nesse sentido, decisões envolvendo o manejo pesqueiro nessa região devem estabelecer medidas que assegurem a sustentabilidade da pesca local, considerando como essencial a relação entre o peixe, o ambiente e os aspectos socioeconômicos das pescarias de pequena escala.

The influence of inundation and lake morphometry on the dynamics of mercury in the water and plankton in an Amazon floodplain lake

Seasonal flooding changes chemical and morphometric characteristics of the tropical floodplain lakes, affecting stratification which can influence mercury dynamics. We investigate the influence of flooding on the mercury dynamics in an Amazon floodplain lake. Three points on the lake, the Solimoes River, and the connecting channel to the river were sampled along the annual flood pulse. During high-water, the lake was deep (12.7 m, on average) and the area farthest from the river was stratified with low oxygen and high methylmercury concentrations ([MeHg]) at depths below 7 m (0.37 ng l−1, on average). The two sites closest to the river were destratified and the [MeHg] was lower (0.077 ng l−1, on average along all depths). At low-water, the lake was shallower (3 m, on average) and destratified, with higher oxygen concentrations, and no difference in [MeHg] along the water column at all lake sites. Independent of season, the [MeHg] in the connecting channel was higher than those in the river. The [MeHg] in phytoplankton varied in response to changes in biomass, showing a biodilution effect. Variations in lake morphometry controlled the stratification and [MeHg] in the lake during the high-water. Floodplain lakes export hypolimnetic MeHg to their associated rivers during high-water.

Late Holocene paleoenvironments of the floodplain of the Solimões River, Central Amazonia, based on the palynological record of Lake Cabaliana

The core PD-67 of 160 cm depth was collected from the delta of Lake Cabaliana situated on the Solimoes River. Seventeen samples were removed for palynological and sedimentological analysis and three for radiocarbon analysis. Two dry periods, both in the Late Holocene, were observed (2800-2550 cal yr BP, 1450-550 cal yr BP) separated by a wetter phase (2550-1450 cal yr BP). In 2800-2550 cal yr BP, varzea forests of Alchornea, Symmeria, Cecropia, Alternanthera and Asteraceae were predominant. Beginning in 2,550-1450 cal yr BP, the varzea was characterized by pioneer elements, such as Cassia, Laetia, Mabea, Symmeria and Cecropia, and by the expansion of Poaceae, Cyperaceae, Sagittaria, Montrichardia and Asteraceae. In 1450-550 cal yr BP the succession of varzea continued with Pseudobombax, Laetia, Luehea/Lueheopsis and Ryanaea increasing simultaneously with the terra firme vegetation of Rutaceae, Sapotaceae, Styrax, Scleronema, Anthurium, Araceae, pteridophytes and Pariana. The successional dynamics at Lake Cabaliana indicated that the local varzea had become established recently, and is composed of a mosaic of different successional stages of vegetation influenced mainly by flood pulse and variation in rainfall. It is therefore possible to propose that the recent climate history of Central Amazonia reflects changes in rainfall patterns in the basin.

Evaluation of the organic matter sources and δ13C composition of individual alkanes for the baseline assessment of hydrocarbons in a pristine area from Amazon region, Brazil

This study focuses on the surroundings of the Urucu oil and gas province and the adjoining Solimoes terminal in the Amazon region of Brazil, which is of great global importance due to its biodiversity richness and freshwater resources. There are few results related to aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), and there are no results for individual stable isotopic compositions (δ13C) in the studied region. Results showed a distribution of n-alkanes that is characteristic of a major input from higher plants. Furthermore, δ13C values of individual n-alkanes varied between −35.0 and −23.1 ‰, suggesting a dominance of 12C-enriched n-alkanes indicative of an origin from lacustrine algae. The levels of some PAHs (4.64–31.70 ng g−1) which are classified as priority pollutants by the United States Environmental Protection Agency (US-EPA) and perylene (biogenic PAH) were measured in surface sediments to identify pollution sources and determine baseline data looking for future management strategies. The majority of the compounds present in the samples from Coari Lake and the Solimoes River are of biogenic origin. However, a minor anthropogenic contribution of aromatic hydrocarbons derived from biomass burning (anthracene, phenanthrene, fluoranthene, pyrene, chrysene, benzo[b]fluoranthene and benzo[k]fluoranthene) was detected. No petrogenic contribution was found in the samples.

Amazon floodplain fish diversity at different scales: do time and place really matter?

Amazonian floodplain lakes, which are of different types based on their proximity to the main river channels, are subjected to a strong seasonal hydrologic cycle and have different habitat types within them. We hypothesized that these two spatial scales (lake type, and habitat type within lakes), and the temporal scale associated with hydrological seasons help explain the high fish diversity of the Amazon basin. We sampled three lake types categorized by proximity and connectivity with the Solimoes River (island, coastal, and mainland) in 2011 during both high and low water seasons. Within these lakes, we sampled three habitat types (open water, flooded forest, and macrophyte banks). Although comparisons of diversity indices revealed few differences with respect to overall species numbers, actual species composition, which is not included in calculation of diversity indices, differed markedly at all three scales. Although many species (86) were common to all three types of lakes, each type also had many unique species (11–20), as did within-lake habitat type (10–15) and hydrologic season (26 each). Thus, these temporal and spatial scales are important to the detection and understanding of fish species diversity in this region, and will be important to keep in mind when designing preserves.

Variação espacial de cátions, ânions e variáveis físico-químicas no rio Solimões-Amazonas entre Manaus e Jutaí, bacia amazônica

Cátions e ânions majoritários são espécies químicas de grande importância nos diversos compartimentos aquáticos, porém, pouco abordados de forma exclusiva na bacia amazônica. Neste sentido, o objetivo deste estudo foi avaliar a dinâmica espacial de Na+, Ca2+, K+, Mg2+, Cl- e SO4 2- em um trecho do rio Solimões-Amazonas, levando-se em consideração a alcalinidade, potencial hidrogeniônico (pH), condutividade elétrica (CE), sólidos totais em suspensão (STS) e carbono orgânico total (COT). As coletas foram realizadas em maio, julho e setembro de 2012 em sete pontos na calha principal do rio Solimões-Amazonas e na foz de alguns dos principais tributários: rios Jutaí, Juruá, Japurá e Purus. Os cátions e ânions foram analisados por cromatografia de íons, STS por gravimetria, pH por potenciometria, alcalinidade por titulação potenciométrica, CE por condutimetria e o COT por oxidação catalítica por combustão. As concentrações médias dos cátions seguiram esta ordem Ca2+>Na+>Mg2+>K+ e dos ânions SO4 2->Cl-. De montante à jusante a tendência foi diminuição nas concentrações de cátions e ânions, das variáveis pH, CE, STS e alcalinidade, além do aumento das concentrações de COT. O presente estudo evidenciou mudanças nas características químicas sofridas pelo rio Solimões em seu curso. O aporte dos tributários pode ser apontado como um dos fatores responsáveis por essas modificações.

Population dynamics and stock assessment of Colossoma macropomum caught in the Manacapuru Lake system (Amazon Basin, Brazil)

AbstractColossoma macropomum is the second largest scaled fish in the Amazon basin. Reduced harvests in recent decades suggest that populations of this species are already overexploited in some areas. In this study, the population dynamics of C. macropomum was investigated using length and weight data for fish caught in the Manacapuru Lake system, a large ria lake located along the lower reach of the Solimões River. A total of 1270 individuals of C. macropomum with standard lengths varying from 17 to 62 cm and mean length of 31.0 ± 6.7 cm were sampled. Weights varied from 165 to 8195 g, and mean weight was 1148.3 ± 883.8 g. Maximum sustainable yield was estimated at 285.8 g recruit−1, corresponding to a fishing mortality of 0.51 year−1. A scenario analysis based on changes in fishing mortality and age at first capture, two parameters potentially addressed by fishing management strategies, suggested that any improvement in fishing yield depends on increases in age at first capture.

Provenance studies in Amazon basin by means of chemical composition obtained by INAA

This study determines the provenance of the 106 sediments samples deposited by the Solimoes and Negro rivers in the tectonic depressions in Manaus, Amazon state, Brazil. Twenty-four chemical elements in the sediment samples collected before the confluence of Negro and Solimoes rivers have been determined using instrumental neutron activation analysis, INAA. It is inferred from the multivariate statistical methods that samples from the basin of the Solimoes river and tectonic depression 1 (the most significant of the region) are not significantly different. These results indicate the contribution this river in the sedimentary fill during the evolution in the Quaternary.

Epidemiological snapshot of the mansonelliasis infection in the Amazonian riverine communities in two contiguous municipalities of Solimões river, Amazonas State, Brazil

This study was conducted to gather updated information on the occurrence of Mansonella ozzardi in Codajas, and report new information about filaria found in the riverine communities of Coari, Amazonas State, Brazil. The prevalence (thick blood smear) of infection was 9.4% and 22.0% in Codajas and Coari, respectively. Men (17.1%) had a higher prevalence than women (11.2%) (ANOVA χ2 = -4.93; p = 0.02); and the rates significantly increased with age (ANOVA χ2 = -11.51; p < 0.001) and in certain occupations such as farming/fishing (29.2%) and retired (27.6%). Municipalities located in the Solimoes river have attracted large numbers of migrant workers due to oil and gas exploration in the area, and this may facilitate the spread of filariasis to other non-endemic areas.