Angelo Antonio Agostinho - Academia.edu (original) (raw)

Papers by Angelo Antonio Agostinho

River Research and Applications

Environmental Biology of Fishes

ABSTRACT This study evaluated the relationship between the young of year (YOY) abundance of migra... more ABSTRACT This study evaluated the relationship between the young of year (YOY) abundance of migratory fish species and the interannual variations in the duration and delay of floods in the Upper Paraná River floodplain. YOY of the most abundant migratory species Brycon orbignyanus, Hemisorubim platyrhynchos, Leporinus elongatus, Leporinus macrocephalus, Leporinus obtusidens, Pseudoplatystoma corruscans, Pterodoras granulosus, Prochilodus lineatus, Salminus brasiliensis and Sorubim lima were studied in a stretch of the Paraná river influenced by dams. Multiple regression analyses were performed with flood duration and delay as predictors for YOY abundances. There were differences among the species in the responses to flood duration and delay. The species B. orbignyanus, L. elongatus, L. macrocephalus, L. obtusidens, and P. lineatus exhibited an exponential increase in YOY abundance with flood duration. An exponential decrease in YOY abundance with flood delay was found for most of the studied species. Nevertheless, flood delay and flood duration were significant predictors of YOY abundance for L. elongatus, L. obtusidens, P. corruscans and P. lineatus. For these species, flood delays may result in failure of recruitment because these species migrate early in the season to adjust their energy reserves and their swimming patterns. Therefore, any efforts to preserve migratory fish should consider discharge manipulation from reservoirs upstream of the study areas. It is crucial that reservoirs are operated in such a way that the quantity, duration and timing of water release are compatible with the viability of spawning and the survival of early life stages of migratory fish.

Neotropical Ichthyology

The limiting similarity theory predicts that divergence in the functional traits of native and in... more The limiting similarity theory predicts that divergence in the functional traits of native and introduced species is an essential component in species establishment, as introduced species must occupy a niche that is unoccupied by resident species. On the other hand, the environmental filtering hypothesis predicts convergence between introduced and native species, as both possess traits that make them adapted to the local abiotic environment. Morphology, spatial co-occurrence, diet, feeding selectivity, and niche breadth and overlap of Erythrinidae were evaluated to detect possible mechanisms acting in the coexistence between non-native and native species. Native (Hoplias sp. B and Hoplias cf. malabaricus) and non-native (Hoplerythrinus unitaeniatus and Hoplias mbigua) species presented differences in morphological traits, spatial co-occurrence, diet, selectivity, and niche breadth and overlap. The mechanisms mediating species coexistence seem to vary according to species. The absenc...

Neotropical Ichthyology

Populations show spatial-temporal fluctuations in abundance, partly due to random processes and p... more Populations show spatial-temporal fluctuations in abundance, partly due to random processes and partly due to self-regulatory processes. We evaluated the effects of various external factors on the population numerical abundance of curimba Prochilodus lineatus in the upper Paraná River floodplain, Brazil, over a 19-year period. Panel data analysis was applied to examine the structure of temporal and spatial abundance while controlling auto-regressive processes and spatial non-homogeneity variances that often obscure relationships. As sources of population variation, we considered predation, competition, selected abiotic variables, construction of a dam upstream of the study area, water level and flood intensity during the spawning period. We found that biological interactions (predation and competition) were not significantly related to variations in curimba abundance; specific conductance was a space indicator of abundance, apparently linked to the biology of the species; intensity ...

PloS one, 2017

Climate change and species invasions interact in nature, disrupting biological communities. Based... more Climate change and species invasions interact in nature, disrupting biological communities. Based on this knowledge, we simultaneously assessed the effects of climate change on the native distribution of the Amazonian fish Colossoma macropomum as well as on its invasiveness across river basins of South America, using ecological niche modeling. We used six niche models within the ensemble forecast context to predict the geographical distribution of C. macropomum for the present time, 2050 and 2080. Given that this species has been continuously introduced into non-native South American basins by fish farming activities, we added the locations of C. macropomum farms into the modeling process to obtain a more realistic scenario of its invasive potential. Based on modelling outputs we mapped climate refuge areas at different times. Our results showed that a plenty of climatically suitable areas for the occurrence of C. macropomum occurrence are located outside the original basins at the ...

PloS one, 2017

Cannibalism has been commonly observed in fish from northern and alpine regions and less frequent... more Cannibalism has been commonly observed in fish from northern and alpine regions and less frequently reported for subtropical and tropical fish in more diverse communities. Assuming all else being equal, cannibalism should be more common in communities with lower species richness because the probability of encountering conspecific versus heterospecific prey would be higher. A global dataset was compiled to determine if cannibalism occurrence is associated with species richness and latitude. Cannibalism occurrence, local species richness and latitude were recorded for 4,100 populations of 2,314 teleost fish species. Relationships between cannibalism, species richness and latitude were evaluated using generalized linear mixed models. Species richness was an important predictor of cannibalism, with occurrences more frequently reported for assemblages containing fewer species. Cannibalism was positively related with latitude for both marine and freshwater ecosystems in the Northern Hemis...

Acta Scientiarum Biological Sciences, May 9, 2008

RESUMO. Com o objetivo de avaliar a composição da ictiocenose de lagoas da planície aluvial do al... more RESUMO. Com o objetivo de avaliar a composição da ictiocenose de lagoas da planície aluvial do alto rio Paraná em relação às categorias tróficas, foram realizadas coletas nas lagoas Figueira, Genipapo e Pousada, em março/1999. Após as capturas e obtenção dos dados biométricos, os peixes foram eviscerados e os estômagos fixados em formol 4%. Os conteúdos estomacais foram analisados pelos métodos de freqüência de ocorrência e volumétrico combinados no Índice Alimentar (IAi). Foram amostradas 40 espécies, as quais foram agrupadas em 10 categorias tróficas, ou seja, detritívora, iliófaga, zooplanctófaga, algívora, carcinófaga, piscívora, insetívora, bentófaga, herbívora e onívora. Para a lagoa Pousada, foram importantes, em número, as categorias zooplanctófagas (48,31%), na lagoa Genipapo foram os iliófagos (74,96%), enquanto que para a lagoa Figueira algívoros sobressaíram, com 75,58% da captura, s. Em relação à biomassa, observou-se que detritívoros foram dominantes na lagoa Pousada (45,7%) e lagoa Figueira (27,7%), enquanto que na lagoa Genipapo predominaram os iliófagos (90,0%). Registrou-se alta disponibilidade de camarões nas três lagoas, embora estes tenham sobressaído apenas na dieta dos peixes da lagoa Figueira (20,7%). Embora a maior distância entre as três lagoas seja inferior a 1km, elas são submetidas a diferentes níveis de influência do rio Paraná, e apresentam fisiografias distintas e composições ictiofaunísticas diversas. Além disso, várias espécies icticas apresentam dietas distintas conforme a lagoa considerada, revelando papeis distintos na cadeia trófica desses ambientes. Palavras chave; estrutura trófica, alimentação de peixes, lagoas. ABSTRACT. Trophic characterization of ichthyofauna from three lagoons of the Upper Paraná river floodplain, Brazil. Ichthyofauna from three lagoons of the upper Paraná River floodplain was evaluated according to trophic categories. Samples were obtained in the Figueira, Genipapo, and Pousada lagoons in March 1999. Stomach contents were analyzed according to methods of occurrence and volumetric frequency, combined in an alimentary index (IAi). Forty species were caught and grouped in ten trophic categories (detritivorous, ileophagous, zooplankton-feeder, algivorous, shrimp eater, piscivorous, insectivore, bentophagous, herbivore and omnivore). Zooplankton feeders (48.3%) predominated in the Pousada Lagoon, ileophagous species (74.9%) in the Genipapo Lagoon and algivorous species (75.6%) in the Figueira Lagoon. With regard to biomass, detritivorous predominated in the Pousada (45.7%) and Figueira (27.7%) lagoons, and ileophagous (90.0%) were dominant in the Genipapo Lagoon. Although the distance among lagoons is less than 1 km, the degree of influence from the Paraná river is different, since lagoons have distinct physiography and ichthyofauna composition. Several fish species presented different diets depending on the lagoon and reveal that they play distinct roles in the trophic chain of these environments.

Hydrobiologia, Nov 30, 1998

Base de dados : REPIDISCA. Pesquisa : 48804 [Identificador único]. Referências encontradas : 1 [r... more Base de dados : REPIDISCA. Pesquisa : 48804 [Identificador único]. Referências encontradas : 1 [refinar]. Mostrando: 1 .. 1 no formato [Detalhado]. página 1 de 1, 1 / 1, REPIDISCA, seleciona. para imprimir. Id: 48804. Autor: Agostinho, Angelo A; Gomes, Luiz C. ...

Environ Biol Fish, 1996

Environmental Biology of Fishes 46: 297-307.1996. 0 1996 Kluwer Academic Publishers. Printed in t... more Environmental Biology of Fishes 46: 297-307.1996. 0 1996 Kluwer Academic Publishers. Printed in the Netherlands. ... Feeding styles of five species of bottom-feeding fishes of the high Paran ... Rosemara Fugi, Norma Segatti Hahn & Angelo Antonio Agostinho Nucleo de ...

River Res Appl, 2009

Fish community surveys were conducted in five tributaries of the Corumbá River before and after d... more Fish community surveys were conducted in five tributaries of the Corumbá River before and after damming. Electrofishing samples were collected monthly in the pre-impoundment period (March 1996 to August 1996) and 15 in the post-impoundment period (September 1996 to February 1999). A self-organizing map (SOM, an Artificial Neural Network algorithm) was used to represent the patterns of fish assemblages. Samples collected in both the pre-and post-impoundment periods were randomly dispersed on the SOM, and, therefore, a clear and significant pattern of separation between samples collected during these two time periods was not found. Mean and maximum water depth, which is correlated with ground water level, did not significantly separate the pre-and post-impoundment samples. However, we found significant differences between the two periods for water temperature, pH, conductivity, DO and current velocity, but abundances of fish species (summarized in the clusters identified by the SOM) did not differ significantly. Instead, the validity of the clusters distinguished by the SOM was confirmed by significant differences in some biotic variables: species richness, equitability and log transformed total abundance. Indicator species values identified the most preferred cluster (and respective complex of environmental factors) for a given species. Only one cluster did not contain any significant species indicator values, but it was dominated by samples from the Furnas Stream, which was the only effluent that could be entered by fish from the main river channel after the damming owing to its location below the dam, which has no fish ladder.

Fish Res, 2002

Fishery yields in reservoirs of the Upper Paraná River basin are small when compared to those in ... more Fishery yields in reservoirs of the Upper Paraná River basin are small when compared to those in other parts of the world. Several hypotheses have been formulated to explain the small yields, but low primary production has not been seriously considered as a possibility. In a sample of seven reservoirs, yield was directly related to fishing effort and chlorophyll a concentration; thus, enhancement of these factors may boost yield. However, primary production is difficult to augment in large reservoirs, plus current levels of effort seem to be nearing maximum sustainable yields in some reservoirs, and therefore increased fishing effort is not likely to boost yields to levels recorded in other geographical regions. Low primary production in reservoirs of the Upper Paraná River basin appears to be a result of interactions between physical characteristics of the reservoirs and climatic conditions of the region.

Aquatic Ecosystem Health Management, 2007

River Research and Applications, Apr 30, 2002

The reproductive strategies of potamodromous fish of the Plata basin involve upstream migration a... more The reproductive strategies of potamodromous fish of the Plata basin involve upstream migration and passive downstream movements of eggs and larvae for dozens of kilometres. At the end of the downstream movements, the fry need marginal lagoons or bays in order for their ...

Acta Oecol, 2005

Studies investigating fish/macrophyte associations in the neotropics are rare. Aquatic vegetation... more Studies investigating fish/macrophyte associations in the neotropics are rare. Aquatic vegetation enhances structural complexity of the environment, potentially influencing predator-prey relationships. The present work characterizes fish assemblages associated with beds of Egeria, a submerged rooted macrophyte, in Rosana Reservoir, Brazil. The main subject of this study was to investigate effects of plant biomass and diel period on fish assemblage attributes (density, total weight, taxa richness and diversity), testing the hypothesis that macrophyte density and diel period greatly influences fish assemblage structure. Fishes were sampled with a 1-m 2 throw trap at morning, midday and dusk, at six sites. The assemblages were primarily composed of small-sized species (e.g. Characiformes) and juveniles, with few large species (Gymnotiformes and Cichlidae). Around 95% of the individuals were captured in habitats with medium and high vegetation biomass. Fish assemblage attributes differed significantly with respect to macrophyte biomass. Highest values of these attributes were observed in maximum plant biomass, in contrast with trends observed in previous works, where higher values (mainly of fish density) were found in intermediate plant coverage. Oxygen, temperature and pH were within normal ranges, therefore, variation in assemblage attributes is assumed to be explained primarily by plant density. No pattern of diel variation was observed, perhaps reflecting sedentary characteristics of these taxa. Results from this study illustrate that procedures to reduce macrophyte density in reservoirs of the Paraná-Tietê-Paranapanema systems, may cause strong alterations in the fish assemblages, resulting in lower fish density, biomass and species richness of taxa utilizing Egeria beds.

Natureza & Conservação, 2015

Craig/Freshwater Fisheries Ecology, 2015

River Research and Applications

Environmental Biology of Fishes

ABSTRACT This study evaluated the relationship between the young of year (YOY) abundance of migra... more ABSTRACT This study evaluated the relationship between the young of year (YOY) abundance of migratory fish species and the interannual variations in the duration and delay of floods in the Upper Paraná River floodplain. YOY of the most abundant migratory species Brycon orbignyanus, Hemisorubim platyrhynchos, Leporinus elongatus, Leporinus macrocephalus, Leporinus obtusidens, Pseudoplatystoma corruscans, Pterodoras granulosus, Prochilodus lineatus, Salminus brasiliensis and Sorubim lima were studied in a stretch of the Paraná river influenced by dams. Multiple regression analyses were performed with flood duration and delay as predictors for YOY abundances. There were differences among the species in the responses to flood duration and delay. The species B. orbignyanus, L. elongatus, L. macrocephalus, L. obtusidens, and P. lineatus exhibited an exponential increase in YOY abundance with flood duration. An exponential decrease in YOY abundance with flood delay was found for most of the studied species. Nevertheless, flood delay and flood duration were significant predictors of YOY abundance for L. elongatus, L. obtusidens, P. corruscans and P. lineatus. For these species, flood delays may result in failure of recruitment because these species migrate early in the season to adjust their energy reserves and their swimming patterns. Therefore, any efforts to preserve migratory fish should consider discharge manipulation from reservoirs upstream of the study areas. It is crucial that reservoirs are operated in such a way that the quantity, duration and timing of water release are compatible with the viability of spawning and the survival of early life stages of migratory fish.

Neotropical Ichthyology

The limiting similarity theory predicts that divergence in the functional traits of native and in... more The limiting similarity theory predicts that divergence in the functional traits of native and introduced species is an essential component in species establishment, as introduced species must occupy a niche that is unoccupied by resident species. On the other hand, the environmental filtering hypothesis predicts convergence between introduced and native species, as both possess traits that make them adapted to the local abiotic environment. Morphology, spatial co-occurrence, diet, feeding selectivity, and niche breadth and overlap of Erythrinidae were evaluated to detect possible mechanisms acting in the coexistence between non-native and native species. Native (Hoplias sp. B and Hoplias cf. malabaricus) and non-native (Hoplerythrinus unitaeniatus and Hoplias mbigua) species presented differences in morphological traits, spatial co-occurrence, diet, selectivity, and niche breadth and overlap. The mechanisms mediating species coexistence seem to vary according to species. The absenc...

Neotropical Ichthyology

Populations show spatial-temporal fluctuations in abundance, partly due to random processes and p... more Populations show spatial-temporal fluctuations in abundance, partly due to random processes and partly due to self-regulatory processes. We evaluated the effects of various external factors on the population numerical abundance of curimba Prochilodus lineatus in the upper Paraná River floodplain, Brazil, over a 19-year period. Panel data analysis was applied to examine the structure of temporal and spatial abundance while controlling auto-regressive processes and spatial non-homogeneity variances that often obscure relationships. As sources of population variation, we considered predation, competition, selected abiotic variables, construction of a dam upstream of the study area, water level and flood intensity during the spawning period. We found that biological interactions (predation and competition) were not significantly related to variations in curimba abundance; specific conductance was a space indicator of abundance, apparently linked to the biology of the species; intensity ...

PloS one, 2017

Climate change and species invasions interact in nature, disrupting biological communities. Based... more Climate change and species invasions interact in nature, disrupting biological communities. Based on this knowledge, we simultaneously assessed the effects of climate change on the native distribution of the Amazonian fish Colossoma macropomum as well as on its invasiveness across river basins of South America, using ecological niche modeling. We used six niche models within the ensemble forecast context to predict the geographical distribution of C. macropomum for the present time, 2050 and 2080. Given that this species has been continuously introduced into non-native South American basins by fish farming activities, we added the locations of C. macropomum farms into the modeling process to obtain a more realistic scenario of its invasive potential. Based on modelling outputs we mapped climate refuge areas at different times. Our results showed that a plenty of climatically suitable areas for the occurrence of C. macropomum occurrence are located outside the original basins at the ...

PloS one, 2017

Cannibalism has been commonly observed in fish from northern and alpine regions and less frequent... more Cannibalism has been commonly observed in fish from northern and alpine regions and less frequently reported for subtropical and tropical fish in more diverse communities. Assuming all else being equal, cannibalism should be more common in communities with lower species richness because the probability of encountering conspecific versus heterospecific prey would be higher. A global dataset was compiled to determine if cannibalism occurrence is associated with species richness and latitude. Cannibalism occurrence, local species richness and latitude were recorded for 4,100 populations of 2,314 teleost fish species. Relationships between cannibalism, species richness and latitude were evaluated using generalized linear mixed models. Species richness was an important predictor of cannibalism, with occurrences more frequently reported for assemblages containing fewer species. Cannibalism was positively related with latitude for both marine and freshwater ecosystems in the Northern Hemis...

Acta Scientiarum Biological Sciences, May 9, 2008

RESUMO. Com o objetivo de avaliar a composição da ictiocenose de lagoas da planície aluvial do al... more RESUMO. Com o objetivo de avaliar a composição da ictiocenose de lagoas da planície aluvial do alto rio Paraná em relação às categorias tróficas, foram realizadas coletas nas lagoas Figueira, Genipapo e Pousada, em março/1999. Após as capturas e obtenção dos dados biométricos, os peixes foram eviscerados e os estômagos fixados em formol 4%. Os conteúdos estomacais foram analisados pelos métodos de freqüência de ocorrência e volumétrico combinados no Índice Alimentar (IAi). Foram amostradas 40 espécies, as quais foram agrupadas em 10 categorias tróficas, ou seja, detritívora, iliófaga, zooplanctófaga, algívora, carcinófaga, piscívora, insetívora, bentófaga, herbívora e onívora. Para a lagoa Pousada, foram importantes, em número, as categorias zooplanctófagas (48,31%), na lagoa Genipapo foram os iliófagos (74,96%), enquanto que para a lagoa Figueira algívoros sobressaíram, com 75,58% da captura, s. Em relação à biomassa, observou-se que detritívoros foram dominantes na lagoa Pousada (45,7%) e lagoa Figueira (27,7%), enquanto que na lagoa Genipapo predominaram os iliófagos (90,0%). Registrou-se alta disponibilidade de camarões nas três lagoas, embora estes tenham sobressaído apenas na dieta dos peixes da lagoa Figueira (20,7%). Embora a maior distância entre as três lagoas seja inferior a 1km, elas são submetidas a diferentes níveis de influência do rio Paraná, e apresentam fisiografias distintas e composições ictiofaunísticas diversas. Além disso, várias espécies icticas apresentam dietas distintas conforme a lagoa considerada, revelando papeis distintos na cadeia trófica desses ambientes. Palavras chave; estrutura trófica, alimentação de peixes, lagoas. ABSTRACT. Trophic characterization of ichthyofauna from three lagoons of the Upper Paraná river floodplain, Brazil. Ichthyofauna from three lagoons of the upper Paraná River floodplain was evaluated according to trophic categories. Samples were obtained in the Figueira, Genipapo, and Pousada lagoons in March 1999. Stomach contents were analyzed according to methods of occurrence and volumetric frequency, combined in an alimentary index (IAi). Forty species were caught and grouped in ten trophic categories (detritivorous, ileophagous, zooplankton-feeder, algivorous, shrimp eater, piscivorous, insectivore, bentophagous, herbivore and omnivore). Zooplankton feeders (48.3%) predominated in the Pousada Lagoon, ileophagous species (74.9%) in the Genipapo Lagoon and algivorous species (75.6%) in the Figueira Lagoon. With regard to biomass, detritivorous predominated in the Pousada (45.7%) and Figueira (27.7%) lagoons, and ileophagous (90.0%) were dominant in the Genipapo Lagoon. Although the distance among lagoons is less than 1 km, the degree of influence from the Paraná river is different, since lagoons have distinct physiography and ichthyofauna composition. Several fish species presented different diets depending on the lagoon and reveal that they play distinct roles in the trophic chain of these environments.

Hydrobiologia, Nov 30, 1998

Base de dados : REPIDISCA. Pesquisa : 48804 [Identificador único]. Referências encontradas : 1 [r... more Base de dados : REPIDISCA. Pesquisa : 48804 [Identificador único]. Referências encontradas : 1 [refinar]. Mostrando: 1 .. 1 no formato [Detalhado]. página 1 de 1, 1 / 1, REPIDISCA, seleciona. para imprimir. Id: 48804. Autor: Agostinho, Angelo A; Gomes, Luiz C. ...

Environ Biol Fish, 1996

Environmental Biology of Fishes 46: 297-307.1996. 0 1996 Kluwer Academic Publishers. Printed in t... more Environmental Biology of Fishes 46: 297-307.1996. 0 1996 Kluwer Academic Publishers. Printed in the Netherlands. ... Feeding styles of five species of bottom-feeding fishes of the high Paran ... Rosemara Fugi, Norma Segatti Hahn & Angelo Antonio Agostinho Nucleo de ...

River Res Appl, 2009

Fish community surveys were conducted in five tributaries of the Corumbá River before and after d... more Fish community surveys were conducted in five tributaries of the Corumbá River before and after damming. Electrofishing samples were collected monthly in the pre-impoundment period (March 1996 to August 1996) and 15 in the post-impoundment period (September 1996 to February 1999). A self-organizing map (SOM, an Artificial Neural Network algorithm) was used to represent the patterns of fish assemblages. Samples collected in both the pre-and post-impoundment periods were randomly dispersed on the SOM, and, therefore, a clear and significant pattern of separation between samples collected during these two time periods was not found. Mean and maximum water depth, which is correlated with ground water level, did not significantly separate the pre-and post-impoundment samples. However, we found significant differences between the two periods for water temperature, pH, conductivity, DO and current velocity, but abundances of fish species (summarized in the clusters identified by the SOM) did not differ significantly. Instead, the validity of the clusters distinguished by the SOM was confirmed by significant differences in some biotic variables: species richness, equitability and log transformed total abundance. Indicator species values identified the most preferred cluster (and respective complex of environmental factors) for a given species. Only one cluster did not contain any significant species indicator values, but it was dominated by samples from the Furnas Stream, which was the only effluent that could be entered by fish from the main river channel after the damming owing to its location below the dam, which has no fish ladder.

Fish Res, 2002

Fishery yields in reservoirs of the Upper Paraná River basin are small when compared to those in ... more Fishery yields in reservoirs of the Upper Paraná River basin are small when compared to those in other parts of the world. Several hypotheses have been formulated to explain the small yields, but low primary production has not been seriously considered as a possibility. In a sample of seven reservoirs, yield was directly related to fishing effort and chlorophyll a concentration; thus, enhancement of these factors may boost yield. However, primary production is difficult to augment in large reservoirs, plus current levels of effort seem to be nearing maximum sustainable yields in some reservoirs, and therefore increased fishing effort is not likely to boost yields to levels recorded in other geographical regions. Low primary production in reservoirs of the Upper Paraná River basin appears to be a result of interactions between physical characteristics of the reservoirs and climatic conditions of the region.

Aquatic Ecosystem Health Management, 2007

River Research and Applications, Apr 30, 2002

The reproductive strategies of potamodromous fish of the Plata basin involve upstream migration a... more The reproductive strategies of potamodromous fish of the Plata basin involve upstream migration and passive downstream movements of eggs and larvae for dozens of kilometres. At the end of the downstream movements, the fry need marginal lagoons or bays in order for their ...

Acta Oecol, 2005

Studies investigating fish/macrophyte associations in the neotropics are rare. Aquatic vegetation... more Studies investigating fish/macrophyte associations in the neotropics are rare. Aquatic vegetation enhances structural complexity of the environment, potentially influencing predator-prey relationships. The present work characterizes fish assemblages associated with beds of Egeria, a submerged rooted macrophyte, in Rosana Reservoir, Brazil. The main subject of this study was to investigate effects of plant biomass and diel period on fish assemblage attributes (density, total weight, taxa richness and diversity), testing the hypothesis that macrophyte density and diel period greatly influences fish assemblage structure. Fishes were sampled with a 1-m 2 throw trap at morning, midday and dusk, at six sites. The assemblages were primarily composed of small-sized species (e.g. Characiformes) and juveniles, with few large species (Gymnotiformes and Cichlidae). Around 95% of the individuals were captured in habitats with medium and high vegetation biomass. Fish assemblage attributes differed significantly with respect to macrophyte biomass. Highest values of these attributes were observed in maximum plant biomass, in contrast with trends observed in previous works, where higher values (mainly of fish density) were found in intermediate plant coverage. Oxygen, temperature and pH were within normal ranges, therefore, variation in assemblage attributes is assumed to be explained primarily by plant density. No pattern of diel variation was observed, perhaps reflecting sedentary characteristics of these taxa. Results from this study illustrate that procedures to reduce macrophyte density in reservoirs of the Paraná-Tietê-Paranapanema systems, may cause strong alterations in the fish assemblages, resulting in lower fish density, biomass and species richness of taxa utilizing Egeria beds.

Natureza & Conservação, 2015

Craig/Freshwater Fisheries Ecology, 2015