Fernando Becker

Diet of Astyanax species (Teleostei, Characidae) in an Atlantic Forest River in Southern Brazil

Feeding habits of six species of Astyanax from river Maquine are described. Fishes were sampled bi-monthly from November/95 to September/96 in two zones of the river. Items were identified, counted and had their abundance estimated according to a semi-quantitative scale. Frequency of occurrence, alimentary importance index (IFI) values and a similarity analysis of diets for each species-river zone sample were examined. All the species were considered typically omnivorous, with insects and vegetal matter being the most important items in their diet. These species could act as seed dispersers, particularly for macrophytes. Intra-specific spatial differences were not observed in comparisons of samples from two diferent regions of the river, except for A. fasciatus. The presence of Podostemaceae macrophytes in the mid-course of the river seemed to be important both as an autochthonous food resource and as habitat for several organisms preyed by the Astyanax species.

Relation between environmental variables and aquatic megafauna in a first order stream of the Atlantic Forest, southern Brazil

The study was done in a first order stream in the southern portion of the Brazilian Atlantic Rain Forest. Samples of the aquatic megafauna (amphibians, crustaceans and fishes) were taken with the aim of describing spatial (longitudinal) and temporal (seasonal) patterns in species composition and abundance. Thirty four structural and limnological variables at macro and mesoscales from three sampling reaches were analysed. The spatio-temporal analysis of species richness and diversity indicated a gradient in which values increased in an upstream–downstream direction, independently of the season of the year. The results showed a strong influence of structural environmental variables on community structure. Furthermore, they revealed a hierarchical relation between macroscale and mesoscale variables and their influence on community abundance and composition in the various spatio-temporal sampling units analysed. The spatial distribution of species richness and diversity in the Carvão creek was strongly influenced by the presence of waterfalls, being progressively richer and more diverse downstream. Waterfalls seem to function as selective filters more than as absolute barriers, presenting different efficiencies for different species.

Novas possibilidades da pesquisa qualitativa via sistemas CAQDAS

Os manuais de metodologia qualitativa, nao trazem nenhuma informacao direta sobre o uso de pacotes para a analise de dados qualitativos, que, alem disto sao relativamente desconhecidos no Brasil. De outro lado, o uso destes programas torna-se imprescindivel para a pesquisa sociologica devido a grande economia de recursos e tempo, mas tambem pela possibilidade de gerar analises mais ricas e aprofundadas. Este texto visa apontar os recursos oferecidos por estes programas de analise de dados qualitativos, especialmente o QSR NUD*IST, e como funcionam. Importa contribuir para a discussao sobre como operacionalizar a pesquisa sociologica utilizando estes pacotes, que servem como uma poderosa ferramenta para as diferentes tecnicas de pesquisa qualitativa.

Climate Change and the Distribution of Neotropical Red-Bellied Toads (Melanophryniscus, Anura, Amphibia): How to Prioritize Species and Populations?

We used species distribution modeling to investigate the potential effects of climate change on 24 species of Neotropical anurans of the genus Melanophryniscus. These toads are small, have limited mobility, and a high percentage are endangered or present restricted geographical distributions. We looked at the changes in the size of suitable climatic regions and in the numbers of known occurrence sites within the distribution limits of all species. We used the MaxEnt algorithm to project current and future suitable climatic areas (a consensus of IPCC scenarios A2a and B2a for 2020 and 2080) for each species. 40% of the species may lose over 50% of their potential distribution area by 2080, whereas 28% of species may lose less than 10%. Four species had over 40% of the currently known occurrence sites outside the predicted 2080 areas. The effect of climate change (decrease in climatic suitable areas) did not differ according to the present distribution area, major habitat type or phylogenetic group of the studied species. We used the estimated decrease in specific suitable climatic range to set a conservation priority rank for Melanophryniscus species. Four species were set to high conservation priority: M. montevidensis, (100% of its original suitable range and all known occurrence points potentially lost by 2080), M. sp.2, M. cambaraensis, and M. tumifrons. Three species (M. spectabilis, M. stelzneri, and M. sp.3) were set between high to intermediate priority (more than 60% decrease in area predicted by 2080); nine species were ranked as intermediate priority, while eight species were ranked as low conservation priority. We suggest that monitoring and conservation actions should be focused primarily on those species and populations that are likely to lose the largest area of suitable climate and the largest number of known populations in the short-term.

Life-history of the South American darter, Characidium pterostictum (Crenuchidae): evidence for small scale spatial variation in a piedmont stream

The present study compares the reproduction, condition and size of the small characiform fish, Characidium pterostictum, sampled at close sites differing in severity of flash flood effects. Data were obtained from seasonal samples in two sites situated 8 km apart in the same stream. In the upstream site, habitat is more severely affected by flash floods than in the downstream site, and this difference was hypothesized to produce differences in life history and individual reproduction trade-off patterns, as predicted by life-history theory. The results provided evidence for small-scale spatial variation in life-history and trade-off patterns within the studied population. At the most severely disturbed site, C. pterostictum displayed a trade-off pattern that favored reproductive life-span (e.g., larger size, higher and seasonally stable condition, larger mean size of mature females) over instantaneous reproductive output (lower gonadosomatic index), while the opposite pattern was observed in the less disturbed site. Because of the differences in disturbance effects between each sampling site, these results suggest that withinstream variability in the severity of hydrological disturbance can influence life-history patterns at small spatial scales. An implication of the results is that fish occupying areas that are hydrologically more variable within a stream are not necessarily at an energetic or reproductive disadvantage, but may be simply under environmental conditions that favor distinct patterns of energy allocation (or trade-offs) and population persistence, as predicted by life-history theory. Therefore, plasticity in lifehistory is expected to be common in stream fish populations that are widespread in a stream system with spatially variable or patchy habitat characteristics. Este estudo compara a estrutura populacional e a reproducao do pequeno caraciforme, Characidium pterostictum, amostrado em locais sujeitos a diferentes efeitos de perturbacoes hidrologicas naturais (enxurradas). Os dados foram obtidos a partir de amostragens sazonais em dois trechos distando 8 km entre si, no mesmo riacho. No trecho a montante, o habitat e mais severamente afetado pelas enxurradas do que no trecho a jusante e, devido a esta diferenca, testou-se a hipotese de que haveria contrastes em padroes de alocacao de energia entre reproducao e sobrevivencia individual, como previsto pela teoria de historia de vida. No trecho a montante, C. pterostictum apresentou caracteristicas que favorecem a longevidade reprodutiva (como maior tamanho, condicao mais elevada e sazonalmente pouco variavel, maior tamanho de femeas maduras) em relacao ao desempenho reprodutivo instantâneo (menor indice gonadossomatico). O padrao oposto foi observado no trecho a jusante. Devido as diferencas em termos de efeito de perturbacao (enxurradas) em cada trecho, esses resultados sugerem que a variabilidade espacial de perturbacoes hidrologicas pode influenciar padroes de historia de vida dentro de uma populacao. Outra implicacao dos resultados, e que os peixes que ocupam locais hidrologicamente mais variaveis em um riacho nao estao necessariamente em desvantagem energetica ou reprodutiva, mas podem estar simplesmente sob condicoes ambientais que favorecem padroes distintos de alocacao de energia e persistencia da populacao. Dessa forma, pode-se esperar que a plasticidade de historia de vida seja comum em populacoes de peixes que sejam amplamente distribuidas em um sistema de riachos com caracteristicas de habitat espacialmente variaveis ou em mosaico.

Lake connectivity and fish species richness in southern Brazilian coastal lakes

Connectivity is a key factor in metacommunity ecology, because it influences dispersal and colonization rates. However, it has received less attention in aquatic than in terrestrial ecology research. We investigated whether connectivity is a good predictor of species richness in functional fish communities (freshwater, FS; estuarine, ES and estuarine-freshwater, EFS) from 31 coastal lakes in southern Brazil. We used a model selection approach, including lake area and distance from the ocean as additional predictors of species richness and two connectivity metrics: primary connectivity (CP) and estuarine connectivity (CE), which measure connectivity to neighboring lakes and system-wide connectivity, respectively. Both metrics estimate functional connectivity and were calculated on habitat-based cost distances. Connectivity was more important for predicting richness of functional communities than for total richness, particularly CE, which was distinctively related to each functional fish community richness (directly related to ES and EFS, and inversely related to FS; CP was related only to ES). Remarkably, connectivity was more important than area for predicting ES and EFS richness. These results add support to dispersal limitation as an important mechanism influencing fish communities. We suggest that incorporating environmental filters (habitat type) to quantify connectivity is useful for accessing the patterns of species richness.

Photo-identification as a technique for recognition of individual fish: a test with the freshwater armored catfish Rineloricaria aequalicuspis Reis & Cardoso, 2001 (Siluriformes: Loricariidae)

Photo-identification allows individual recognition of animal species based on natural marks, being an alternative to other more stressful artificial tagging/marking techniques. An increasing number of studies with different animal groups has shown that photo-identification can successfully be used in several situations, but its feasibility to study freshwater fishes is yet to be explored. We demonstrate the potential use of photo-identification for intraspecific recognition of individuals in the stream-dwelling loricariid Rineloricaria aequalicuspis . We tested photo-identification in laboratory and field conditions based on the interindividual variability in abdominal bony plates. Our test yielded high correct matches in both laboratory (100%) and field conditions (> 97%), comparable to other reliable techniques and to studies that successfully used photo-identification in other animals. In field conditions, the number of correct matches did not differ statistically between computer-assisted and naked-eye identification. However, the average time expended to conclude computer-assisted photo evaluations was about half of the time expended to conclude naked-eye evaluations. This result may be exacerbated when using database with large number of images. Our results indicate that photo-identification can be a feasible alternative technique to study freshwater fish species, allowing for a wider use of mark-recapture in ecological and behavioral studies.

Fish composition and species richness in eastern South American coastal lagoons: additional support for the freshwater ecoregions of the world.

The relationships between fish composition, connectivity and morphometry of 103 lagoons in nine freshwater ecoregions (FEOW) between 2·83° S and 37·64° S were evaluated in order to detect possible congruence between the gradient of species richness and similarities of assemblage composition. Most lagoons included in the study were <2 km(2) , with a maximum of 3975 km(2) in surface area. Combined surface area of all lagoons included in the study was 5411 km(2) . Number of species varied locally from one to 76. A multiple regression revealed that latitude, attributes of morphometry and connectivity, and sampling effort explained a large amount of variability in species richness. Lagoon area was a good predictor of species richness except in low latitude ecoregions, where lagoons are typically small-sized and not affected by marine immigrants, and where non-native fish species accounted for a significant portion of species richness. Relationships between species and area in small-sized lagoons (<2 km(2) ) is highly similar to the expected number in each ecoregion, with systems located between 18·27° S and 30·15° S attaining higher levels of species richness. Similarities in species composition within the primary, secondary and peripheral or marine divisions revealed strong continental biogeographic patterns only for species less tolerant or intolerant to salinity. Further support for the FEOW scheme in the eastern border of South America is therefore provided, and now includes ecotonal systems inhabited simultaneously by freshwater and marine species of fishes.

Age and growth of three Odontesthes species from Southern Brazil (Atherinopsidae), with reference to phylogenetic constraints in their life-history

The age and growth of three silverside species are described, and a discussion on possible phylogenetic constraints on life-history characteristics is presented. Samples were collected monthly between March 1992 and February 1993 in three freshwater coastal lakes. Standard length-total length (Ls-Lt) and weight-length (Wt-Lt) relationships studied showed interspecific differences in comparisons between juveniles and adults, males and females. Age was determined by scales. The three species presented a life-cycle duration of 4 to 5 years, with growth coefficients values (K) between 0.37 and 0.63, and asymptotic lengths between 211 and 257 mm. Some interspecific differences may be useful for distinguishing between species (sexual and life-stage related patterns in Ls-Lt and Wt-Lt). The observed life-cycle ranges and maximum sizes were compared to those of other silversides and revealed a pattern coherent with available phylogenetic hypotheses at the supra-generic level, indicating that some life-history characteristics may be subject to phylogenetic constraints.

Relation between species richness and stream slope in riffle fish assemblages is dependent on spatial scale

Channel slope is an important variable in lotic systems because it mediates flow. However, stream slope can be measured at various spatial scales and the relation with fish assemblage characteristics may be scale dependent. In this study we investigated the influence of stream slope measured at different spatial scales on fish species richness. We tested three hypotheses: 1) the relation between slope and species richness will be dependent on the spatial scale at which slope is measured; 2) species richness will be inversely related to mean stream slope; 3) species richness will be positively related to stream slope variability. We sampled riffle fish assemblages in 21 streams in southern Brazil. For each stream we measured slope at five different scales and calculated mean slope and slope variation. The influence of slope on local species richness was tested by simple regression analysis using rarefied richness as response variable. We found that the relation between slope and species richness was scale-dependent, because only slope at the whole stream channel was significantly related to species richness. We also observed that steeper streams tended to have less slope variability and lower species richness. These results suggest that processes occurring at the whole stream scale are determinant for local fish species richness. More importantly, they reinforce the need to measure slope at different scales when investigating fish-habitat relations in streams, because the influence of slope may not be detected if assessed at only one scale. We suggest that assessing mean slope and slope variability at different scales should be considered in sampling design of research and conservation aimed at stream fishes.