Effects of physical habitat degradation on the stream fish assemblage structure in a pasture region

We compared the fish assemblage structure from streams with different intensities of physical habitat degradation and chemical water pollution by domestic sewage in southeastern Brazil. Eight streams (R1-R8) showing less disturbed or more disturbed conditions of chemical water quality and of physical habitat quality were selected. Cumulative abundance and biomass, combined in ABC plots, revealed (i) biomass curves above the abundance curves, represented by the streams R1-R2 (water and habitat less disturbed) and R5-R6 (water more disturbed and habitat less disturbed), and (ii) biomass curves below the abundance curves, represented by the streams R3-R4 (water less disturbed and habitat more disturbed) and R7-R8 (water and habitat more disturbed). The quantitative structure of the ichthyofauna showed significant correspondence with physical habitat condition but not with chemical water quality. The most significant species to cause the dissimilarity between less disturbed and more disturbed physical habitats was the exotic Poecilia reticulata. Such results indicate that in the focused region-with little influence of industrial pollution, noncritical domestic sewage discharge, and soil predominantly used for pasture-streams with high physical habitat integrity possess a differently structured ichthyofauna than streams with relatively low physical habitat integrity, reinforcing the importance of the physical habitat quality and riparian conservation along these water courses, warranting the conservation of these systems. Indeed, our results also reinforce the importance of including biotic descriptors, particularly of the ichthyo-fauna, in water-monitoring programs designed to reveal signs of human interference.

Biology of a catfish, Trichomycterus sp (Pisces, Siluriformes), in a pristine stream in the Morro do Diabo State Park, southeastern Brazil

The distribution, activity, diet, and reproduction of an undescribed catfish species of the genus Trichomycterus (Trichomycteridae) were studied in the Morro do Diabo State Park, an important conservation area in the Rio Paranapanema basin, State of São Paulo, southeastern Brazil. Trichomycterus sp. is a rheophilic species occurring solely in the riffle areas of the streams and hunts mostly immature aquatic insects during the day by picking them from the substrate. The population has a balanced sex ratio, but females were uncommon in the smallest and largest size classes suggesting that females demonstrate a more accelerated growth pattern. Presence of mature individuals throughout the year represents an opportunistic reproductive tactic for fishes living in fast flowing waters, where the clutches could be shifted by the current, but the high incidence of mature individuals in the wet season may be related to optimal environmental conditions for juveniles during that period. Because of the restriction of Trichomycterus sp. to riffle environments, the conservation of this species depends on the maintenance of the original characteristics of these headwaters. That demands protecting the riparian vegetation and consequently the stream from excessive siltation resulting from runoff and erosion.

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)

From forests to cattail: how does the riparian zone influence stream fish?

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

Riffle and pool fish communities in a large stream of southeastern Brazil

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

Habitat simplification affects nuclear-follower foraging association among stream fishes

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

Feeding association between benthic and nektonic Neotropical stream fishes

A interação nuclear-seguidor tem sido raramente registrada entre peixes de riachos Neotropicais. Este tipo de associação foi observada em um riacho de cabeceira, no sistema do Alto rio Paraná envolvendo o cascudinho, Aspidoras fuscoguttatus, como espécie nuclear, e Knodus moenkhausii, Poecilia reticulata e Astyanax altiparanae como seus seguidores. Indivíduos de Aspidoras fuscoguttatus revolveram o substrato durante alimentação, promovendo a suspensão de sedimento. Os seguidores, por sua vez, movimentaram-se pela nuvem de partículas em suspensão, capturando itens alimentares. As particulas alimentares em suspensão parecem não ser utilizadas pelo cascudinho, mas tornam-se disponíveis para K. moenkhausii, P. reticulata e A. altiparanae. O comportamento de seguidor representa uma tática alimentar alternativa para estas espécies, reforçando a idéia geral de plasticidade comportamental entre as espécies seguidoras.

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)

Effects of artificial substratum types and exposure time on macroalgal colonization in a tropical stream

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

Structure and feeding of a stream fish assemblage in southeastern Brazil: evidence of low seasonal influences

Aim: The present study was developed in a deforested stream located in a region that exhibits marked seasonality with the purpose to investigate whether ecological descriptors of the quantitative structure (i.e., composition, abundance, biomass, species richness, diversity) and feeding of fishes do change between the dry and wet periods. Methods: Sampling was conducted bimonthly from April 2004 to February 2005 by using a standardized effort with electrofishing equipment and environmental variables measurements. Results: We collected 713 fishes belonging to 23 species. The most abundant species were Gymnotus carapo (24.0%) and Poecilia reticulata (23.8%). Species richness, abundance, and biomass showed to be higher in the wet period, but these differences were not significant and did not influence the multivariate pattern of the assemblage (ANOSIM, R = 0.148). Nevertheless, average dissimilarity between community structure in the dry and wet periods was 52.7%, mainly due to the differential contribution of P. reticulata, notably more abundant in the wet season, under quasi-hypoxic water conditions. Examination of 333 gastric contents of 12 species evidenced that food variety was higher in the dry period. of these species, 67% (Astyanax altiparanae, Astyanax fasciatus, Geophagus brasiliensis, Gymnotus carapo, Hypostomus ancistroides, Phalloceros harpagos, Poecilia reticulata, and Rhamdia quelen) kept the diet throughout the year, being classified in the same trophic groups in both periods, and detritus was the most important item for half of them, followed by aquatic insects. Overall, no significant differences in the community's diet between periods were registered (ANOSIM, R = [long dash]0.04). Conclusions: This relative constancy suggests a quite regular availability of resources (mainly shelters in submerged marginal grasses and detritus) along the year.

Fish assemblages in stream stretches occupied by cattail (Typhaceae, Angiospermae) stands in Southeast 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)

Seasonal diet shifts of seven fish species in an Atlantic rainforest stream in Southeastern Brazil

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

Stream fish, water and habitat quality in a pasture dominated basin, southeastern Brazil

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