Influence of urbanization on stream fish assemblages in three microbasins in the Upper Paraná River Basin / Influência da urbanização em assembleias de peixes de riachos em três microbacias na bacia do Alto Rio Paraná

Abstract The colonization pattern of fish assemblages in streams is often studied in the context of environmental filters. On the other hand, when fish assemblages are subjected to anthropogenic effects, variables associated with environmental quality assume more importance. Therefore, this work evaluated the richness and composition of fish from streams sampled at different urbanization levels, aiming to determine any direct effects on the structure of fish assemblages. To accomplish this, samples were collected from 2003 to 2011 at 31 sites distributed among 3 microbasins in the Rio Ivinhema Basin, Alto Rio Paraná. Based on environmental variables, physicochemical of the water and analysis of the use and occupation of the soil, the microbasins were classified into different urbanization levels (low, medium and high). A total of 4,320 individuals were sampled, out of which 57 fish species were recorded. Sampled sites with medium urbanization level presented higher richness compared to sampled sites with high urbanization level which presented lower richness. Species richness in these sites was explained mainly by water temperature and water velocity. Results confirmed that urbanization does directly affect environmental integrity, which, in turn, can lead to the homogenization of stream assemblages.

Resumo Estudos sobre assembleias de peixes em riachos enfatizam o papel dos filtros ambientais associados ao padrão de colonização das assembleias, por outro lado, quando a assembleia está sujeita aos efeitos antropogênicos, as variáveis ambientais associadas à qualidade ambiental assumem maior importância. Dessa forma, o objetivo deste estudo foi analisar a riqueza e a composição de peixes de riachos amostrados em diferentes níveis de urbanização, buscando evidenciar se o efeito reflete diretamente na estrutura das assembleias. As amostragens foram realizadas em 31 locais distribuídos em três microbacias na bacia Rio Ivinhema, Alto Rio Paraná, no período de 2003 a 2011. Com base nas variáveis ambientais, físico-químicos da água e análise do uso e ocupação do solo as microbacias foram classificadas em diferentes níveis de urbanização (baixo, médio e alto). Foram amostrados um total 4.320 indivíduos, dos quais foram registradas 57 espécies de peixes. Os locais amostrados com influência média da urbanização apresentaram maior riqueza de espécies, entretanto, os locais amostrados com alta influência da urbanização apresentaram menor riqueza de espécies. Dessa forma, constatamos que a urbanização influencia diretamente na integridade ambiental, que pode levar a homogeneização das assembleias de riachos.

Influence of urbanization on stream fish assemblages in three microbasins in the Upper Paraná River Basin / Influência da urbanização em assembleias de peixes de riachos em três microbacias na bacia do Alto Rio Paraná

The colonization pattern of fish assemblages in streams is often studied in the context of environmental filters. On the other hand, when fish assemblages are subjected to anthropogenic effects, variables associated with environmental quality assume more importance. Therefore, this work evaluated the richness and composition of fish from streams sampled at different urbanization levels, aiming to determine any direct effects on the structure of fish assemblages. To accomplish this, samples were collected from 2003 to 2011 at 31 sites distributed among 3 microbasins in the Rio Ivinhema Basin, Alto Rio Paraná. Based on environmental variables, physicochemical of the water and analysis of the use and occupation of the soil, the microbasins were classified into different urbanization levels (low, medium and high). A total of 4,320 individuals were sampled, out of which 57 fish species were recorded. Sampled sites with medium urbanization level presented higher richness compared to sampled sites with high urbanization level which presented lower richness. Species richness in these sites was explained mainly by water temperature and water velocity. Results confirmed that urbanization does directly affect environmental integrity, which, in turn, can lead to the homogenization of stream assemblages.

Estudos sobre assembleias de peixes em riachos enfatizam o papel dos filtros ambientais associados ao padrão de colonização das assembleias, por outro lado, quando a assembleia está sujeita aos efeitos antropogênicos, as variáveis ambientais associadas à qualidade ambiental assumem maior importância. Dessa forma, o objetivo deste estudo foi analisar a riqueza e a composição de peixes de riachos amostrados em diferentes níveis de urbanização, buscando evidenciar se o efeito reflete diretamente na estrutura das assembleias. As amostragens foram realizadas em 31 locais distribuídos em três microbacias na bacia Rio Ivinhema, Alto Rio Paraná, no período de 2003 a 2011. Com base nas variáveis ambientais, físico-químicos da água e análise do uso e ocupação do solo as microbacias foram classificadas em diferentes níveis de urbanização (baixo, médio e alto). Foram amostrados um total 4.320 indivíduos, dos quais foram registradas 57 espécies de peixes. Os locais amostrados com influência média da urbanização apresentaram maior riqueza de espécies, entretanto, os locais amostrados com alta influência da urbanização apresentaram menor riqueza de espécies. Dessa forma, constatamos que a urbanização influencia diretamente na integridade ambiental, que pode levar a homogeneização das assembleias de riachos.

Influence of urbanization on stream fish assemblages in three microbasins in the Upper Paraná River Basin

Abstract The colonization pattern of fish assemblages in streams is often studied in the context of environmental filters. On the other hand, when fish assemblages are subjected to anthropogenic effects, variables associated with environmental quality assume more importance. Therefore, this work evaluated the richness and composition of fish from streams sampled at different urbanization levels, aiming to determine any direct effects on the structure of fish assemblages. To accomplish this, samples were collected from 2003 to 2011 at 31 sites distributed among 3 microbasins in the Rio Ivinhema Basin, Alto Rio Paraná. Based on environmental variables, physicochemical of the water and analysis of the use and occupation of the soil, the microbasins were classified into different urbanization levels (low, medium and high). A total of 4,320 individuals were sampled, out of which 57 fish species were recorded. Sampled sites with medium urbanization level presented higher richness compared to sampled sites with high urbanization level which presented lower richness. Species richness in these sites was explained mainly by water temperature and water velocity. Results confirmed that urbanization does directly affect environmental integrity, which, in turn, can lead to the homogenization of stream assemblages.

Resumo Estudos sobre assembleias de peixes em riachos enfatizam o papel dos filtros ambientais associados ao padrão de colonização das assembleias, por outro lado, quando a assembleia está sujeita aos efeitos antropogênicos, as variáveis ambientais associadas à qualidade ambiental assumem maior importância. Dessa forma, o objetivo deste estudo foi analisar a riqueza e a composição de peixes de riachos amostrados em diferentes níveis de urbanização, buscando evidenciar se o efeito reflete diretamente na estrutura das assembleias. As amostragens foram realizadas em 31 locais distribuídos em três microbacias na bacia Rio Ivinhema, Alto Rio Paraná, no período de 2003 a 2011. Com base nas variáveis ambientais, físico-químicos da água e análise do uso e ocupação do solo as microbacias foram classificadas em diferentes níveis de urbanização (baixo, médio e alto). Foram amostrados um total 4.320 indivíduos, dos quais foram registradas 57 espécies de peixes. Os locais amostrados com influência média da urbanização apresentaram maior riqueza de espécies, entretanto, os locais amostrados com alta influência da urbanização apresentaram menor riqueza de espécies. Dessa forma, constatamos que a urbanização influencia diretamente na integridade ambiental, que pode levar a homogeneização das assembleias de riachos.

Temporal patterns of fish occurrence of the euryhaline sector of a subtropical estuary, southern Brazil

Fish fauna was studied in five sites of the shallow infralittoral of the Paranaguá Bay during the period from October 1999 to September 2000. At each sampling site, fish were sampled with other trawls, salinity and temperature were measured, water samples were taken from the bottom of the water column for determination of dissolved oxygen, dissolved inorganic nitrogen and phosphate. The spatial and temporal behavior of the environmental variables was analyzed by a Principal Component Analysis; Cluster Analysis was used to gather the sampling sites, and Factorial Correspondence Analysis was applied to the most abundant species. Temperature was themost important variable for the distribution of the months, allowing the division of the study period into hot and cold months. The temporal variation in the fish fauna composition was indicated by cluster analysis, with highest percentages of dissimilarity between the sampling sites during hot months. The variation in dissimilarity between the sites occurred due to differences in the number of individuals and species of the catches. The high frequencies of occurrence of Anisotremus surinamensis, Etropus crossotus, Genidens genidens, Micropogonias furnieri and Sphoeroides greeleyiwere related to high temperatures. The greatest number of fish and species observed in hot months may be related to the life cycle of many species, which reproduce in warmer months, and whose offspring use estuaries as breeding areas.

Influence of sediment granulometry and salinity on the composition of an estuarine fish assemblage in the Mexican Tropical Pacific / Influencia de la granulometría del sedimento y la salinidad en la composición de una comunidad de peces estuarinos en el Pacífico tropical mexicano

Abstract Barra de Navidad lagoon (BNL) is one of the main coastal wetlands in the coast of the State of Jalisco, Mexico. It is a Ramsar site (wetland of international importance) and has been included among the 81 mangrove sites with biological relevance and ecological rehabilitation needs in Mexico. Although fish fauna composition is well known in BNL, little evidence exists that support seasonal and spatial changes of fish assemblages' structure. The hypothesis tested in this study was that there are significant seasonal and spatial changes in BNL fish assemblages' composition which can be explained, at least partially, by changes in salinity, water temperature and sediment's granulometry. Fish assemblages were sampled monthly from October 2012 to September 2013 at four zones of BNL, using gill nets (7.62 mm stretched mesh). A sample was taken every month in a randomly selected area of each zone. Prior to each sampling operation, water salinity and temperature were measured using an YSI-30 probe. Samples of sediment were collected with a Van Veen grab sampler in three randomly selected points of each zone for granulometry and organic matter analyses. A total of 2 026 individuals belonging to 48 species were collected. Slightly more than 90 % of all caught fish belonged to nine species: Peruvian mojarra (Diapterus brevirostris), Pacific crevalle-jack (Caranx caninus), White mullet (Mugil curema), Blue sea-catfish (Ariopsis guatemalensis), Oval flounder (Syacium ovale), Pacific lined sole (Achirus mazatlanus), Yellowfin mojarra (Gerres simillimus), Pacific bumper (Chloroscombrus orqueta) and Freckled porcupinefish (Diodon holocanthus). Generalized linear models yielded significant differences among zones for the mean abundance of each of these nine species, but only in two cases seasonal differences were significant (D. brevisrostris and C. caninus). Permutational multivariate analysis of variance yielded also significant differences among zones and between seasons for the composition of the fish assemblage. Redundancy analysis using salinity, temperature, and percentage mud in sediment as environmental variables showed that fish assemblage's composition varies along two main gradients defined by mud fraction of sediments in a small spatial scale (~ 3 km) and salinity in a seasonal scale. Percentage of variation explained by canonical axes was less than 25 %, indicating that other factors could be influencing changes in assemblage composition. As most species appear as juveniles in the lagoon, fluctuations in their abundances could be linked, at least partially, with recruitment events. Rev. Biol. Trop. 66(3): 1065-1077. Epub 2018 September 01.

Resumen La laguna Barra de Navidad (LBN) es uno de los principales humedales costeros en la costa del Estado de Jalisco, México. Es un sitio Ramsar (humedal de importancia internacional) y ha sido incluida entre los 81 sitios de manglar con relevancia biológica y necesidades de rehabilitación en México. Aunque la composición de la ictiofauna es bien conocida en LBN, hay poca evidencia sobre la existencia de cambios estacionales y espaciales en la estructura de la misma. La hipótesis que guió este trabajo fue que en la composición de la ictiofauna de la laguna Barra de Navidad hay cambios espaciales y estacionales que pueden ser explicados, al menos parcialmente, por cambios en la salinidad, temperatura del agua y granulometría del sedimento. Los peces fueron muestreados mensualmente de octubre 2012 a septiembre 2013 en cuatro zonas de la laguna, usando redes agalleras (7.62 mm de malla estirada). Se tomó una muestra cada mes en un área seleccionada aleatoriamente en cada zona. Previo a cada operación de muestreo, se midieron la salinidad y la temperatura del agua con una sonda YSI-30. Muestras de sedimento para análisis granulométrico y del contenido de materia orgánica, se recolectaron con una draga tipo Van Veen en tres puntos seleccionados aleatoriamente en cada zona. Se recolectaron 2 026 individuos de 48 especies de peces. Poco más de 90 % de todos los peces contados pertenecieron a nueve especies: Diapterus brevirostris, Caranx caninus, Mugil curema, Ariopsis guatemalensis, Syacium ovale, Achirus mazatlanus, Gerres simillimus, Chloroscombrus orqueta y Diodon holocanthus. Modelos lineales generalizados arrojaron diferencias significativas entre zonas para la abundancia media de estas nueve especies, pero solo en dos casos se encontraron diferencias significativas entre estaciones (D. brevirostris y C. caninus). El análisis multidimensional de varianza basado en permutaciones, arrojó también diferencias significativas entre zonas y entre estaciones para la composición de la ictiofauna. El análisis de redundancia usando la salinidad, la temperatura y el porcentaje de lodo en el sedimento como variables ambientales, mostró que la composición de la ictiofauna varía a lo largo de dos gradientes definidos por la fracción de lodo de los sedimentos en una escala espacial pequeña (~ 3 km) y la salinidad en una escala estacional. El porcentaje de variación explicado por los ejes canónicos fue menor de 25 %, indicando que otros factores pudieran influir en los cambios de la composición de la ictiofauna. Como la mayoría de las especies aparecen en su estadio juvenil en la laguna, las fluctuaciones en sus abundancias pudieran estar relacionadas, al menos parcialmente, con eventos de reclutamiento.

Fish beta diversity responses to environmental heterogeneity and flood pulses are different according to reproductive guild

In floodplain communities, beta diversity is influenced by different factors; however, environmental heterogeneity and floods are believed to be particularly influential. The influence of environmental heterogeneity and floods on beta diversity may vary among guilds that present different ecological traits. This study evaluated the correlation between the environmental heterogeneity and flood periods and the beta diversity of trophic and reproductive guilds of fish assemblages. Sampling was conducted quarterly between 2000 and 2012 in the upper Paraná River floodplain. The environmental heterogeneity and period (i.e., dry or flood) were associated with the beta diversity of each guild based on the results of generalized least squares linear models. Only guilds with parental care were influenced by the interaction between environmental heterogeneity and period. The beta diversity of the other guilds presented no relationship between environmental heterogeneity and period. It is likely that species with parental care presented less dispersal capacity, which increased the dissimilarity among assemblages. The higher dispersion rates of the other guilds may be responsible for the lack of relationship between the beta diversity and the environmental heterogeneity and period. In sum, these results suggest that reproductive guilds influence how environmental heterogeneity and floods affect beta diversity variation.(AU)

A diversidade beta é influenciada por diferentes fatores em comunidades de planícies de inundação; contudo, acredita-se que a heterogeneidade ambiental e inundações sejam particularmente influentes. A influência da heterogeneidade ambiental e inundações na diversidade beta podem variar entre guildas que apresentam diferentes características ecológicas. Este estudo avaliou a correlação entre heterogeneidade ambiental, os períodos de inundação e a diversidade beta de guildas tróficas e reprodutivas de peixes. A amostragem foi realizada trimestralmente entre 2000 e 2012 na planície de inundação do Alto rio Paraná. Heterogeneidade ambiental e o período (i.e., seca ou cheia) foram associados à diversidade beta de cada guilda por modelos lineares de quadrados mínimos generalizados. Somente guildas com cuidados parentais foram influenciadas pela interação entre heterogeneidade ambiental e período. A diversidade beta das outras guildas não apresentou relação com heterogeneidade ambiental e período. É provável que espécies com cuidados parentais apresentem menor capacidade de dispersão, o que aumenta a diferença entre as assembleias. As maiores taxas de dispersão de outras guildas podem ser responsáveis pela ausência de relação entre a diversidade beta e heterogeneidade ambiental e o período. Em suma, os resultados sugerem que as guildas reprodutivas influenciam a forma como a heterogeneidade ambiental e as inundações afetam a variação da diversidade beta.(AU)

The influence of habitat structure on fish assemblages in Amazonian streams of Machado river basin / Influencia de la estructura del hábitat en el ensamble de comunidades de peces en ríos de la cuenca amazónica Machado

Abstract:Igarapés are Amazonian streams that are extremely susceptible to environmental changes. Due to the rapidly occurring riparian land use changes, and the several impacts these may have on fish assemblages, it is highly valuable to describe and understand the current relationships between these assemblages and the local environmental conditions, especially in barely know areas. In this research, we studied the taxonomic composition and fish assemblage attributes variation in three streams with different riparian conservation conditions: forest, intermediate and pasture. Samplings were performed every two months from October 2011 to September 2012, in three 1st order streams in the Machado River Basin, Rondônia. Fish were collected using trawls (seine net with a mesh size of 2 mm) and dip nets (2 mm mesh) along the entire stretch; the obtained samples were preserved and identified per site type. A total of 2 141 fish specimens belonging to 59 species, 17 families and five orders were recorded. Unlike the intermediate and pasture streams, the forest stream showed a high richness and low abundance. The forested stream exhibited the highest diversity and evenness value, and had low dominance, unlike the other streams. The variance partitioning and partial Redundancy Analysis (pRDA) indicated that assemblage composition was significantly explained by the environmental variables such as: depth, water velocity, pteridophytes and grasses, but not by spatial predictors. The non-metric multidimensional scaling (NMDS) analysis showed that intermediate and pasture streams separated from the forested stream. We concluded that both, the stream environmental variables and fish assemblage attributes were influenced by the different conservation status and land cover. Given the influence of regional processes, which have a pervasive role in local fish assemblages, land use at the watershed scale is important, especially to explain the higher richness and diversity found in forested streams. Rev. Biol. Trop. 65 (1): 103-115. Epub 2017 March 01.

ResumenIgarapés son ríos amazónicos extremadamente susceptibles a los impactos ambientales. Debido al impacto de los cambios en el uso de las zonas riparias en los ensambles de peces, es importante describir y entender las relaciones entre los ensambles de peces y los factores ambientales, especialmente en áreas poco conocidas. Se estudió la composición taxonómica y los atributos del ensamble de peces en ríos bajo diferentes condiciones de conservación de la zona riparia: bosque, zona intermedia y pastos. Los muestreos se realizaron cada dos meses entre Octubre 2011 y Septiembre 2012, en tres ríos de primer orden en la cuenca del río Machado, Rondonia. Los peces fueron recolectados con redes de cerco y de profundidad (2 mm) a lo largo de todo el tramo. Se registró un total de 2 141 ejemplares pertenecientes a 59 especies, 17 familias y 5 órdenes. A diferencia de la zona intermedia y pasto, el bosque mostró una alta riqueza y baja abundancia. El área boscosa exhibió el valor más alto de diversidad y uniformidad, y baja dominancia, a diferencia de los otros sitios. La varianza particionada y el análisis de redundancia parcial (pRDA) indicaron que la composición del ensamble fue significativamente explicado por las variables ambientales como: profundidad, velocidad del agua, pteridofitas y pastos, pero no por predictores espaciales. El análisis de escalamiento multidimensional no métrico (EMNM) mostró que los ríos de sitios intermedios y pastos estaban separados de los ríos del bosque. Llegamos a la conclusión de que las variables ambientales de los ríos y los atributos del ensamble de peces se ven influenciados por los diferentes niveles de conservación y cobertura del suelo. En vista de la influencia de los procesos regionales en el ensamble de peces locales, el uso del suelo a escala de cuenca es importante, especialmente para explicar la alta riqueza y diversidad que se encuentra en el los ríos del área boscosa.

The protected areas system in Brazil as a baseline condition for wetlands management and fish conservancy: the example of the Pantanal National Park

Considering the need for the Brazilian government to develop tools for environmental monitoring for biodiversity conservancy purposes in the national protected areas system, this paper focuses on determining reference site metrics (or baselines) for adapting the Index of Biotic Integrity (IBI) based on the fish assemblages in the Pantanal National Park (PNP). The habitats in the PNP were grouped into four categories: main rivers, corixos (channels connecting the floodplain), permanent bays, and temporary bays. Fish samplings were performed at 12 points during the dry season (Oct-Nov 2010 and 2011). 146 fish species were identified from the total 18,954 individuals collected with standardized fishing gear. There was no association between the structure of the fish assemblage and categories, suggesting a theory on homogeneity of habitats. The final IBIPNP consists of nine metrics, most of them were framed in excellent class, some in fair, and none in poor. There was no significant difference in IBIPNP scores between the two sampled years. This approach provides a direct application for wetland management purposes.(AU)

É iminente que o Brasil desenvolva ferramentas para monitorar o sistema de áreas protegidas do país, formado especialmente pelas Unidades de Conservação e tendo como foco a proteção efetiva da biodiversidade. Nesse contexto, esse trabalho discute métricas de referência (ou linhas de base) para compor um Índice de Integridade Biótica (IIB) baseado nas comunidades de peixes, tendo como área de estudo o Parque Nacional do Pantanal Matogrossense. Os hábitats encontrados no Parque foram agrupados em quatro estratos ambientais: rios, corixos (cursos d´água que se conectam à planície de inundação) e baías permanentes e temporárias. As coletas de peixes foram realizadas em 12 pontos amostrais durante o período seco (out/nov de 2010 e 2011). Foram identificadas 146 espécies de peixes, totalizando 18.954 exemplares coletados em amostragens padronizadas. Não houve associação entre a estrutura da comunidade e os estratos ambientais, sugerindo homogeneidade de hábitats. O IIB final foi composto por nove métricas, a maior parte alocada na classe excelente de integridade biótica, poucas na classe regular e nenhuma na classe pobre. Não houve diferença significativa no IIB entre os dois anos consecutivos. Esses resultados oferecem subsídios técnicos para a tomada de decisão sobre a gestão das áreas alagáveis no Pantanal brasileiro.(AU)

Influence of environmental variables on stream fish fauna at multiple spatial scales

Effects of environmental variables at different spatial scales on freshwater fish assemblages are relatively unexplored in Neotropical ecosystems. However, those influences are important for developing management strategies to conserve fish diversity and water resources. We evaluated the influences of site- (in-stream) and catchment-scale (land use and cover) environmental variables on the abundance and occurrence of fish species in streams of the Upper Araguari River basin through use of variance partitioning with partial CCA. We sampled 38 1st to 3rd order stream sites in September 2009. We quantified site variables to calculate 11 physical habitat metrics and mapped catchment land use/cover. Site and catchment variables explained > 50% of the total variation in fish species. Site variables (fish abundance: 25.31%; occurrence: 24.51%) explained slightly more variation in fish species than catchment land use/cover (abundance: 22.69%; occurrence: 18.90%), indicating that factors at both scales are important. Because anthropogenic pressures at site and catchment scales both affect stream fish in the Upper Araguari River basin, both must be considered jointly to apply conservation strategies in an efficient manner.(AU)

Os efeitos das variáveis ambientais em diferentes escalas espaciais sobre as assembleias de peixes de água doce ainda é um tema pouco explorado na região Neotropical. Entretanto é um assunto de extrema relevância, pois gera subsídios para definições de estratégias de manejo e conservação de ictiofauna e dos recursos hídricos. Nós avaliamos a influência de variáveis ambientais em escalas local (dentro do rio) e da paisagem (uso e cobertura do solo) na abundância e ocorrência das espécies de peixes de riachos da bacia do alto rio Araguari através da partição da variância usando CCA parcial. Um total de 38 riachos de até 3ª ordem foi amostrado em setembro de 2009. Nós quantificamos variáveis locais para calcular 11 métricas de hábitats físicos e mapeamos o uso e cobertura do solo. O conjunto de dados (variáveis locais e da paisagem) explicou mais de 50% da variação total nas espécies de peixes. Variáveis em escala local (abundância: 25,31%; ocorrência: 24,51%) explicaram levemente uma maior variação nas assembleias de peixes do que o uso e cobertura do solo (abundância: 22,69%; ocorrência: 18,90%), indicando que os fatores em ambas as escalas de estudo são importantes. Uma vez que a influência antrópica em diferentes escalas afeta as espécies de peixes em riachos da bacia do alto rio Araguari, ambas devem ser consideradas juntamente para a adoção de estratégias de conservação de uma forma racional.(AU)

Development of habitat suitability criteria for Neotropical stream fishes and an assessment of their transferability to streams with different conservation status

We assessed the preference of 10 fish species for depth and velocity conditions in forested streams from southeastern Brazil using habitat suitability criteria (HSC curves). We also tested whether preference patterns observed in forested streams can be transferred to deforested streams. We used data from fish sampled in 62 five-meter sites in three forested streams to construct preference curves. Astyanax altiparanae, A. fasciatus, Knodus moenkhausii, and Piabina argentea showed a preference for deep slow habitats, whereas Aspidoras fuscoguttatus, Characidium zebra, Cetopsorhamdia iheringi, Pseudopimelodus pulcher, and Hypostomus nigromaculatus showed an opposite pattern: preference for shallow fast habitats. Hypostomus ancistroides showed a multimodal pattern of preference for depth and velocity. To evaluate whether patterns observed in forested streams may be transferred to deforested streams, we sampled 64 five-meters sites in three deforested streams using the same methodology. The preference for velocity was more consistent than for depth, as success in the transferability criterion was 86% and 29% of species, respectively. This indicates that velocity is a good predictor of species abundance in streams, regardless of their condition.

Neste estudo avaliamos a preferência de 10 espécies de peixes por condições de profundidade e fluxo em riachos florestados do sudeste do Brasil por meio do critério de adequabilidade de habitat (habitat suitability criteria - curvas HSC). Testamos também se os padrões de preferência observados nos riachos florestados podem ser transferidos para riachos desmatados. Foram realizadas amostragens da ictiofauna em 62 trechos de cinco metros de extensão em três riachos florestados para a construção das curvas de preferência. Astyanax altiparanae, A. fasciatus, Knodus moenkhausii e Piabina argentea apresentaram preferência por habitats lentos e profundos, enquanto Aspidoras fuscoguttatus, Characidium zebra, Cetopsorhamdia iheringi, Pseudopimelodus pulcher e Hypostomus nigromaculatus apresentaram um padrão oposto de preferência por habitats rasos e de fluxo rápido. Hypostomus ancistroides apresentou um padrão de preferência por profundidade e fluxo multimodal. Para avaliar se os padrões observados nos riachos florestados podem ser transferidos para riachos desmatados foram realizadas amostragens da ictiofauna em 64 trechos de cinco metros de extensão em três riachos desmatados utilizando a mesma metodologia aplicada aos riachos florestados. O sucesso na transferência do critério foi de 86% e 29% para fluxo e profundidade, ou seja, a preferência por fluxo foi mais consistente do que por profundidade. Isso indica que o fluxo é um bom preditor da abundância das espécies em riachos, independentemente do seu estado de conservação.

Second floor, please: the fish fauna of floating litter banks in Amazonian streams and rivers

Floating litter banks are an ephemeral habitat consisting of branches, twigs, flowers, seeds, and fruits that are trapped on the stream water surface by a variety of retention mechanisms. These heterogeneous materials form a deep layer of dead plant matter that is colonized by a variety of organisms, including fish that forage on the aquatic macroinvertebrates found in this unique habitat. In this study, we aimed to characterize which fish species occupy the floating litter banks and their trophic characteristics, as well as determine if fish assemblage composition and species richness can be predicted by the size of the floating litter banks. Fish sampling was conducted in five rivers located in the Amazon basin. Of the 31 floating litter banks sampled that contained fish, 455 individuals were recorded and were distributed within 40 species, 15 families and five orders. Siluriformes were the most representative order among the samples and contained the largest number of families and species. The fish fauna sampled was mainly composed of carnivorous species that are typically found in submerged litter banks of Amazonian streams. The fish assemblage composition in the kinon can be predicted by the volume of the floating litter banks using both presence/absence and abundance data, but not its species richness. In conclusion, kinon banks harbor a rich fish assemblage that utilizes this habitat for shelter and feeding, and may function as a refuge for the fishes during the peak of the flooding season.

Bancos de folhiço flutuantes são habitats efêmeros constituídos de troncos e galhos de árvores, flores, sementes e frutos retidos por uma variedade de mecanismos. Estes materiais formam uma camada espessa de matéria vegetal morta, que é colonizada por diferentes organismos, incluindo peixes que se alimentam de macroinvertebrados aquáticos presentes neste habitat. Nosso objetivo foi caracterizar as espécies e características tróficas dos peixes que ocupam esses bancos de folhiço flutuantes, bem como determinar se a composição da assembleia de peixes e a riqueza de espécies podem ser previstas pelo tamanho dos bancos. A amostragem dos peixes foi realizada em cinco rios da bacia amazônica. Dos 31 bancos de folhiço flutuantes amostrados que continham peixes, foram registrados 455 indivíduos distribuídos em 40 espécies, 15 famílias e cinco ordens. Siluriformes foi a ordem mais representativa, com o maior número de espécies e famílias. A fauna de peixes coletados foi composta principalmente por espécies carnívoras, que geralmente são encontrados em bancos de folhiço submersos de igarapés amazônicos. A composição das assembleias de peixes do 'kinon' pode ser prevista pelo volume desses bancos de liteira flutuante, tanto utilizando dados de presença/ausência quanto de abundância, mas não de riqueza de espécies. Em conclusão, os bancos de folhiço flutuante abrigam uma rica assembleia de peixes, que utilizam esse habitat como local de abrigo e de alimentação, e podem funcionar como refúgio para a ictiofauna dos bancos de folhiço submerso durante a estação chuvosa.

Deepwater fish assemblages at Isla del Coco National Park and Las Gemelas Seamount, Costa Rica / Conjuntos de peces de aguas profundas en el Parque Nacional Isla del Coco y el Monte Submarino Las Gemelas, Costa Rica

The deepwater faunas of oceanic islands and seamounts of the Eastern Tropical Pacific are poorly known. From 11-22 September 2009 we conducted an exploration of the deepwater areas of the Isla del Coco Marine Conservation Area, Costa Rica and a nearby seamount using a manned submersible. The goal of the exploration was to characterize the habitats and biota, and conduct quantitative surveys of the deepwater portions of Isla del Coco National Park and Las Gemelas Seamount, located about 50km southwest of Isla del Coco. We completed a total of 22 submersible dives, spanning more than 80hr underwater, and collected a total of 36hr of video. We surveyed habitats from 50-402m and observed more than 45 species of fishes, some of which have not yet been described and are likely new to science. The diversity of fish species in deep water at Isla del Coco National Park was lower than the diversity of fishes in shallow water, and eight species groups accounted for more than 95% of the total fish biomass. The combined density of all fish species was higher at Las Gemelas Seamount (253 fishes/100m²) than at Isla del Coco National Park (138 fishes/100m²). The combined density of fishes in habitats comprised primarily of bedrock or large boulders outcrops was more than three times as high at Las Gemelas Seamount as it was at Isla del Coco National Park. This discrepancy was caused by the extremely high concentration of Anthiinae fishes in rocky habitats at Las Gemelas Seamount. Densities of fishes in the other habitats were similar between the two sites. Similarly, when estimates of fish density were plotted by slope categories the density was much greater on steep slopes, which were usually comprised of rock habitats. Also, the density of fishes was greatest on high rugosity habitats. Results of these submersible surveys indicate that seamounts in the tropical eastern Pacific Ocean may be an important source of biodiversity and that more quantitative surveys are needed to characterize the fauna of the region.

Las faunas de aguas profundas de islas oceánicas del Pacífico Tropical Oriental se conocen poco y de los montes submarinos nada. Del 11 al 22 de septiembre de 2009 llevamos a cabo una exploración de zonas profundos del Área de Conservación Marina Isla del Coco utilizando un submarino tripulado. El objetivo del estudio fue caracterizar los hábitats y las comunidades, y cuantificar las poblaciones de peces de profundidad en la Isla del Coco y los montes submarinos Las Gemelas, situados a 50km al suroeste de la Isla del Coco. Realizamos 22 inmersiones con el submarino, con más de 80 horas de observación submarina, y filmamos 30 horas de video. Investigamos hábitats entre 50-402m de profundidad y observamos más de 45 especies de peces, algunas de las cuales son especies nuevas para la ciencia. La diversidad de peces profundos en la Isla del Coco fue menor que en aguas someras, y ocho grupos de especies representaron más del 95% de la biomasa total de peces. La densidad combinada de peces fue 253 peces/100m² en Las Gemelas y 138 peces/100m² en la Isla del Coco.

Influence of watershed activities on the water quality and fish assemblages of a tropical African reservoir

Agricultural and fisheries activities around the watershed of an African tropical reservoir (Oyun reservoir, Offa, Nigeria) were found to contribute significantly to water quality deterioration of the dam axis of the reservoir, leading to eutrophication of that part of the reservoir. This is evident from the high amount of nitrate (6.4 mg/l), phosphate (2.2 mg/l) and sulphate (16.9 mg/l) in the water body which was higher than most other reservoirs in Nigeria. These nutrients originate in fertilizer run-offs from nearby farmlands and were found in higher concentrations in the rainy season which is usually the peak of agricultural activities in the locality. The eutrophication was more pronounced on the dam axis because it is the point of greatest human contact where pressure and run-off of sediments were high. The eutrophication altered the food web cycle which consequently affected the fish species composition and abundance with the dominance of cichlids (planktivorous group) and decline of some species in the fish population. Best management practices (BMP) to control and reduce the eutrophication and improve water quality and fish assemblages should be adopted and adapted to suit the situation in the reservoir. Rev. Biol. Trop. 57 (3): 707-719. Epub 2009 September 30.

Las actividades agrícolas y pesqueras que se desarrollan alrededor del embalse tropical africano de Oyun, Offa, Nigeria, contribuyen de forma significativa al deterioro de la calidad del agua, provocando eutroficación. Esto es evidente a partir de la gran cantidad de nitrato (6.4 mg / l), fosfato (2.2 mg / l) y sulfato (16.9 mg / l), si se compara con otros embalses de Nigeria. Estos nutrientes proceden de fertilizantes utilizados en áreas agrícolas y las concentraciones aumentan en la estación lluviosa cuando aumentan las actividades agrícolas en la zona. La eutroficación es más pronunciada donde existe mayor actividad humana, y altera la cadena trófica y en consecuencia, la composición íctica, con predominio de los cíclidos y disminución de otros peces. Se requiere manejo de la cuenca para reducir la eutrofización y mejorar la calidad del agua y los peces.

Natural and human-induced variability in the composition of fish assemblages in the Northwestern Cuban shelf

The main goal of the study was to obtain field data to build a baseline of fish assemblage composition that can be used comparatively for future analyses of the impact of human actions in the region. A basic network of 68 sampling stations was defined for the entire region (4 050 km2). Fish assemblage species and size composition was estimated using visual census methods at three different spatial scales: a) entire region, b) inside the main reef area and c) along a human impact coastal gradient. Multivariate numerical analyses revealed habitat type as the main factor inducing spatial variability of fish community composition, while the level of human impact appears to play the main role in fish assemblage composition changes along the coast. A trend of decreasing fish size toward the east supports the theory of more severe human impact due to overfishing and higher urban pollution in that direction. This is the first detailed study along the northwest coast of Cuba that focuses on fish community structure and the natural and human-induced variations at different spatial scales for the entire NW shelf. This research also provides input for a more comprehensive understanding of coastal marine fish communities’ status in the Gulf of Mexico basin. Rev. Biol. Trop. 57 (3): 721-740. Epub 2009 September 30.

Se obtuvieron datos de campo para una línea base de la composición de la ictiofauna que pueda ser usada comparativamente para el análisis de impactos humanos futuros en la región. Se estableció una red básica de 68 estaciones de muestreo para la región completa (4 050 km2). La composición por especies y por tallas de la ictiofauna fue estimada utilizando métodos de censo visual en tres escalas espaciales diferentes: a) La región completa, b) dentro del área principal de arrecifes y c) a lo largo de un gradiente costero de impacto humano. El tipo de hábitat es el factor principal que induce la variación espacial en la composición de la ictiofauna, mientras que el impacto humano juega el papel principal en los cambios a lo largo de la costa. La tendencia de la talla de los peces a disminuir hacia el este da soporte a la idea de un impacto humano más severo en esa dirección, debido a la sobrepesca y la contaminación. Este es el primer estudio detallado a lo largo de la costa NW de Cuba que se enfoca a la estructura de la comunidad de peces y sus variaciones naturales o antropogénicas en escalas espaciales diferentes.

Ictiofauna de sistemas cárstico-palustres con impacto antrópico: los petenes de Campeche, México

Ichthyofauna of karstic wetlands under anthropic impact: the "petenes" of Campeche, Mexico. "Petenes" are small springs and associated streams that drain into wetlands near the coast in karstic areas. We studied composition, distribution, and abundance of the ichthyofauna in Los Petenes region (northwest Campeche). Two petenes displaying different degrees and types of anthropic impact were selected, Hampolol and El Remate. Hampolol has a smaller area but a longer derived stream; it is located within a protected area, but has been invaded by tilapia. El Remate is a popular spa, with no tilapia; it has a larger area but a shorter derived stream. At each "petén", several sites in the main spring, the associated stream, and secondary (temporary) springs were sampled in the rainy and dry seasons. Fishing gear was variable (throw net, gill net, small and large seine nets), but effort was uniform. We recorded temperature, dissolved oxygen, salinity, and depth at each site and season; also, we noted the different types and intensities of anthropic impact (channelization, presence of exotic species, recreational use, etc.) at each petén. We compared the petenes in terms of their environmental quality and fish fauna (composition, distribution, abundance, biomass); we also tested for effects of season and site within each petén. The study found 27 species of fishes, included in 18 genera and eight families, 24 species in Hampolol and 20 in El Remate. The geographical range of ‘Cichlasoma’ salvini, Rivulus tenuis, Phallichthys fairweatheri, Xiphophorus hellerii, and X. maculatus is extended. The dominant species in both seasons was Astyanax (probable hybrids A. aeneus × altior at Hampolol, pure A. altior at El Remate), which contributed most of the abundance and biomass, together with Vieja synspila and Poecilia velifera. A significantly greater overall diversity (H’n=3.31) was recorded in Hampolol compared to El Remate (H’n=2.10). Cluster analysis of sites by species presence allowed distinction of two groupings within each petén: permanent waters (i.e., main spring, stream) vs. temporary sites (secondary springs, which dry out in winter). Environmental parameters (except salinity) presented significant differences by site and season; a canonical correspondence analysis indicated that the distribution of fish assemblages was influenced by the environmental parameters in both seasons. In terms of composition, historical factors play a role in the differences between the fish assemblages of the two petenes, especially concerning the presence of Astyanax hybrids and Xiphophorus spp. in the southern petén (Hampolol) and Poecilia velifera in the northern petén (El Remate). Rev. Biol. Trop. 57 (1-2): 141-157. Epub 2009 June 30.

Los petenes son pequeños manantiales y arroyos asociados que drenan a sistemas palustres en áreas cársticas costeras. Se estudió la composición, distribución y abundancia de la ictiofauna en dos petenes del noroeste de Campeche, en el manantial principal, el arroyo asociado, y pequeños ojos de agua secundarios (temporales), en dos épocas del año. Se registraron variables ambientales y tipos de impacto antrópico en cada petén. Se encontraron en total 27 especies de peces, con extensiones de ámbito de ‘Cichlasoma’ salvini, Rivulus tenuis, Phallichthys fairweatheri, Xiphophorus hellerii y X. maculatus. La especie dominante en ambas épocas fue Astyanax (probables híbridos A. aeneus × altior en Hampolol, A. altior en El Remate). Hubo diferencia significativa en diversidad entre ambos petenes. El análisis de conglomerados diferenció dos agrupaciones dentro de cada petén: aguas permanentes y sitios temporales. Las variables ambientales (excepto salinidad) presentaron diferencias significativas por sitio y época; un análisis de correspondencia canónica indicó que la distribución de los conjuntos de peces tuvo influencia de las variables ambientales en ambas temporadas. En términos de composición, los factores históricos juegan un papel en las diferencias ictiológicas entre ambos petenes, sobre todo por lo que concierne a la presencia de híbridos de Astyanax, así como Xiphophorus hellerii en el petén del sur (Hampolol) y de Poecilia velifera en el petén del norte (El Remate).

Variação espacial e temporal nas assembléias de peixes de riachos na bacia do rio Guiraí, Alto Rio Paraná / Spatial and temporal variation in stream fish assemblages of Guiraí River Basin, Upper Paraná Basin

This paper aims to characterize the fish assemblages and to quantify the importance of spatial and temporal variations on the organization of stream fish assemblages of Guiraí River Basin, Upper Paraná River Basin. The samples were taken every two months in seven streams, from October 2006 to August 2007. To examine these data, we used analysis such as cluster, similarity, variance, canonical correspondence and regression tree. We collected 64 species and the spatial variations of the assemblages were more evident than the temporal ones. The most important variables in determining the occurrence of the species were altitude of the region, stream width and depth and water velocity. This result indicates there is an interaction of regional factors (altitude) with local ones (depth, velocity and width) to define the species composition of each stream. The turnover in species composition was significantly influenced by stream depth and altitude. The differentiation on richness and species composition between upper and lower sites should allow richness increment at regional level (hydrographic basin), decreasing the niches overlap and maintenance of sub-populations (for wide-distributed species) which should to resist more to the antropic action over the habitat structure.

O presente trabalho procura caracterizar as comunidades de peixes relacionando a variação espacial e temporal com a organização das comunidades de peixes em riachos da bacia do rio Guiraí, Alto Rio Paraná. As amostragens foram realizadas bimestralmente em sete riachos, entre outubro/2006 e agosto/2007 e, para a análise destes dados, utilizamos análises de agrupamento, de similaridade, de variância, de correspondência canônica e árvore de regressão. Foram coletadas 64 espécies de peixes e a variação espacial das comunidades estudadas se mostrou mais evidente que a variação temporal. As variáveis mais importantes na determinação da ocorrência das espécies foram a altitude do trecho amostrado, largura e profundidade do riacho e velocidade da água, o que indica que há interação de fatores em escala regional (altitude) com fatores locais (profundidade, velocidade e largura) na definição da composição de espécies em cada um dos riachos amostrados. O turnover na composição de espécies foi significativamente influenciado pela profundidade e altitude dos riachos. A diferenciação na riqueza e composição de espécies entre os trechos superiores e inferiores da bacia pode permitir o incremento da riqueza em nível regional (bacia hidrográfica) através da diminuição da sobreposição de nichos, permitindo a manutenção de subconjuntos populacionais (para as espécies de distribuição ampla) que podem resistir melhor às alterações antrópicas na estrutura dos habitats.

Spatial and temporal variation of fish assemblages in a coastal lagoon of the Biosphere Reserve La Encrucijada, Chiapas, Mexico

Composition and abundance of the ichthyofauna in estuarine and coastal lagoon systems of the South Pacific in Mexico have been scarcely studied. In particular, there is a lack of information on how environmental variables determine the spatio-temporal structure of fish assemblages in those habitats. In this study, fishes were sampled by drop net during twelve months (May 2004 -April 2005) in 22 sites distributed along the Carretas-Pereyra lagoon, located in the Biosphere Reserve La Encrucijada, Chiapas, Mexico. We recorded 11 797 individuals (40 species, in 30 genera and 21 families). Dormitator latifrons was the most dominant species in terms of the Importance Value index, IV (23.05 %), followed by Lile gracilis (10.31 %), Poecilia sphenops (8.60 %) and Poecilia butleri (7.30 %). D. latifrons also accounted for more than one half of the total biomass (50.14 %). Species richness and Shannon-Wiener’s diversity indexes showed similar temporal fluctuations, reaching their highest values during the dry season. The system evidenced temporal variations in salinity, having observed four different regimes: freshwater, oligohaline, mesohaline and polyhaline. Mean richness and diversity indexes achieved their highest values during the mesohaline period. On the other hand, mean abundances (CPUE) were highest during the freshwater period. Canonical correspondence analysis (CCA) indicated that salinity and temperature were the most important environmental parameters affecting associations of fishes in terms of their abundances. Correlation analyses revealed that among the environmental variables measured in this study, transparency showed the most significant negative correlation with fish richness and Shannon-Wiener’s diversity index. At a local scale, results suggest that spatial and temporal distribution of fish assemblages are determined by differences in the regimes of salinity and transparency, primarily driven by freshwater input from rivers. Rev. Biol. Trop. 56 (2): 557-574. Epub 2008 June 30.

Se evaluó la influencia de los factores ambientales sobre la variación espacio-temporal de los ensamblajes de peces, en el sistema lagunar Carretas-Pereyra, Chiapas, México. Entre mayo de 2004 y abril de 2005, se realizaron 12 muestreos mensuales en 22 sitios. Se recolectaron 11 797 organismos, pertenecientes a 40 especies, representando a 30 géneros y 21 familias. Dormitator latifrons fue la especie dominante en Índice de Valor de importancia, IV (23.05 %), seguida por Lile gracilis (10.31 %), Poecilia sphenops (8.60 %) y Poecilia butleri (7.30 %). D. latifrons, contribuyó con 50.14 % de la biomasa total. Los valores de riqueza y diversidad de especies (H’) mostraron variaciones temporales similares, siendo más altos en la época de secas que de lluvias. El sistema lagunar presentó variaciones importantes en los valores de salinidad con los siguientes regimenes: agua dulce, oligohalino, mesohalino y polihalino. La riqueza media de especies y la diversidad alcanzaron sus valores más altos durante el periodo mesohalino. Contrario a los valores de riqueza y diversidad, la abundancia promedio (CPUE) presentó los valores más altos durante el régimen de agua dulce.