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Large tropical rivers are increasingly affected by dam construction, which generally implies alteration of flow regimes, increased water transparency, decline of native species and proliferation of invasive alien species. The potential of native Neotropical piscivores to provide biotic resistance to alien fish invaders and its interaction with water turbidity was investigated through mesocosm experiments. Three invasive and two native fish species were offered as prey to three native piscivores of the Parana river in 1000 L tanks. After 48 h, prey survival was compared among trials with and without the piscivores and in turbid (~ more preserved systems) versus clear water (~ disturbed systems by damming) treatments. Prey survival, particularly of the invasive species, was significantly lower in turbid water in the presence of predators (~ 45.9% versus ~ 53.7% in clear water). Piscivores preyed more on smaller individuals in clear water and on larger preys in turbid water. Although vulnerability to predation was prey-specific, our results support the potential of native piscivores to provide biotic resistance against alien freshwater species. Water turbidity mediated the predator–prey interactions and our results confirm the hypothesis that decreased turbidity caused by dams’ construction can affect predation efficiency of native piscivores and increase the abundance of alien fish.

Neotropical freshwater ecosystems are experiencing a great expansion in the number of invasive species, which is especially alarming since this region harbours 30% of the world’s fish biodiversity with high levels of endemism. We aimed to evaluate the main predictors of peacock basses (Cichla spp.) abundance outside their native range, which are the Amazon and Tocantins-Araguaia river basins. We used multivariate ordination techniques and multimodel inference to analyse peacock basses abundance in twelve reservoirs of the Paraiba do Sul river basin, southeastern Brazil. Interestingly, reservoirs at higher (southernmost) latitudes, located in more populated areas, had higher water temperature and lower turbidity, due to increased water residence time, and these three variables were also positively correlated with abundance of this warm-water invasive fish. Habitat structure was less important in explaining peacock basses abundance, which was not significantly related to biotic factors (fish species richness and time since peacock basses introduction). We hypothesize that the observed effects of reservoir management on limnological features and peacock bass abundance, particularly water residence time (as a mediator of temperature and turbidity), may apply to other Neotropical basins and could influence the impact of this invader.

The Brazilian Environmental Ministry (MMA) released a report in 2016 listing 163 non-native species into Brazilian inland waters. Reservoirs are among the freshwater habitats most frequently associated with the release of non-native species. Therefore, the aim of the present study was to evaluate the occurrence and distribution of the non-native species listed by the MMA, in large Brazilian reservoirs (≥ 30 km2). Further, we have tested the hypothesis that beta diversity of non-native species within reservoirs from the same basin is lower than those among reservoirs from distinct basins. A literature search was performed for 70 Brazilian reservoirs, resulting in the records of 91 non-native species. Reservoirs from the Parana basin showed the highest number of occurrences, with 33 non-native species recorded only in the Itaipu reservoir. Beta diversity of non-native species showed higher variability among reservoirs from different basins than those within the same basin. Some basins were also distinguished by their composition of non-native species, as supported by the IndVal index. Non-native species were widespread along Brazilian reservoirs, and their distribution can be even higher than reported.

The present study aimed to assess corocoro grunt use as bioindicator of Hg contamination in coastal marine systems by testing environmental (seasons) and biological effects (sexual maturity, size and weight) on THg accumulation and assessing human health risk. Fish was captured in winter and summer seasons at Vermelha Beach, Rio de Janeiro, Southeast Brazil. Adult O. ruber showed significantly higher THg than juveniles, and THg concentrations were positively correlated to fish length and weight. Fish THg concentrations did not differ between seasons and were below the accepted limit for human consumption. Human exposure risk by fish consumption was 0.31 μg MeHg kg−1 week−1 and the hazard quotient was 0.44 (0.11–1.84). Our results confirm the applied use of O. ruber as sentinel species for Hg contamination monitoring and highlight concern for its consumption, especially for local fishermen populations that highly consume this fish and may be more susceptible to Hg adverse effects.

This study comprises the first record of a juvenile Giant Devil Ray specimen for Rio de Janeiro, Southeastern Brazil, and its metal and metalloid contents. A scientometric assessment was also performed for the Manta and Mobula genera. Only five records were found, and only As, Cd, Pb, Hg, Pt, Pd and Rh have been assessed. All studies but one concerned human consumption. A significant knowledge gap on metal and metalloid ecotoxicology for mobulid rays is noted, indicating the emergence of a new field of research that th may be applied for wildlife conservation and management in response to anthropogenic contamination. Our study is also the first to provide Al, Cr, Cu, Fe, Mn, Sr, Ti, V and Zn contents for muscle, liver, brain and kidney for a mobulid ray and one of the scarce reports concerning As, Cd, Hg and Pb in muscle, liver and kidney.

Rocky reefs are one of the most important biotopes in Guanabara Bay due to their broad distribution and high species diversity. This study aimed to describe the composition and structure of the fish assemblage associated with rocky reefs in Vermelha Beach (RJ/Brazil), an estuarine-marine transitional zone located at the entrance of Guanabara Bay. Fish were surveyed through underwater visual censuses, conducted by snorkeling divers along 10 m²-linear transects (n = 90). A total of 2.487 fishes were recorded belonging to 29 species in 18 families. Except for Atherinella brasiliensis, all other species are intimately associated with rocky reefs. The present work also stresses the importance of further studies to evaluate the role of periodic influences of estuarine and oceanic waters as structuring factors of the fish assemblages associated with rocky reefs at Vermelha Beach and similar ecosystems.

Made available in DSpace on 2018-11-26T17:16:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-15 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The Abrolhos Bank is an area of high ecological, socio-economic importance and harbour the richest and most extensive coral reefs in the South Atlantic. Here we report the discovery of shallow (12-25 m depth) reef complex with ten large biogenic structures, intermediate between the typical mushroom-shaped pinnacles of the northern Abrolhos Bank (17 degrees-18 degrees S) and the small patch reefs found on the central/southern coast of the Espirito Santo State (19 degrees-20 degrees S). The newly discovered reefs harbour a relatively rich and abundant reef community, with 73 fish and 14 benthic cnidarian species, including endangered and commercially important ones. We discuss on urgent needs of properly mapping and understanding the ecological functioning of this reef system. Information provided here is a baseline for future impact evaluations, particularly considering the recent worst environmental disaster of Brazil from a dam collapse in Doce river that affected the region. (C) 2016 Elsevier Ltd. All rights reserved. Univ Fed Espirito Santo, Dept Oceanog & Ecol, Ave Fernando Ferrari,514 Goiabeiras, Vitoria 29075910, ES, Spain Assoc Ambiental Voz Nat, Vitoria, ES, Spain Univ Fed Estado Rio de Janeiro, Programa Posgrad Ciencias Biol Biodiversidade Neo, Rio De Janeiro, RJ, Brazil Inst Meros Brasil, Curitiba, PR, Brazil Calif Acad Sci, San Francisco, CA 94118 USA Univ Estadual Paulista, Dept Morfol, Inst Biociencias, Botucatu, SP, Brazil Inst COMAR Conservacao Marinha Brasil, Joinville, SC, Brazil Univ Fed Paraiba, Ctr Ciencias Aplicadas & Educ, Rio Tinto, PB, Brazil Univ Fed Espirito Santo, Ctr Univ Norte Espirito Santo, Sao Mateus, ES, Brazil Univ Calif Santa Cruz, Ecol & Evolutionary Biol Dept, Santa Cruz, CA 95064 USA Univ Estadual Paulista, Dept Morfol, Inst Biociencias, Botucatu, SP, Brazil CNPq: GDE 202475/ 2011-5 CNPq: 54515130/2011

Fluctuating asymmetry (FA), which can be defined as random morphologic changes on bilateral symmetry plan of paired morphometric and meristic characters in response of environmental disturbances, is an alternative tool to traditional methods of environmental health assessment that has an interesting potential to appraise the state of adaptation of a population before that acute contaminations affect the whole community or ecosystem. This study aimed to assess the occurrence of FA in three morphometric and three meristic characters of the Corocoro grunt Orthopristis ruber (Cuvier, 1830), and compare the deviations in bilateral symmetry of this reef-associated and omnivorous in Guanabara Bay (Brazil), the venue for various outdoor aquatic sports during the 2016 Olympic Games. Five indexes of FA were tested over the six characters of 66 O. ruber , which were caught during the dry and wet seasons of 2011 and at three areas Guanabara Bay of different environmental characteristics. In addition to validate the existence of FA for O. ruber , our findings revealed significant deviations in the bilateral symmetry according to the FA indexes and fish characters. Together with the FA1 index, the number of gill rakers and the number of rays of the pectoral fin provided the best methodological approach to address the levels of FA in O. ruber as a response to environmental stressors in each region. The levels of FA in O. ruber was significantly lower in the Urca region (less impacted) than for individuals caught near the Paqueta Island and Rio-Niteroi Bridge sites (more degraded). Partial Redundancy Analysis also shows that the fish characters are affected in different ways by environmental stressors, but especially in response to the levels of dissolved oxygen and, secondarily, to water transparency, and that Paqueta Island is apparently less impacted than the site near the Rio-Niteroi Bridge. Our results confirm the potential of FA to be used as a tool to detect environmental effects on a reef-associated fish species in a tropical polluted bay, but further studies are necessary to validate our findings for other species and ecosystems.

Although significantly impacted, Guanabara Bay (GB), located in southeastern Brazil, is still an important fishery source for the state of Rio de Janeiro. Hg contamination, in particular, is of concern in the area and should be regularly monitored, as Hg bioaccumulation and biomagnification processes may lead public health risks to the local human population due to the consumption of contaminated food items, such as crabs. In this context, the aim of the present study was to determine total Hg (THg) concentrations in swimming crabs from three GB areas and investigate the influence of biotic and abiotic factors on Hg concentrations at the beginning and the end of the rainy season. Crabs and water samples were obtained from three areas, inside the bay, at the mouth of the bay and outside the bay. A clear rainfall effect on the investigated abiotic variables was observed, with increased rainfall and temperatures noted at the end of the study period. Significant statistical correlations were observed between THg concentrations and the assessed abiotic variables at the three study points at the beginning and end of the rainy season. The rainy season was noted as directly affecting THg concentrations at Guanabara Bay and, consequently, swimming crab THg contents. THg concentrations in swimming crabs at Urca and at the Cagarras Islands were higher at the beginning of the rainy season compared to the end, while the opposite was observed for the sampling point outside the bay. Higher Hg concentrations were detected at the outermost point of the bay in relation to the Cagarras Islands, probably due to the local upwelling event. THg values in Callinectes sp. were higher than concentrations reported for other areas in Brazil but lower than other reports worldwide. Calculated THg intakes surpassed the maximum National Research Council permissible limits of 0.049 mg/week at all sampling stations during both seasons, raising public health concerns. Further research for longer monitoring periods during different seasons are essential to ascertain which climatic period is most critical regarding Hg availability at this anthropogenically-impacted estuary.

Marine environments are visual domains restricted regarding light characteristics. Overall, blue monochromatic spectrum prevails in offshore areas especially below 15m depth, since long wavelengths are quickly attenuated. Light intensity is even more constrained in coastal waters, particularly those of tropical estuaries and bays, because further scattering through dissolved and suspended materials. Biofluorescence, which is the ability of organisms to absorb light and reflect it in a different wavelength, has been reported for many marine fish. In this paper, biofluorescence was recorded for the first time for the longsnout seahorse Hippocampus reidi, under natural conditions at Ilha Grande bay, Brazil, and both adult, juvenile and fry individuals kept in captivity. Although displaying the same colour emissions, seahorses differed in relation to body lighting, colour patterns, and age wherein fluorescence occurs. Newborn seahorses exhibit green biofluorescence only in the eyes and stomach. Further experiments are necessary to address whether H. reidi can change the patterns of biofluorescence emission for sensorial and social purposes.

This study used the hypervariable domain of the mitochondrial DNA (mtDNA) control region (CR) to assess the genetic divergence among native and invasive populations of Cichla kelberi, which is considered the first peacock cichlid introduced and established throughout Brazil and is among the most invasive populations of this genus worldwide. The maximum likelihood tree based on 53 CR sequences with strong bootstrap support revealed that C. kelberi forms a monophyletic clade, confirming that all 30 C. kelberi studied belong to this morphotype. Additionally, the haplotype analysis of the C. kelberi sequences from 11 sampling sites revealed that invasive populations are much less diverse than native ones and largely dominated by a single haplotype that prevailed in reservoirs at the Paraiba do Sul River basin. Two haplotypes were recorded exclusively in an invasive population at Porto Rico, southern Brazil, and one private haplotype was detected in two reservoirs from Paraiba do Sul (Pereira Passos and Paracambi), suggesting more than one introduction event and that native populations should be better evaluated to encompass the entire genetic diversity of native C. kelberi. The possible route and pathways of C. kelberi introduction are also briefly discussed.

Artificial reefs (ARs) have been used globally to increase fish stocks, especially for local fisheries, but few studies have addressed the seasonal changes in fish attracted to ARs over extended periods. Bottom gillnets were used twice a year (wet versus dry seasons) to investigate how the composition and structure of fishing resources change over seasons during 20 years in the oldest experimental AR complex deployed in Southeastern Brazil. In total, 74 fish species were caught, and Sciaenidae, Carangidae and Ariidae families were the most representative in both numbers and occurrence. Fish abundance, species richness and biomass varied significantly between AR and reference site (RS), with higher values being recorded in the artificial habitats. Generalized additive models and ANOVA showed a gradual transition over time for the fish assemblages associated with the reef complex, indicating an initial phase primarily dominated by estuarine species, followed by an extended period of attraction by reef-associated fish and many species of commercial interest. The season was identified as the most important factor for the development of fish assemblages in the AR complex. Fish abundance increased gradually towards the 14th year after AR deployment and became more variable thereafter, with the stabilization or a abundance decreasing for some species. Our findings reveal that AR might be locally important for commercial species such as Rhizhoprionodon porosus, Macrodon ancylondon and Isopisthus parvipinnis, and highlight the importance of structurally complex structures as a promising strategy to enhance the attraction of fishery resources. JL Lima thanks the Research Foundation of Rio de Janeiro (FAPERJ) and the Coordination for the Improvement of Higher Education Personnel (CAPES) for the PhD scholarship and the internship abroad scholarship, respectively. This work was financed by FAPERJ (E-26/203.002/2016) and by the Brazilian Agency for Research Development - CNPq (301084/2016-5). This study was also partially financed by the CAPES (finance code 001).

Fluctuating asymmetry (FA) is the deviation from perfect bilateral symmetry caused by environmental stresses, developmental instability, and genetic problems during ontogeny. We tested FA levels in larvae of Amphirion ocellaris will change with different salinities (25, 30 and 35), temperatures (20, 25 and 30 °C), and photoperiods (6, 8 and 10 h). A total of 45 larvae of A. ocellaris were analyzed. The survival of larvae did not differ significantly under different salinities (PERMANOVA; F = 0.5, p = 1), temperatures (PERMANOVA; F = 0.8; p = .68) and photoperiods (PERMANOVA; F = 0.13; p = .99). The absence of a significant relationship between FA and survival may have occurred because larvae still have a yolk sac, which justifies the low mortality rate. Eye asymmetry changed significantly among salinities (PERMANOVA; F = 6.02; p = .006), suggesting that the higher salinity (35) was more stressful for A. ocellaris larvaes. Eye asymmetry not changed significantly among temperature (PERMANOVA; F = 1.65; p = .19) and photoperiod (PERMANOVA; F = 1.05; p = .35). For A. ocellaris larvaes it is important to maintain the salinity of 25, due to the better zootechnical performance due to the lower energy expenditure of the species, for osmoregulation. The present work is a pioneer in the detection of AF in the larval eye diameter of A. ocellaris. Fluctuating asymmetry in fish farming has a simple and effective way to detect anomalies that can lead to economic losses.

Toxins synthesized by marine benthic dinoflagellates may be transferred towards higher trophic levels via cell ingestion. Okadaic acid (OA) and other compounds produced by benthic Prorocentrum species are associated with acute and lethal fish responses, but its sublethal effects are barely known. The toxicity of low and intermediate P. lima concentrations to the ringneck blenny Parablennius pilicornis was evaluated through short-term food chain transfer experiments using brine shrimps as primary grazers of toxic cells and, subsequently, as fish prey. Fish activity level, opercular beat frequency, feces biomass, condition factor, and hepatosomatic index were used as toxicity proxies. We hypothesized that sub-lethal concentrations of DSP toxins will affect fish responses, but the strength of these effects will be mediated by the initial somatic condition of exposed individuals. Increased opercular beat frequencies were recorded in fish from the treatment with the highest P. lima concentration provided to brine shrimps, contrasting with rather variable and low opercular beat frequencies from the control. Fish fed with brine shrimps exposed to low and intermediate concentrations of P. lima showed a great inter-individual variation in activity level and particularly in opercular beat frequency, wherein the initial condition factor of exposed individuals appeared to have broadly mediated these fish responses. The presence of P. lima all year round in benthic marine systems highlights a possible chronic exposure of fish to OA and fish will likely become more susceptible to predation in natural environments, facilitating, therefore, toxin transfer through marine trophic webs.

Mercury is an important pollutant, released into aquatic ecosystems both naturally and by anthropogenic action. This element is transferred to aquatic organisms in different ways, causing potential health risks. In addition, mercury can be accumulated by humans, especially through the consumption of contaminated food. This systematic review aims to present mercury pathways, the major routes through which this element reaches the aquatic environment and its transformations until becoming available to living animals, leading to bioaccumulation and biomagnification phenomena. The key biotic and abiotic factors affecting such processes, the impact of mercury on animal and human health and the issue of seafood consumption as a source of chronic mercury contamination are also addressed. A total of 101 articles were retrieved from a standardized search on three databases (PubMed, Emabse, and Web of Science), in addition to 28 other studies not found on these databases but considered fundamental to this review (totaling 129 articles). Both biotic and abiotic factors display fundamental importance in mediating mercurial dynamics, i.e., muscle tropism, and salinity, respectively. Consequently, mercurial contamination in aquatic environments affects animal health, especially the risk of extinction species and also on human health, with methylmercury the main mercury species responsible for acute and chronic symptomatology.

To investigate how variations in the volume of artificial reefs affect the structure and composition of the transient ichthyofauna, reefball-type concrete modules were arranged at 9 m of depth along the northern coast of the state of Rio de Janeiro. The modules were arranged in three configurations, each in triplicate: (1) solitary modules (1 m3), (2) side-by-side modules (2 m3) and (3) modules forming a triangle (3 m3). The surrounding ichthyofauna were sampled in two periods of the year (dry: September 2009 and October 2010; rainy: April 2010 and April 2011) with gillnets to record the richness, species diversity, number of individuals and biomass per volume unit. The total mean values of richness, diversity, number of individuals and biomass did not differ significantly among the reef volumes. However, when these variables were analyzed per standardized volume unit, there was an increase in these variables with the increase in reef volume, considering all the transient ichthyofauna as well as the most representative families, Ariidae and Sciaenidae. A non-metric multidimensional scaling ordination analysis revealed differences in the composition of the ichthyofauna between the sampling periods, dominated by Sciaenidae (Stellifer rastrifer, Paralonchurus brasiliensis, Larimus breviceps and Cynoscion virescens) in the dry period and by Ariidae (Aspistor luniscutis) and Carcharinidae (Rhizoprionodon porosus) in the rainy period. The results suggest that the increase in module size from 1 to 3 m3 may result in slight alterations in the community descriptors, with a decrease in the relative values of richness, diversity and density per standardized volume unit. Furthermore, the effects of the seasonal flow of the Paraiba do Sul River may overlap the effects of reef configuration, mainly in the rainy period with higher flow. The implementation of several dispersed 1 m3 modules seems to be the most favorable configuration to attract transient ichthyofauna, especially Ariidae and Sciaenidae, on the northern coast of the state of Rio de Janeiro.

In Brazil, marine fish farming have minor contribution to the primary sector, but some species have shown great potential, such as the Brazilian mojarra, Eugerres brasilianus. However, larviculture is still a bottleneck due to the lack of protocols supporting survival and performance. Fluctuating Asymmetry (FA), which is the random deviation in bilateral symmetry in response to environmental conditions, can be used as a proxy of fish performance. The main purpose of this study was to evaluate, through microcosms experiments whether the FA levels in larvae of E. brasilianus will change with different temperatures (20 °C, 25° and 30°) and salinities (25, 30 and 35). A total of 92 larvae were analyzed. The Student t-test (p = .53) rejected the occurrence of directional asymmetry and validated the presence of FA in larvae's. The survival of larvae did not differ significantly under different temperatures (PERMANOVA; p = .58) and salinity (p = .68), probably because the early larval stage (i.e. before yolk sac assimilation) and short duration of the experiments. Eye asymmetry changed significantly among temperatures (PERMANOVA; p = .0001), but not with salinity (PERMANOVA; p = .77), revealing that waters ≤20 °C might have adverse effects on the Brazilian mojarra. This species is eurihaline, tolerating a wide range of salinity, explaining thus the null effect of this variable on eye asymmetry. However, eye asymmetry at lower temperatures may reduce the visual acuity of Brazilian mojarra, decreasing, therefore, the individual aptitude for food searching and intake, and affecting thus the zootechnical performance of this species in fish farms.

Publicacoes de 1990 a 2010 sobre o uso de recifes artificiais no manejo da ictiofauna no Brasil foram analisadas para caracterizar o perfil dos pesquisadores e descrever a evolucao temporal da producao cientifica. Dez pesquisadores trabalhando com recifes artificiais aplicados ao manejo de peixes foram registrados, com a maioria conduzindo estudos em areas marinhas rasas da regiao Sudeste . A razao entre a quantidade total de artigos publicados exclusivamente sobre recifes artificiais e o numero total de publicacoes variou consideravelmente entre pesquisadores, de menos 1% ate 100% da producao cientifica dedicada sobre recifes artificiais e peixes. Um total de 31 artigos foi publicado em periodicos cientificos indexados, enquanto 44 publicacoes foram obtidas de veiculos com circulacao limitada (i.e. literatura cinza). Dos artigos cientificos, 25 se referiram ao ambiente marinho enquanto apenas seis focaram sobre recifes continentais, sendo a maioria (86.7%) publicada em revistas com fator de impacto inferior a 2,0. Apesar do aparente incremento na producao de artigos indexados e com fator de impacto apos 2000, nossos resultados enfatizam que estudos cientificos sobre recifes artificiais para o manejo pesqueiro sao recentes no Brasil, exigindo pesquisa adicional para se aproximar dos niveis atingidos pelos paises mais produtivos sobre este tema de pesquisa.

Artificial reefs have barely been used in Neotropical reservoirs (about five studies in three reservoirs), despite their potential as a fishery management tool to create new habitats and also to understand fish ecology. We experimentally assessed how reef material (ceramic, concrete, and PVC) and time modulated fish colonization of artificial reefs deployed in Itaipu Reservoir, a large reservoir of the mainstem Paraná River, Brazil. Fish richness, abundance, and biomass were significantly greater in the reef treatments than at control sites. Among the experimental reefs, ceramic followed by the concrete treatments were the materials most effectively colonized, harboring the majority of the 13 fish species recorded. Although dependent on material type, many of the regularities of ecological successions were also observed in the artificial reefs, including decelerating increases in species richness, abundance, mean individual size, and species loss rates with time and decelerating decreases of species gain and turnover rates. Species composition also varied with material type and time, together with suites of life history traits: more equilibrium species (i.e., fishes of intermediate size that often exhibit parental care and produce fewer but larger offspring) of the Winemiller-Rose model of fish life histories prevailed in later successional stages. Overall, our study suggests that experimental reefs are a promising tool to understand ecological succession of fish assemblages, particularly in tropical ecosystems given their high species richness and low seasonality.

Artificial macrophytes were experimentally deployed in Boadella Reservoir (NE Spain) and assessed for fish use throughout the first 3 months of the 2007 summer drawdown. In total, 1,832 individuals of seven fish species were recorded through visual censuses, with introduced perch Perca fluviatilis being the prevalent species. Fish richness and abundance were significantly higher in artificial macrophytes than in rocky shores and sandy beaches, displaying a unimodal variation through time. P. fluviatilis, Rutilus rutilus and Abramis brama were significantly more abundant in artificial macrophytes than in the other two naturally submersed habitats, where no individuals of these species were recorded. The abundances of Squalius laietanus, Lepomis gibbosus, Micropterus salmoides and Cyprinus carpio were overall greater in artificial macrophytes than in rocky shores but displayed significant habitat × time interactions. A decrease in predation risk was apparently the key-factor of the intensive use of artificial macrophytes by small fish (≤100 mm TL) in Boadella Reservoir, since most species reduced drastically or completely the use of submerged structures when body size increased. This study demonstrates that adding artificial structures mimicking aquatic macrophytes can be an interesting tool to mitigate the adverse effects of water level fluctuations on fish assemblages in structure-less and homogeneous ecosystems, and to understand the mechanisms affecting habitat use and species replacement.

Artificial reefs have been deployed worldwide in shallow marine environments to enhance attraction and capture of fish, but, despite their potential as a fishery management option, few studies addressed whether fish assemblages will change with distance from a reef. We experimentally assessed the relationship between fish abundance and richness to increased distance (0, 25, 100, and 300 m) to reef balls deployed on a flat and homogeneous bottom, 9-m deep, on the north coast of Rio de Janeiro, Southeastern Brazil. A total of thirty fish species was associated with the reefs and the variation in species composition with sampling period or technique did not account for changes in fish assemblages with reef distance. Fish abundance and richness were significantly greater at the nearest distances (0 m and 50 m) to the reefs than at 300 m, but while the first dependent variable decreased exponentially with reef distance the later diminished linearly. Fish responses to reef distance were clearly species-specific and the tomtate ( Haemulon aurolineatum — the dominant species that probably used the reefs for shelter purposes) strongly influenced the exponential decreasing pattern found for the total number of fishes and abundance of Haemulidae. The abundance of the close congener Haemulon steindachneri , and of Chaetodon striatus , Serranus flaviventris and serranid species as a group also decreased, but linearly, with reef distance, probably related to variation in home-range. Acanthurus chirurgus and Scorpaena isthmensis decreased linearly in number with reef distance, probably due to feeding rather than refuge purposes. The abundance of Isopisthus parvipinnis tended to increase with reef distance, suggesting that artificial reefs might be unprofitable for those species less dependent on clear water or structurally complex habitats to obtain refuge or food. Overall, our study indicates that artificial reefs are a promising management tool to enhance fish capture in the oligotrophic waters and structureless bottoms of the north coast of Rio de Janeiro, but with varied rates of success, depending on the target species and fishing distance from the reefs.

El objetivo de este trabajo fue hacer un levantamiento entomofaunístico, en un embalse Tropical, utilizando como organismo indicador al pez Trachelyopterus striatulus. Fue analizada la dieta de 383 T. striatulus, muestreados desde abril de 1999 hasta marzo de 2000. La Frecuencia de presencia y el porcentaje de similitud de Schoener fueron aplicados para analizar la dieta. Para identificar variaciones de la entomofauna entre las estaciones del año y las zonas del embalse fueron aplicadas estadísticas univariadas y multivariadas. La dieta estuvo compuesta principalmente por insectos (92.14%) siendo los más frecuentes (%FO): Hymenoptera (57.90%), Odonata (39.76%), Trichoptera (27.41%), Ephemeroptera (26.25%) y Coleoptera (28.96%). Formicidae fue dominante en todas las estaciones del año, en especial en la primavera, mientras, Trichoptera y Ephemeroptera fueron más consumidos en las demás estaciones del año. En la zona alta, predominaron Trichoptera y Ephemeroptera, mientras en las zonas baja e intermedia predominaron Formicidae y Belostomatidae. T. striatulus presenta potencial como muestreador de la entomofauna contribuyendo para el conocimiento de la biología y ecología de los insectos y la ecología trófica de los organismos acuáticos.The fish Trachelyopterus striatulus (Siluriforms: Auchenipteridae) used to sample insects in a tropical reservoir. The study of aquatic environments is sometimes difficult to do with normal sampling methods that use gears. Insectivorous fishes represent good users of these ecosystems and analyzing the aquatic organisms present in fish stomachs, is an alternative way to determine resource abundance and utilization. In this paper, the potential of Trachelyopterus striatulus as an insect sampler was examined through dietary analyses of 383 individuals caught between April 1999 and March 2000 in Lajes Reservoir, a 30 km² oligotrophic impoundment in Southeast Brazil. We estimated frequency of occurrence and Schoener’s index of similarity. Diet changes among seasons and reservoir zones were addressed with DCA and ANOVA analyses. Its diet was 92.1% insects (ten orders and nine families). Hymenoptera (57.90%), Odonata (39.76%), Trichoptera (27.41%), Ephemeroptera (26.25%) and Coleoptera (28.96%) were the most common groups. Highest insect occurrence and richness were recorded in autumn-summer, a period of greater rainfall and insect activity. Formicidae, the dominant prey item in all seasons, appeared to be especially important in spring, a season marked by shortness of food resources. Trichoptera and Ephemeroptera were the most consumed prey items in the other seasons. Highest insect occurrence and richness were recorded in the middle and upper reservoir zones, respectively. Trichoptera and Ephemeroptera prevailed in the upper zone, where small pristine rivers and tributaries are abundant, whereas Formicidae and Belostomatidae predominated in the lower and middle zones. Because of its abundance in many freshwater ecosystems of Brazil, the ubiquity of insects in its digestive tract and the low level of prey degradation, T. striatulus has potential as an insect sampler of Neotropical reservoirs. However, conventional sampling in Lajes Reservoir is necessary to compare the effectiveness of T. striatulus with other insect sampling methods. Rev. Biol. Trop. 57 (4): 1081-1091. Epub 2009 December 01.

1. Since most of the natural habitats critical for freshwater fish survival have been adversely affected by human disturbance, the effectiveness of artificial structures in providing new and suitable habitats for fish has been increasingly investigated. 2. This paper evaluates the role of artificial structures as fish habitat in a structureless 30 km2 Brazilian reservoir, through underwater surveys conducted monthly from April 1999 to March 2000. 3. In total, 5759 fish in nine species were recorded, but only three cichlid species—one native, Geophagus brasiliensis and two non-native, Cichla kelberi and Tilapia rendalli—showed consistent association with the artificial habitats, suggesting that this family reacts to submerged structures. 4. The absence of fish at control sites compared with high occurrences in sites provided with a physically complex structure suggests that artificial structures can play an important ecological role for cichlids smaller than 150 mm TL, probably related to shelter and/or feeding benefits. 5. The level of structural complexity and position in the water column influenced fish use of artificial structures. C. kelberi was associated with highly complex structures, whereas moderately complex bottom structures were more effective in harbouring G. brasiliensis. Bottom structures are apparently more important than midwater structures in harbouring T. rendalli, but structural complexity seemed to play a secondary role. 6. This study is the first in demonstrating that adding complex artificial structures can expand habitats for small fish (

Cetengraulis edentulus is a broadely distributed engraulid in Southwest Atlantic, currently accounting for the main fish species commercially exploited at Guanabara Bay, Brazil. This study aimed to extend the knowledge on reproduction of C. edentulus at Guanabara Bay and to test whether some descriptors of reproductive activity, especially the gonadosomatic index (GSI), and the index of reproductive activity (IRA) changed among seasons. A total of 978 C. edentulus specimens were retrieved from purse seine commercial landings at Conservas Rubi S.A. company, in São Gonçalo city, RJ. Subsamples of 90-120 individuals were collected from bimonthly yields between July 2010 (winter) and June 2011 (autumn). Most fish were adults (120-170 mm TL), in response to the high selectivity of commercial fisheries. All descriptors indicated a broad spawning period (late winter to spring), peaking in November, suggesting this is the critical period to protect C. edentulus stocks from overfishing at Guanabara Bay. Fecundity averaged 12,720 oocytes and was positively related to fish size, GSI and fullness index, indicating that preserving larger individuals (TL > 160 mm) could contribute significantly to the reproductive success of C. edentulus, since they produce more oocytes. Cetengraulis edentulus é um engraulídeo amplamente distribuído no Atlântico Sudoeste, sendo um importante recurso comercialmente explorado na baía de Guanabara, Brasil. O presente estudo teve como objetivo ampliar o conhecimento sobre a reprodução de C. edentulus na baía de Guanabara e testar quais descritores da atividade reprodutiva, especialmente o índice gonadossomático (IGS) e o índice de atividade reprodutiva (IAR) se modificaram ao longo das estações do ano. Um total de 978 indivíduos de C. edentulus foram capturados pelo método de rede de cerco da frota comercial no cais da empresa Conservas Rubi S.A., na cidade de São Gonçalo, RJ. Subamostras de 90-120 indivíduos de C. edentulus foram coletados bimestralmente durante o período de julho de 2010 (inverno) e junho de 2011 (outono). A maioria dos indivíduos foram adultos (120-170 mm CT), em resposta a alta seletividade das capturas comerciais. Todos os índices indicaram um amplo período reprodutivo (final do inverno e primavera), com pico em novembro, sugerindo que este seria um período crítico para preservar os estoques de C. edentulusda sobrepesca na baía de Guanabara. A fecundidade média foi de 12720 ovócitos e foi positivamente relacionada com tamanho do peixe, IGS e índice de repleção, indicando que preservar maiores indivíduos (CT > 160 mm) poderia contribuir significativamente para o sucesso reprodutivo de C. edentulusna área, visto que esses indivíduos produzem um maior número de ovócitos.

Fish assemblages recorded from August 2010 to July 2013 in two lotic and lentic environments of the Middle Paranć River floodplain were studied in the light of flood and flow pulse variations. Three flood pulses occurred during the period of study, each with a different magnitude, duration and timing. Instead four flow pulses were recorded during this period. The varied hydrological conditions had an influence on the ichthyofauna. The fish species richness in both lentic and lotic habitat was negatively correlated with the maximum water level and fish assemblages were spatially and temporally structured according to their different reproductive strategies. Long- and short-distance migratory species were dominant after the flood pulse of the highest intensity and longest duration, whereas sedentary fish and internal fertilisation prevailed during flow pulses and lower flood pulses. Fish assemblage similarity was generally low between habitats during flood and flow pulses, but increased after those events depending on their magnitude, duration and timing. Apparently, flow pulses would also function like floods, as mechanisms of spatio-temporal structuring of fish assemblages. Journal compilation. Fil: Espínola, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Rabuffetti, Ana Pia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Abrial, Elie. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Amsler, Mario Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Blettler, Martin Cesar Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Paira, Aldo Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Simões, Nadson Ressyé. Universidade Federal Do Sul Da Bahia; Brasil Fil: Santos Das Neves, Luciano. Universidade Federal Do Estado Do Rio de Janeiro; Brasil

This work aimed to assess, through experimental comparisons between free and scuba diving performed in Arraial do Cabo city, RJ, Brazil, the abundances of Scartella cristata e Chaetodon striatus -two reef fish species of contrasting behaviors- in different depth layers of sheltered and exposed rocky reefs. C. striatus was homogeneously distributed through all the depth strata (0-10 m) and scuba diving should be preferred over free diving to assess the abundance of this species at exposed rocky shores, undergoing continuous effects of waves and winds. Both free and scuba diving can be used indistinctly and with no data biases to appraise the abundances of C. striatus in non-turbulent reefs or in shallow zones (i.e., ≤ 5 m) of exposed reefs, and, for S. cristata, in all depth layers (i.e., up to 10 m) of both sheltered and exposed reefs. Although the abundances of S. cristata did not significantly differ between free and scuba diving, contrasting with most previous studies that stressed the risk of the first method to underestimate the abundance of small and cryptic species, it should be considered that the previous experience of the diver and the nature of our study (i.e., focused specifically on a cryptic species) may have contributed to our findings. Further studies are, however, necessary to test our findings in different conditions (i.e., depths, hydrodynamic characteristics, and habitat complexity) and for other tropical reef fish species, in order to increase the truthfulness of underwater visual census and reduce the risk of failure of fish conservation and management programs potentially based on biased data.

O presente trabalho foi baseado em dados pretéritos sobre a dieta natural do lambari-cachorro Oligosarcus hepsetus em um reservatório do Sudeste brasileiro, e com isso foi testada a preferência alimentar desse carnívoro, a partir de experimentos com microcosmos. Os experimentos foram realizados em aquários, em janeiro de 2011. Os predadores foram coletados em um tributário do Rio Paraíba do Sul, enquanto as presas: Tilápia rendalli e o lambari, Astyanax fasciatus, foram adquiridas em pisciculturas. Foi testada a preferência alimentar do lambari-cachorro quanto ao tamanho das presas e às espécies-presa e os resultados foram relacionados com a energia da presa. O lambari-cachorro predou tilápia de menores comprimentos (CT) e alturas do corpo (AC), ao passo que não foi observado um padrão evidente de consumo de lambaris. Nos experimentos com CT padronizado, lambari-cachorro consumiu preferencialmente tilápias a lambaris, enquanto, nos experimentos com AC padronizada, não foram detectadas preferências no consumo por determinada espécie-presa. Diferenças energéticas entre espécies-presa parecem importar menos que diferenças morfológicas na preferência alimentar do lambari-cachorro. This study was based on previously published data on natural diet of the pike characin, Oligosarcus hepsetus in a reservoir at Southeastern Brazil, and thus tested the feeding preference of this carnivore using microcosm experiments. The experiments were conducted in aquariums, in January 2011. Predators were collected in a tributary of the Paraíba do Sul River, while preys: Tilapia rendalli and Astyanax fasciatus were obtained of fish farms. We tested the feeding preference by pike characin in relation to prey size and species, and the results were compared to prey energy. Juvenile pike characin predated preferentially on tilapias with lower body length height, whereas no clear pattern of consumption was observed for lambaris. Tilapias were preferentially predated at experiments with standardized prey body length, whereas no feeding preference was recorded on any prey species at experiments with standardized prey body height. Energetic differences between prey species seem to be less important than morphological differences for the feeding preference of pike characin.

The diet of Cichla monoculus (Bloch & Schneider, 1801) in Lajes's Reservoir, a major impoundment in Rio de Janeiro State, Brazil, was assessed, from fishes collected in 1994,1996 and 1999/2000. Gut contents in individuals was analyzed by the index of relative importance (IRI) which deals with numerical, gravimetrical and frequency of occurrence. Cichla monoculus showed a strong piscivorous habits feeding on Cichlidae, Characidae and Pimelodidae, in decreasing order of importance, with a remarkable cannibalism on young-of-the-year. Others minor items in the diet were Macrobrachium sp. and Odonata. Changes in feeding composition varied with reservoir's zones and seasons, with higher diversity in Autumn and peaks of cannibalism in lower zone during Spring/Summer. Overall, only one third of fish species composition in the reservoir are predated by C. monoculus. Condition factor (k) and fullness index varied closely with higher values in lower zone, and lower records in Winter.

We experimentally examined the predator-prey relationships between juvenile spotted sorubim Pseudoplastystoma corruscans and young-of-the-year invasive and native fish species of the Paraná River basin, Brazil. Three invasive (peacock bass Cichla piquiti, Nile tilapia Oreochromis niloticus, and channel catfish Ictalurus punctatus) and two native (yellowtail tetra Astyanax altiparanae and streaked prochilod Prochilodus lineatus) fish species were offered as prey to P. corruscans in 300 L aquaria with three habitat complexity treatments (0%, 50% and 100% structure-covered). Prey survival was variable through time and among species (C. piquiti < O. niloticus < A. altiparanae < P. lineatus < I. punctatus), depending largely on species-specific prey behavior but also on prey size and morphological defenses. Habitat complexity did not directly affect P. corruscans piscivory but some prey species changed their microhabitat use and shoaling behavior among habitat treatments in predator's presence. Pseudoplatystoma corruscans preyed preferentially on smaller individuals of those invasive species with weak morphological defensive features that persisted in a non-shoaling behavior. Overall, our results contrast with those in a companion experiment using a diurnal predator, suggesting that nocturnal piscivores preferentially prey on different (rather diurnal) fish species and are less affected by habitat complexity. Our findings suggest that recovering the native populations of P. corruscans might help controling some fish species introduced to the Paraná River basin, particularly C. piquiti and O. niloticus, whose parental care is expected to be weak or null at night. A relação predador-presa entre juvenis de pintado Pseudoplatystoma corruscans (piscívoro nativo) e jovens do ano de espécies nativas e invasoras de peixes da bacia do rio Paraná, Brasil, foi testada experimentalmente. Três espécies de peixe invasoras (o tucunaré Cichla piquiti, a tilápia do Nilo Oreochromis niloticus e o bagre do canal Ictalurus punctatus) e duas nativas (o lambari do rabo amarelo Astyanax altiparanae e o curimbatá Prochilodus lineatus) foram oferecidas como presa para P. corruscans em microcosmos, com três tratamentos de complexidade de habitat (0%, 50% e 100% de cobertura por estruturas submersas). A sobrevivência de presas variou ao longo do tempo e entre espécies (C. piquiti < O. niloticus < A. altiparanae < P. lineatus < I. punctatus), sendo governada, em grande parte, por diferenças espécies-específicas no comportamento das presas, mas também pelo tamanho e defesas morfológicas das mesmas. A complexidade de habitat não afetou diretamente a piscivoria de P. corruscans, mas, na presença do predador, algumas espécies-presa alteraram seu comportamento quanto ao uso de micro-habitat e grau de agregação entre os níveis de complexidade de habitat. Pseudoplatystoma corruscans predou preferencialmente sobre os indivíduos menores das espécies invasoras que apresentaram estruturas morfológicas defensivas pouco desenvolvidas e que não formavam cardume. Em geral, os resultados obtidos contrastam com os de um experimento análogo, no qual foi usado um piscívoro diurno, sugerindo que piscívoros noturnos predam preferencialmente sobre espécies de peixes diferentes (de hábitos mais diurnos) e que são menos afetados pela complexidade estrutural de habitats. Os resultados obtidos sugerem que a recuperação de populações nativas de P. corruscans poderia contribuir para o controle de algumas espécies de peixes introduzidas no rio Paraná, especialmente C. piquiti e O. niloticus, dos quais se espera que o cuidado parental seja reduzido ou nulo à noite.

A pesar de ser uno de los peces cíclidos más conocidos por su importancia para la pesca artesanal y deportiva, y entre los más grandes peces en el Neotrópico, los datos sobre la anatomía del tracto digestivo de los pavones (Cichla spp.) están bastante deficientes, especialmente para las poblaciones no nativas. En este trabajo se describe por primera vez la morfología del tracto digestivo de Cichla kelberi, un piscívoro voraz que se introdujo en la década de 1950 en un embalse oligotrófico y físicamente de baja complejidad en Brasil. Los pavones se recogieron entre 1994 y 2002 en el embalse Lajes, con redes de enmalle (25 a 55mm de malla, 20-50x2m), redes de cerco (10x2.5m, 8.0mm de malla), atarrayas y pesca. Todos los peces se mantuvieron en hielo en el campo y luego fueron trasladados al laboratorio, donde fueron identificados, medidos, pesados y disectados para el análisis del tracto digestivo. El Índice de Importancia Relativa, el IIR se calculó para la caracterización de la dieta, mientras que las regresiones lineales y no lineales se realizaron para evaluar los patrones de crecimiento de cuatro caracteres morfológicos relacionados con la alimentación (por ejemplo: ancho de la boca, altura de la boca, longitud del estómago y longitud del intestino) y el número de branquiespinas en la ontogenia en C. kelberi. La mayoría de las estructuras del tracto digestivo estaban directamente relacionadas con la dieta de los piscívoros C. kelberi, lo que indica que el pavón es un depredador diurno, batipelágico y limitado por el tamaño de la boca abierta ya que se alimenta en gran medida de presas en aguas poco profundas de la zona litoral. El ancho de la boca y la altura tuvieron un crecimiento alométrico (b > 1) con el tamaño de pavones, y se amplió el rango de tamaño en el que las presas se pueden ser comidas, pero sobre todo para los depredadores menores de ~400mm de longitud total. A diferencia, las longitudes del estómago y el intestino aumentaron isométricamente (b=1), lo que podría limitar el consumo de presas para adultos de C. kelberi, especialmente aquellos en etapas avanzadas de la maduración gonadal. La presencia de branquiespinas marcadas, agudas y furcadas en C. kelberi puede estar relacionada con un incremento en la retención de presas en los recursos limitados del embalse Lajes, pero son necesarios más estudios si tales características son desencadenadas al azar por anomalías genéticas o fenotípicas, o efectivamente son una ventaja ecológica para el depredador. Además de contribuir con el mejoramiento del conocimiento biológico actual en los pavones, nuestros resultados también pueden ser útiles para estudiar si las características morfológicas relacionadas con la alimentación van a cambiar con las transiciones en el consumo de presas por C. kelberi y/o con las condiciones particulares del ecosistema invadido.

The study of aquatic environments is sometimes difficult to do with normal sampling methods that use gears. Insectivorous fishes represent good users of these ecosystems and analyzing the aquatic organisms present in fish stomachs, is an alternative way to determine resource abundance and utilization. In this paper, the potential of Trachelyopterus striatulus as an insect sampler was examined through dietary analyses of 383 individuals caught between April 1999 and March 2000 in Lajes Reservoir, a 30 km2 oligotrophic impoundment in Southeast Brazil. We estimated frequency of occurrence and Schoener's index of similarity. Diet changes among seasons and reservoir zones were addressed with DCA and ANOVA analyses. Its diet was 92.1% insects (ten orders and nine families). Hymenoptera (57.90%), Odonata (39.76%), Trichoptera (27.41%), Ephemeroptera (26.25%) and Coleoptera (28.96%) were the most common groups. Highest insect occurrence and richness were recorded in autumn-summer, a period of greater rainfall and insect activity. Formicidae, the dominant prey item in all seasons, appeared to be especially important in spring, a season marked by shortness of food resources. Trichoptera and Ephemeroptera were the most consumed prey items in the other seasons. Highest insect occurrence and richness were recorded in the middle and upper reservoir zones, respectively. Trichoptera and Ephemeroptera prevailed in the upper zone, where small pristine rivers and tributaries are abundant, whereas Formicidae and Belostomatidae predominated in the lower and middle zones. Because of its abundance in many freshwater ecosystems of Brazil, the ubiquity of insects in its digestive tract and the low level of prey degradation, T. striatulus has potential as an insect sampler of Neotropical reservoirs. However, conventional sampling in Lajes Reservoir is necessary to compare the effectiveness of T. striatulus with other insect sampling methods.

Invasion by Cichla ocellaris was studied in the Upper Paraná River floodplain. Generalised linear models and the Akaike Information Criterion (AIC) were applied to standardised gill-net catch data (CPUE), with years, rivers, secchi depth, and their respective interactions. Generalised additive models and AIC were used to evaluate relationships of CPUE for C. ocellaris with standard length, sampling year and secchi depth. C. ocellaris was first recorded in 1992 in the Paraná and Ivinheima Rivers. Nevertheless, the CPUE of individuals was very low in the latter until 2000, and the species was not recorded from the Baía River until 2000. In 2001, CPUE of C. ocellaris greatly increased (from 20 to 140) in all three rivers, and this coincided with changes in hydrology and suspended sediment. Greater secchi depth is thought to benefit foraging by these visually oriented, diurnal piscivores. The estimated annual growth rate for local populations was 21% for the Paraná, 42% for the Ivinheima, and 73% for the Baía Rivers. Consequently, relative to other populations, C. ocellaris of the Baía River and, to a lesser degree, the Ivinheima River, appear to be less influenced by density-dependent factors given their more recent invasions of those areas.

Effects of water level fluctuations on body condition of Geophagus brasiliensis were studied in a 30 km² Brazilian oligotrophic reservoir. Physiological condition (K) and gonadosomatic index (GSI) were compared according to water level (low and high). Females' best conditions were associated to higher resources availability during high water, since gonad development did not change between low and high water. Males' condition did not change between water levels, while the highest gonad development occurred in low water. Females presented higher reproductive investment than males, which allocated most of energy for somatic development. This strategy could be a mechanism to undergo the stress caused by oligotrophic characteristics of the reservoir enhanced during low water level. Efeitos do nível da água na condição de Geophagus brasiliensis foram analisados em um reservatório oligotrófico. A condição fisiológica (K) e o índice gonadossomático (IGS) foram comparados entre os níveis da água (baixo e alto). Melhores condições de fêmeas foram associadas a maiores disponibilidades de recursos no nível alto, já que o desenvolvimento gonadal não variou. Não foram registradas diferenças na condição de machos, contudo maiores valores de IGS ocorreram no nível baixo. Fêmeas apresentaram elevado investimento reprodutivo, enquanto machos investiram mais no desenvolvimento somático. Tal estratégia pode ser um mecanismo para suportar o estresse causado pelas características oligotróficas do reservatório, intensificadas durante o período de níveis baixos da água.

C. edentulus accounts for the major fishery resource in Guanabara Bay, but there are only few studies about its captures.This study analyzed the long term changes on C. edentulus catches in Guanabara Bay, focusing especially on temporal variation on capture effort, boat storage temperature, and fish price and size.We assessed the 2002-2011 database of fish landings at the pier of Rubi S.A., with records of year, month, total catch (kg), number of fish per kg, boat storage temperature (oC), and price per kg to boat owner (US$). Those variables differed among years and months (ANOVA; p

The diet of Cichla monoculus (Bloch & Schneider, 1801) in Lajes's Reservoir, a major impoundment in Rio de Janeiro State, Brazil, was assessed, from fishes collected in 1994,1996 and 1999/2000. Gut contents in individuals was analyzed by the index of relative importance (IRI) which deals with numerical, gravimetrical and frequency of occurrence. Cichla monoculus showed a strong piscivorous habits feeding on Cichlidae, Characidae and Pimelodidae, in decreasing order of importance, with a remarkable cannibalism on young-of-the-year. Others minor items in the diet were Macrobrachium sp. and Odonata. Changes in feeding composition varied with reservoir's zones and seasons, with higher diversity in Autumn and peaks of cannibalism in lower zone during Spring/Summer. Overall, only one third of fish species composition in the reservoir are predated by C. monoculus. Condition factor (k) and fullness index varied closely with higher values in lower zone, and lower records in Winter.

We tested the predator-prey relationships between a native piscivore (Salminus brasiliensis) and introduced and native fish species of the ParanaRiver, Brazil. We hypothesised that S. brasiliensis can exert biotic resistance against invasive fishes but not at the same degree for all species. Three invasive (Cichla piquiti, Oreochromis niloticus and Ictalurus punctatus) and two native (Astyanax altiparanae and Prochilodus lineatus) species were offered as prey to S. brasiliensisin 300Laquaria trials atthree levels of cover(0%, 50% and100% of artificial macrophytes).S. brasiliensis hadagreaterabilitytocapturepreyincomplexhabitats,sopredationsuccessdidnotdecreasewithhabitatcomplexityand evenincreasedonI.punctatus.Preysurvivalwasvariablethroughtimeandamongspecies,beinghighforI.punctatus.The three most consumed species (P. lineatus, C. piquiti, and O. niloticus) were less active and occupied the aquaria surfaces, changing strongly their behaviour with habitat complexity. Except for P. lineatus and C. piquiti,S. brasiliensis preferably preyed on smaller individuals of the other species. Our experiments support that S. brasiliensis is an interesting candidate to resist the invasion by C. piquiti and O. niloticus but not to control the abundance of I. punctatus. Additional keywords: biotic resistance, invasive species, ParanaRiver basin, predator-prey interactions, Salminus brasiliensis.