Intestinal microbiota perform important functions for the health of fishes. Knowing the microbial composition and evaluating the possible effects caused by anthropogenic pollution in the intestinal microbiota of fish populations might represent an important step in defining microbial biomarkers for water pollution. This study evaluated the impact of environmental contamination on the gut microbiota of the livebearer killifish Phalloceros caudimaculatus. The 16S survey using the V4 region of the 16S rRNA gene was used to characterize and compare the microbiota of two P. caudimaculatus populations from streams with different levels of environmental contamination in Rio Grande, RS, Brazil. Twelve bacterial operational taxonomic units (OTUs) (around one-third of the total) were shared between both fish populations. They represent the core microbiota of the gut in this species. The dominant phyla were Protebacteria and Firmicutes, with more than 80% of relative abundance. The dominant genus was Burkholderia with more than 35% of the relative abundance irrespective of the environmental condition. We detected a lower microbial diversity (Shannon index and observed OTUs) in fish from the polluted stream compared to the reference stream. The PERMANOVA analysis showed that the intestinal microbial communities from fish living in the polluted stream were distinct from those found in the reference stream (p < 0.05). Finally, we identified Luteolibacter, Methylocaldum and Rhodobacter genera, which correlated strongly with the polluted stream. These taxa might represent potential microbial biomarkers of exposure to environmental contaminants in the guts of fish. Confirmation of these findings in other polluted environments might allow the development of a microbiota-based screening approach for environmental evaluation in ecotoxicological studies in aquatic ecosystems.

The contamination of aquatic environments by microplastic has become a major threat to biodiversity. The presence of microplastic is documented in the aquatic fauna of the oceans, but, in the Amazon basin, reports on microplastic occurrence are few. The present study surveyed microplastic occurrence in fishes in an area of the Peruvian Amazon. We sampled 61 specimens of 15 commercial species from local markets in the city of Iquitos, Loreto Department. We detected a total of 2337 microplastic particles, 1096 in the gills and 1241 in the internal organs (esophagus, stomach, intestine, liver, gonads, pancreas, swim bladder and heart). The prevalence of microplastic particles was 100% and the overall average abundance was of 38.3 particles per individual (17.9 particles per individual in gills and 20.3 particles per individual in internal organs). Most particles were found in carnivorous fish. There was no correlation of particle abundance with fish standard length and weight. These results provided evidence of the degree of microplastic contamination of the fish fauna in the region of Iquitos.

Se analizaron la composición, distribución y abundancia de organismos fitoplanctónicos colectados en los periodos de creciente y vaciante del año 2012, en siete estaciones de colecta en la cuenca de los ríos Napo, Arabela y Curaray. En total fueron colectadas 70 muestras de agua (28 muestras para análisis cuantitativo y 42 muestras para análisis cualitativo) que fueron conservadas en formol al 5%. El análisis cualitativo muestra un total de 72 especies de microalgas, distribuidas en 45 géneros, 25 familias y 7 divisiones. El análisis cuantitativo indica que tanto la riqueza específica como la densidad fitoplanctónica fueron mayores en el periodo de creciente (52 especies, y 22,200 individuos.l-1) que en vaciante (41 especies, y 8,800 individuos.l-1). En ambos periodos, las Bacillariophytas fueron las algas predominantes entre las divisiones presentes con 12 000 individuos.l-1. La composición y concentración de fitoplancton en estos cuerpos de agua nos permite concluir que estos ambientes presentan condiciones normales, debido a que aún están presentes los organismos del primer eslabón de la cadena trófica.

RESUMENSe presenta información sobre la evaluación del recurso pesquero registrada en siete estaciones de muestreo ubicadas en los ríos Curaray, Arabela y Napo, durante el período de creciente y vaciante del 2012. El río Curaray presentó el mayor índice de abundancia de peces en ambos períodos, variando de 1,49 kg/hora en el período de creciente a 5,77 kg/hora en el período de vaciante. El índice de abundancia mostró variación entre un sector y otro, siendo marcadamente mayor en Arica (C1) con 2,75 Kg/horas, seguido de Urbina (C2) con 1,54 Kg/horas y Shapajal (C3) con 1,47 Kg/horas, sectores pertenecientes a la cuenca del Curaray. La abundancia de peces mostró diferencias en relación a la composición de peces capturados entre los ciclos hidrológicos de vaciante y creciente en los ríos evaluados. Durante la época de creciente en el Curaray, Triportheus angulatus fue la especie más abundante, mientras que en época de vaciante fue Hemiodus microlepis. Los peces capturados en los ríos Arabela y Curaray registraron tallas mayores a las del río Napo, como es el caso de Triportheus angulatus y Psectrogaster amazónica, especies que alcanzaron tallas promedio de 18,4 cm (Curaray) y 17,8 cm (Arabela).La pesca realizada por la población ribereña encuestada y asentada en las márgenes de los ríos Curaray, Arabela y Napo es considerada como artesanal o de subsistencia.PALABRAS CLAVE: Índice de abundancia, CPUE, composición de tamaños, río Napo, Amazonía peruana. FISHERY RESOURCES AND FISHING IN THE CURARAY, ARABELA AND NAPO RIVERS (PERUVIAN AMAZON) ABSTRACTInformation is presented on the evaluation of fish resources collected in seven sampling stations located in the Curaray, Arabela and Napo rivers, during periods of high and low the 2012. The Curaray index had the highest abundance of fish in both periods, ranging from 1.49 kg/hora in the period increased to 5.77 kg/hour during the dry season. The abundance index showed variations from one sector to another, being markedly increased in Arica (C1) with 2.75 Kg/hour, followed by Urbina (C2) with 1.54 Kg/hour and Shapajal (C3) with 1.47 Kg/ hour sectors within the basin Curaray. The abundance of fish showed differences in the composition of fish caught between hydrological cycles and growing in rivers assessed. In Curaray during the growing season, Triportheus angulatus was the most abundant species, in dry season Hemiodus microlepis was the most abundant. Fish caught in Arabela and Curaray recorded larger sizes to those caught in the Napo River, as is the case Triportheus angulatus and Psectrogaster Amazon who reached average size of 18.4 cm (Curaray) and 17.8 cm (Arabella). Fishing by the surveyed population and settled in riparian margins Curaray, Arabela and Napo rivers (height of the mouth with Curaray) is artisanal or subsistence.

RESUMENSe presentan los resultados de la evaluación ictiológica realizada en los ríos Arabela y Curaray (tributarios del río Napo), durante los periodos hidrológicos de creciente y vaciante del año 2012. Se realizaron pescas exploratorias en siete estaciones de muestreo, utilizando redes trampa de abertura de malla de 2, 3 y 4 pulgadas, con un esfuerzo de pesca de 18 horas por estación. La captura de peces pequeños fue realizada con una red de arrastre de abertura de malla de 1cm (cinco lances por estación). En total se colectaron 4,773 ejemplares, pertenecientes a 240 especies, 136 géneros, 35 familias y 10 órdenes. Durante el periodo de creciente fue registrada la mayor riqueza específica (174 especies), en tanto que en vaciante solo se registraron 153 especies. Los Characiformes fueron el grupo más abundante, con 105 especies en creciente y 79 en vaciante. La mayor riqueza de especies en vaciante se registró en la estación Curaray-3 (74 especies), mientras que en creciente se registró en Arabela-1 (63 especies). La mayor abundancia de peces en vaciante se registró en la estación Arabela-1, (645 ejemplares), en tanto que en la creciente se registró en Curaray-3 (585 ejemplares). Los valores más altos del índice de diversidad de Shannon-Wiener (H') se registraron en las estaciones Curaray-1 (creciente) y Curaray-2 (vaciante). Los resultados de riqueza específica e índice de diversidad nos permiten afirmar que esta cuenca presenta patrones normales de conservación de los stocks pesqueros comparable a las registradas en otras cuencas hidrográficas semejantes.PALABRAS CLAVE: ictiofauna, abundancia, diversidad, estacionalidad, Amazonía peruana. FISH DIVERSITY IN THE ARABELA AND CURARAY RIVERS (NAPO RIVER BASIN) DURING THE 2012 HYDROLOGICAL GROWING AND DRY SEASON, PERUVIAN AMAZON ABSTRACTThis study reports the results of fish abundance and diversity assessment in the Arabela and Curaray rivers, both tributaries of the Napo River Basin for the hydrological growing (flood) and dry season of 2012. Fishing operations were performed on seven sampling stations , using trap nets to catch fish medium to larger size (fishing effort of 18 hours per sampling station ) and type alevinera trawl for catching small fish ( five sets per station) . A total of 4,773 specimens were collected, including a total of 240 species, 136 genera, 35 families and 10 orders. During the flood or growing season were recorded 174 species, 111 genera, 33 families and nine orders, while in the dry season 153 species, 112 genera, 30 families in 10 orders were recorded. The most representative both growing and dry season were Characiforms, with 105 and 79 species, followed Siluriforms, with respectively 75 and 35 species groups. In dry season the highest species richness was recorded in station -3 Curaray (74 species), while in the flood or growing season in Arabela-1 (63 species). The greater abundance of fish found in the dry Arabela-1 season (645 specimens), while increasingly was recorded in Curaray-3 (585 specimens). The highest values of diversit...