Disentangling the influences of habitat structure and limnological predictors on stream fish communities of a coastal basin, southeastern Brazil

Em ambientes de riacho, fatores relacionados à estrutura dos habitats e limnologia interagem regulando os padrões de transferência de energia e matéria, afetando a composição da comunidade de peixes. Em bacias costeiras do sudeste do Brasil as características limnológicas e estrutura dos habitats diferem entre riachos de águas claras e pretas. Os primeiros são compostos por uma variedade de tipos de substrato, possuem velocidades de corrente mais elevadas e baixa condutividade, enquanto os últimos apresentam substrato arenoso, baixas velocidades de corrente e águas escuras e ácidas. Neste trabalho analisamos a importância relativa da estrutura dos habitats e das variáveis limnológicas como preditores dos padrões de composição em comunidades de peixes de riachos. Oito riachos de primeira a terceira ordem foram amostrados na planície costeira da bacia do rio Itanhaém. Capturamos 34 espécies e verificamos que a composição das comunidades foi influenciada por fatores estruturais e limnológicos, sendo os primeiros mais importantes. Uma fração de variação que não pode ser totalmente decomposta, deve-se à influência conjunta da limnologia e estrutura dos habitats. Algumas das espécies restritas aos riachos de águas pretas provavelmente apresentam adaptações fisiológicas e comportamentais para lidar com os baixos níveis de pH. Quando foram examinados somente os riachos de águas claras, toda a variação explicada na composição da comunidade de peixes foi atribuída aos fatores estruturais, devido a preferências específicas por diferentes características de hábitats.

Aquatic insects as the main food resource of fish the community in a Neotropical reservoir

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Local and regional ecological drivers of fish assemblages in Brazilian estuaries

Spatial patterns in assemblage structures are generated by ecological processes that occur on multiple scales. Identifying these processes is important for the prediction of impact, for restoration and for conservation of biodiversity. This study used a hierarchical sampling design to quantify variations in assemblage structures of Brazilian estuarine fish across 2 spatial scales and to reveal the ecological processes underlying the patterns observed. Eight areas separated by 0.7 to 25 km (local scale) were sampled in 5 estuaries separated by 970 to 6000 km (regional scale) along the coast, encompassing both tropical and subtropical regions. The assemblage structure varied significantly in terms of relative biomass and presence/absence of species on both scales, but the regional variation was greater than the local variation for either dataset. However, the 5 estuaries sampled segregated into 2 major groups largely congruent with the Brazilian and Argentinian biogeographic provinces. Three environmental variables (mean temperature of the coldest month, mangrove area and mean annual precipitation) and distance between estuaries explained 44.8 and 16.3%, respectively, of the regional-scale variability in the species relative biomass. At the local scale, the importance of environmental predictors for the spatial structure of the assemblages differed between estuarine systems. Overall, these results support the idea that on a regional scale, the composition of fish assemblages is simultaneously determined by environmental filters and species dispersal capacity, while on a local scale, the effect of environmental factors should vary depending on estuary-specific physical and hydrological characteristics © 2013 Inter-Research.

Progressive recovery of a tropical deforested stream community after a flash flood

AIM: In this study, we evaluated and compared community attributes from a tropical deforested stream, located in a pasture area, in a period before (PRED I) and three times after (POSD I, II, and III) a flash flood, in order to investigate the existence of temporal modifications in community structure that suggests return to conditions previous to the flash flood. METHODS: Biota samples included algae, macrophytes, macroinvertebrates, and fish assemblages. Changes in stream physical structure we also evaluated. Similarity of the aquatic biota between pre and post-disturbance periods was examined by exploratory ordination, known as Non-Metric Multidimensional Scaling associated with Cluster Analysis, using quantitative and presence/absence Bray-Curtis similarity coefficients. Presence and absence data were used for multivariate correlation analysis (Relate Analysis) in order to investigate taxonomic composition similarity of biota between pre and post-disturbance periods. RESULTS: Our results evidenced channel simplification and an expressive decrease in richness and abundance of all taxa right after the flood, followed by subsequent increases of these parameters in the next three samples, indicating trends towards stream community recovery. Bray-Curtis similarity coefficients evidenced a greater community structure disparity among the period right after the flood and the subsequent ones. Multivariate correlation analysis evidenced a greater correlation between macroinvertebrates and algae/macrophytes, demonstrating the narrow relation between their recolonization dynamics. CONCLUSIONS: Despite overall community structure tended to return to previous conditions, recolonization after the flood was much slower than that reported in literature. Finally, the remarkably high flood impact along with the slow recolonization could be a result of the historical presence of anthropic impacts in the region, such as siltation, riparian forest complete depletion, and habitat simplification, which magnified the effects of a natural disturbance.

Spatial heterogeneity affecting fish fauna in cascade reservoirs of the Upper Parana Basin, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Testicular structure and description of the seminal pathway in Leporinus macrocephalus (Anostomidae, Teleostei)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Using Amino Acid Correlation and Community Detection Algorithms to Identify Functional Determinants in Protein Families

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Temporal and spatial variability in the macrozoobenthic community along a salinity gradient in the Castillos Lagoon (Uruguay)

The macrozoobenthic community of the Castillos Lagoon system (East Coast of Uruguay) was sampled during autumn, winter, spring and summer of 1991, in order to describe the community structure and the spatial and temporal patterns of distribution. Eleven sampling stations were distributed along a salinity gradient in a north-south direction (8 replicates were collected at each station). The maximum density of organisms was found at the central part of the lagoon (stations 6 and 7) where the bivalve Erodona mactroides and gastropod Heleobia australis were dominants. No significant correlation between the overall abundance of organisms and salinity could be demonstrated (r = 0.43, p > 0.1). However, a reduction in organism abundance between the autumn and the summer coincided with a marked drop in salinity. Falling levels of dissolved oxygen could have influenced the decreasing density of organisms (r = 0.75, p < 0.05). Species richness and diversity were correlated (p < 0.1) with salinity but the degree of correlation was not uniformly significant between sampling periods.

Reduction of a native fish fauna by alien species: an example from Brazilian freshwater tropical lakes

The consequences of introducing Cichla cf. monoculus Spix & Agassiz, Astronotus ocellatus (Agassiz) and Pygocentrus nattereri Kner into lakes in the River Doce basin, Brazil, on richness, diversity and efficiency of aquatic macrophytes as natural refugia to native fishes was investigated. Samples were taken from lakes with and without alien fishes in areas with and without aquatic macrophytes. The presence of alien fishes reduced richness and diversity of the native fish community. The refugia function, which could be attributed to the clustering of aquatic macrophytes, does not exist in these lakes probably because the alien fishes exploit such habitats for reproduction. Since introductions threaten the native fish diversity of the region, studies on regional dispersion and factors that minimise the spread of alien fishes are needed.

Short-term successional dynamics of a macroalgal community in a stream from northwestern São Paulo State, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Grass-dominated stream sites exhibit low fish species diversity and dominance by guppies: an assessment of two tropical pasture river basins

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Testing the ecomorphological hypothesis in a headwater riffles fish assemblage of the rio São Francisco, southeastern Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of the riparian zone phytophysiognomies on the longitudinal distribution of fishes: evidence from a Brazilian savanna stream

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Changes in coral reef communities and an associated reef fish species, Cephalopholis cruentata (Lacepede), after 30 years on Curacao (Netherlands Antilles)

Using the same methodology and identical sites, we repeat a study dating from 1973 and quantify cover of hard coral species, soft corals, sponges, hard substratum and soft substratum, and density of a commercially important reef fish species, the graysby Cephalopholis cruentata, along a depth-gradient of 3-36 m oil the coral reefs of Curacao. The objective was to determine the multi-decade change in benthic coral reef cover and structural complexity, and their effect oil densities of an associated reef fish species. Total hard coral cover decreased on average from 52% in 1973 to 22% in 2003, representing a relative decline of 58%. During this time span, the cover of hard substratum increased considerably (from 11 to 58%), as did that of soft corals (from 0.1 to 2.2%), whereas the cover of sponges showed no significant change. Relative decline of hard coral cover and of reef complexity was greatest in shallow waters (near the coast), which is indicative of a combination of anthropogenic influences from shore and recent storm damage. Cover of main reef builder coral species (Agaricia spp., Siderastrea siderea, Montastrea annularis) decreased more than that of other species, and resulted in a significant decrease in reef complexity. Although density of C. cruentata was highly correlated to cover of Montastrea and Agaricia in 1973, the loss of coral cover did not show any effect on the total density of C. cruentata in 2003. However, C. cruentata showed a clear shift in density distribution from shallow water in 1973 to deep water in 2003. It call be concluded that the reefs of Curacao have degraded considerably in the last three decades, but that this has had no major effect on the population size of one commercially important coral-associated fish species.

Spatial and seasonal patterns in fish assemblage in Córrego Rico, upper Paraná river Basin

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)