Papers by Fernando Becker
The Patos Lagoon basin is a large (201 626 km 2 ) and complex drainage system in southern Brazil.... more The Patos Lagoon basin is a large (201 626 km 2 ) and complex drainage system in southern Brazil. The lagoon is 250 km long and 60 km wide, covering an area of 10 360 km 2 . The exchange of water with the Atlantic Ocean occurs through a 0·8 km wide and 15 m deep inlet, fixed by 4 km long jetties, at the southernmost part of the Patos Lagoon. The estuarine area is restricted to its southern portion (10%), although the upper limit of saline waters migrates seasonally and year to year, influenced by the wind regime and river discharge. The known number of recorded limnetic fish species is 200, but this number is expected to increase. A higher endemism is observed in fish species occurring in upper tributaries. The basin suffers from the direct impact of almost 7 million inhabitants, concentrated in small to large cities, most with untreated domestic effluents. There are at least 16 non-native species recorded in natural habitats of the Patos Lagoon basin, about half of these being from other South American river basins. Concerning the fishery, although sport and commercial fisheries are widespread throughout the Patos Lagoon basin, the lagoon itself and the estuarine area are the main fishing areas. Landing statistics are not available on a regular basis or for the whole basin. The fishery in the northern Patos Lagoon captures 31 different species, nine of which are responsible for most of the commercial catches, but only three species are actually sustaining the artisanal fishery: the viola Loricariichthys anus: 455 kg per 10 000 m 2 gillnet per day, the mullet Mugil liza: 123 kg per 10 000 m 2 gillnet per day and the marine catfish Genidens barbus: 50 kg per 10 000 m 2 gillnet per day. A decline of the fish stocks can be attributed to inadequate fishery surveillance, which leads to overfishing and mortality of juveniles, or to decreasing water quality because of urban and industrial activities and power production. Global climatic changes also represent a major threat to the Patos system by changing the frequency of El Niño-La Niña-Southern Oscillation (ENSO).
The relationships between sh composition, connectivity and morphometry of 103 lagoons in nine fre... more The relationships between sh 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 sh species accounted for a signi cant 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 †Author to whom correspondence should be addressed. 281 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 shes.
Spatial position within a dendritic network may determine environmental filters and connectivity ... more Spatial position within a dendritic network may determine environmental filters and connectivity with source of immigrants, influencing species composition and variation in metacommunities. We investigated how long-term turnover of riffle-dwelling fish assemblages is affected by niche-and dispersal-related processes. Multiple linear model selection resulted in four variables important to explain assemblage turnover: (i) habitat change, (ii) channel slope, (iii) dlink (a proxy for connectivity), and (iv) catchment area. These four variables were related to turnover in species abundance, while turnover in species occurrence was only related to habitat change. Models generated for each species indicated they were differently affected by niche-and dispersal-related processes. Our findings provide support for the hypothesis that metacommunity processes affecting temporal turnover of stream fish communities are dependent on the spatial position within a dendritic network, but also vary among species. Our study has implications for sampling design in monitoring programs, as the degree of dissimilarities in fish communities depends not only on local habitat change, but on spatial position within the drainage network and on species particularities.
Connectivity is a key factor in metacommunity ecology, because it influences dispersal and coloni... more 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 (C P ) and estuarine connectivity (C E ), 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 C E , which was distinctively related to each functional fish community richness (directly related to ES and EFS, and inversely related to FS; C P 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.
In forest-grassland mosaics, patches can result from two processes: forest expansion over grassy ... more In forest-grassland mosaics, patches can result from two processes: forest expansion over grassy ecosystems and forest fragmentation.We tested the hypothesis that patches produced by these processes differed in structure and spatial context in a forest-grassland mosaic in the southern Brazilian highlands. We compared a present-day land cover map with a past vegetation map to identify natural forest patches and forest fragments. Patches were described according to structure (size, core area and shape metrics) and spatial context (distance from roads and urban areas, edge contrast). Principal component analyses were used to examine gradients of patch types, and differences were tested by analysis of variance with randomization test. We found 878 natural patches and 214 fragments. Natural forest patches, riparian forest patches and forest fragments differed in structure and spatial context. In comparison to natural forest patches, fragments tend to be larger, with larger core areas, and more irregular and complex in shape. Fragments are situated in a different spatial context, tending to be closer to roads and urban areas and to present higher edge contrast. Riparian natural forest patches are similar to natural forest patches, except for shape. The smaller area and regular shape of natural patches probably result from the mechanisms involved in nucleus formation in the grassland matrix and from current grassland management. Natural patches are less exposed to some anthropogenic stresses, since most of them remain in a native grassland matrix context. Our results show that inferring process from pattern is not trivial, because different processesforest expansion and forest fragmentation -may lead to either distinct or similar patterns of patch shape and spatial context. Studying patch structure and spatial context may then provide further insight into understanding changes in vegetation pattern at landscape scale, and in disentangling the effects of concurrent processes.
Channel slope is an important variable in lotic systems because it mediates flow. However, stream... more 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.
Human activities in the riparian zone can affect the feeding of stream fish because they alter au... more Human activities in the riparian zone can affect the feeding of stream fish because they alter autochthonous production (periphyton, macrophytes and aquatic insects) and allochthonous inputs (terrestrial insects, leaves, seeds and fruits). In the present study we investigated how the diet and intestinal length of a persistent and generalist fish species (Bryconamericus iheringii, Characidae) responds to riparian modifications in 31 subtropical streams in southern Brazil. We hypothesised that intestinal length would be longer in populations inhabiting streams with converted riparian vegetation as a consequence of greater consumption of an indigestible and low-protein diet. Populations of B. iheringii from streams with a degraded riparian zone and reduced canopy cover had longer intestinal length (after accounting for body size), which was associated with decreased consumption of terrestrial plants and invertebrates and increased ingestion of filamentous algae, macrophytes and detritus. These results indicate that anthropic alteration of riparian zones and increased canopy openness trigger shifts in the diet and intestinal length of B. iheringii. The findings suggest that plasticity in intestinal length is an important characteristic to determine whether fish populations can persist in a variety of habitat conditions and cope with the digestion of a greater proportion of low-quality and low-protein food items in humanaltered environments.
Figure 1. (A) Map showing the sample unit where the three specimens of Pseudobunocephalus ihering... more Figure 1. (A) Map showing the sample unit where the three specimens of Pseudobunocephalus iheringii were collected; (B) The dorsal and ventral views of one individual of P. iheringii (UFRGS 20672, SL =30.94 mm).
Figure 1. (A) Map showing the sample unit where the three specimens of Pseudobunocephalus ihering... more Figure 1. (A) Map showing the sample unit where the three specimens of Pseudobunocephalus iheringii were collected; (B) The dorsal and ventral views of one individual of P. iheringii (UFRGS 20672, SL =30.94 mm).
The relationships between fish composition, connectivity and morphometry of 103 lagoons in nine f... more 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
Brazilian journal of biology = Revista brasleira de biologia, 2003
The age and growth of three silverside species are described, and a discussion on possible phylog... more 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 tha...
PLoS ONE, 2014
We used species distribution modeling to investigate the potential effects of climate change on 2... more 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.
Neotropical Ichthyology, 2008
The present study compares the reproduction, condition and size of the small characiform fish, Ch... more 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.
Brazilian Archives of Biology and …, Jan 1, 2002
Feeding habits of six species of Astyanax from river Maquiné are described. Fishes were sampled b... more Feeding habits of six species of Astyanax from river Maquiné 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.
Land cover and conservation state of a region in the Southern limit of the Atlantic Forest (river Maquiné basin, Rio Grande do Sul, Brazil)
Brazilian Journal of …, Jan 1, 2004
The state of conservation of Atlantic Forest in the Maquiné river basin was assessed using land c... more The state of conservation of Atlantic Forest in the Maquiné river basin was assessed using land cover data obtained from Landsat TM 5 satellite imagery (October 1995). The initial analysis examined the distribution of the relative areas of each land-cover type according to landscape slope classes, potential vegetation zones, and a 90 m riparian buffer. Land-cover classes were then regrouped into categories representing "low", "intermediate", and "high" degree of anthropogenic alteration. Results indicate that about 70% of the land cover of the Maquiné river basin has been highly altered as a consequence of replacement of natural forests by agriculture. Presently, a recovery process seems to be underway, contrasting with the historical trend towards deforestation. There are large areas of secondary vegetation in intermediate (34.8%) and advanced successional stages (20.2%), particularly across the range of the montane forest and of forest formations that occur at elevations higher than 800 m (high-montane dense ombrophilous forest and mixed ombrophilous forest). The geographical location at the southern limit of the Atlantic Forest stricto sensu and comparison of the results with data on the state of conservation of the Atlantic Forest in Rio Grande do Sul indicate that the Maquiné river basin is an important area for conservation. Some points regarding future research and conservation management are also discussed.
Hydrobiologia, Jan 1, 2004
The study was done in a first order stream in the southern portion of the Brazilian Atlantic Rain... more 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 Carva˜o 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.
Variação espacial e temporal na abundância de Astyanax bimaculatus e Astyanax fasciatus (Characidae) no lago Guaíba, Rio Grande do Sul, Brasil
Comunicações do Museu de Ciências e …, Jan 1, 1998
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Papers by Fernando Becker