Francisco Leonardo Tejerina-Garro

Changes in the structure of fish assemblages in streams along an undisturbed-impacted gradient, upper Paraná River basin, Central Brazil

The Joao Leite River is located in the upper Parana basin, Central Brazil. It drains areas covered by Cerrado vegetation interspersed with urban and agricultural areas. This study aims to asses changes of the fish assembleges structure along a undisturbed-impacted gradient in ten stream stretches using ecological descriptors, a similarity index and the abundance-biomass relationship (ABC curves). The fish were collected during the dry period using electrofishing gear in stretches of 50 m. Results show that the environmental variation observed along the undisturbed-impacted gradient considered influences on fish assemblage structure. Both richness and diversity differences between fish assemblages are partially influenced by stream stretch orthonian order and anthropogenic impacts. ABC curves classified six stream stretches located in preserved or impacted areas as undisturbed while four stretches were classified as disturbed. This is attributed to the influence of the undisturbed habitat within the conservation unit and the presence of K- or r- strategist species. This type of study contributes to an understanding of the effects of aquatic environment conservation on the Brazilian Cerrado core area, where the choice of conservation areas prioritizes terrestrial over aquatic aspects.

Influence of environmental variables and anthropogenic perturbations on stream fish assemblages, Upper Paraná River, Central Brazil

The Ouvidor River, a tributary of the Upper Parana River, drains areas covered by cerrado vegetation in Central Brazil. We collected data for environmental variables (water temperature, dissolved oxygen, pH, conductivity, turbidity, water velocity, luminosity, channel substrate and width) and anthropogenic perturbations (industry, reservoirs, urban areas) that may structure the fish assemblage in ten stream sites of the Ouvidor River basin. In each stream we delimited one 50 m long site where fish were captured by electrofishing and abiotic data were collected every two month between August 2004 and June 2005. Co-inertia analysis indicated that pH, water velocity, channel width and water temperature most strongly structured the fish assemblages. The interactions of water velocity and channel width with the fish assemblage were not directly affected by wet and dry seasons but the opposite was true for pH and water temperature.

Flow seasonality and fish assemblage in a tropical river, French Guiana, South America

The objective of this study is to verify the existence of a seasonal pattern of variation in the fish assemblages of a tropical river using taxonomic and functional descriptors. Fish were sampled using gillnets at two sites on the Comte River, a large-sized river 254.8 km long, flowing entirely through rainforest areas of French Guiana. Samplings were conducted every other month from August 1998 to July 2000. Four types of fish assemblage descriptors were used: the species descriptor (number of individual fish of each species in the sample); the family descriptor (number of individual fish of each family in the sample); the trophic descriptor (distribution of the fish biomass in each feeding guild) and the specific maximum observed size - MOS (number of individual fish in each of four classes of MOS: 300 mm). Results point out that changes in the fish assemblage are related to water level oscillations. The role of migration seems to be weak and is limited to trophic displacements characteristic of few species. In the low-water season, characterized by weak water level oscillation, fish species and families belonging to piscivorous or aquatic invertivorous guilds were predominant, whereas in the high-water season the environment is submitted to strong variations caused by fast and large water level oscillations, and the fish assemblage was characterized by species or families with an opportunistic omnivorous diet.

Influence of environmental parameters on fish assemblage of a neotropical river with a flood pulse regime, Central Brazil

Este estudo determinou quais entre doze parâmetros ambientais (cinco fisico-quimicos e sete hidromorfologicos) influenciam na estrutura da assembleia de peixes do baixo rio das Mortes localizado na planicie de inundacao do Bananal, bacia do rio Araguaia, Brasil Central. As coletas foram realizadas em seis trechos de 1000 m cada durante os periodos de chuva e estiagem, nos quais 1036 peixes foram coletados utilizando-se redes de malhar e medidos os parâmetros ambientais utilizando equipamentos portateis ou determinados visualmente. A analise de coinercia indicou que dois parâmetros fisicos e quimicos (oxigenio dissolvido e a transparencia da agua) e quatro hidromorfologicos (largura e profundidade da calha principal, cobertura da mata riparia e tipo de substrato da margem) estruturam a assembleia de peixes, ambos influenciados pelo regime hidrologico regional (pulso de inundacao). Estes resultados sao discutidos considerando a interacao entre peixes e os parâmetros ambientais caracteristicos dos sistemas aquaticos Neotropicais.

Assessment of fish assemblages in streams of different orders in the Upper Paraná River basin, Central Brazil

The aim of this study was to test whether the richness observed and the biomass per trophic group of fish assemblages vary depending on the order (1st and 2nd) of the streams located in three different basins of the Upper Parana River Basin, Central Brazil. Samples were collected between April and September, 2009, in 27 streams of the Meia Ponte, Piracanjuba and Santa Maria River basins. A total of 4,879 specimens were collected distributed in 59 species and 19 families. The statistical analyses carried out indicate that the observed richness and biomass of omnivore fish were influenced by the interaction of two factors: stream order and basin. The 2nd order streams located in the Santa Maria basin presented significant differences in the observed richness and omnivore biomass when compared to i) 1st order streams in the same basin (only richness) or in the Piracanjuba and Meia Ponte basin; ii) 2nd order streams in the Piracanjuba (only omnivore biomass) and Meia Ponte Rivers basins. Results are discussed considering the influence of geomorphic processes on fish assemblages and food availability.

Headwater–river gradient: trait-based approaches show functional dissimilarities among tropical fish assemblages

Traditionally, species richness and composition of freshwater communities are expected to change according to the structural variation from headwaters to river mouth. In the present study, we hypothesised that fish functional traits will respond to this gradient, leading to functional dissimilarities between fish assemblages of headwaters and those of rivers. We addressed the following questions: (1) which functional traits are present in fish assemblages of each habitat type; (2) which environmental factors determine the occurrence of fish functional traits; and (3) how functional traits are related to each environmental variable? Our findings showed dissimilarities between fish assemblages of headwaters and those of rivers, mainly driven by channel depth, channel width, water temperature, water turbidity and concentration of dissolved oxygen, whereas altitude, water temperature and pH were mainly correlated with variation within each habitat type. These results suggested that not only do the physical variables proposed in classical theory of the river-continuum concept follow the upstream–downstream gradient in structuring the functional organisation of fish assemblages, but that also physicochemical variables, such as turbidity and concentration of dissolved oxygen, display this trend in tropical river systems. Moreover, our results have given a first perspective on what kind of fish species and fish functional traits to expect in each habitat type and, consequently, along the headwater–river mouth gradient.

O incentivo à pesca comercial de Arapaima gigas (pirarucu) do rio Araguaia (Brasil central) na revista “A Informação Goyana” (1917-1935)

Between 1917 and 1935, the magazine A Informação Goyana sporadically published several photos of specimens of Arapaima gigas (arapaima) captured in the Araguaia River. This present article follows the interconnections formed by the photographic record of this species and its appearance in this magazine, in an attempt to analyze efforts to integrate the state of Goiás into Brazil through developing a fishing industry, which did not yet existent in that state. This effort coincided with the emergence of a national debate on incentives for fishing and the formation of a domestic market arapaima as a way to reduce cod imports. These images emphasized the biodiversity of the aquatic animals inhabiting the rivers in Goiás, the size and weight of arapaima from the Araguaia Basin, and the potential of large-scale fishing of this species for the economic development of the state.

Effects of area and available energy on fish assemblages of tropical streams

A central issue in fish community ecology is to understand how the size of the drainage area and the available energy influence fish species diversity and their spatial distribution. In the present study, we tested whether the species–area relationship (represented by drainage area) and species–energy association (represented by algal biomass and organic matter) drive taxonomic and functional richness in a regional scale. The results indicated that fish assemblages of the two tropical neighbouring basins sampled responded differently to the size of drainage area. Whereas taxonomic richness was influenced by the size of the drainage area in Tocantins River basin streams, it was not affected in Araguaia River basin streams. Both taxonomic richness and functional richness of the fish assemblages were affected by available energy in the system. A possible explanation for these different responses is related to local conditions, such as the percentage of natural vegetation cover encountered in each basin.