First record of cannibalism in the giant mottled eel Anguilla marmorata (Actinopterygii: Anguilliformes) as revealed by DNA barcoding

ABSTRACT Although the giant mottled eel, Anguilla marmorata Quoy & Gaimard, 1824, is widely distributed in the Indo-Pacific region, few ecological studies have been conducted on the species. We investigated the stomach contents of A. marmorata visually and used the DNA-barcode region of the mitochondrial cytochrome c oxidase subunit 1 (CO1) to confirm the species identification. The stomach content analysis revealed that teleosts and crustaceans are the major prey items of A. marmorata. Interestingly, the stomach content of one of the specimens, which was 1029 mm in total length (TL), contained an eel-like fish identified as A. marmorata measuring 510 mm in TL. This study is the first to record cannibalism in the diet of A. marmorata. Although the diet of anguillid eels is generally selective for a single prey species, larger eels are more likely to adopt a diverse feeding habit that includes cannibalism in the tropical river ecosystems.

First record of cannibalism in the giant mottled eel Anguilla marmorata (Actinopterygii: Anguilliformes) as revealed by DNA barcoding

Although the giant mottled eel, Anguilla marmorata Quoy & Gaimard, 1824, is widely distributed in the Indo-Pacific region, few ecological studies have been conducted on the species. We investigated the stomach contents of A. marmorata visually and used the DNA-barcode region of the mitochondrial cytochrome c oxidase subunit 1 (CO1) to confirm the species' identification. The stomach content analysis revealed that teleosts and crustaceans are the major prey items of A. marmorata. Interestingly, the stomach content of one of the specimens, which was 1029 mm in total length (TL), contained an eel-like fish identified as A. marmorata measuring 510 mm in TL. This study is the first to record cannibalism in the diet of A. marmorata. Although the diet of anguillid eels is generally selective for a single prey species, larger eels are more likely to adopt a diverse feeding habit that includes cannibalism in the tropical river ecosystems.(AU)

First record of cannibalism in the giant mottled eel Anguilla marmorata (Actinopterygii: Anguilliformes) as revealed by DNA barcoding

Although the giant mottled eel, Anguilla marmorata Quoy & Gaimard, 1824, is widely distributed in the Indo-Pacific region, few ecological studies have been conducted on the species. We investigated the stomach contents of A. marmorata visually and used the DNA-barcode region of the mitochondrial cytochrome c oxidase subunit 1 (CO1) to confirm the species identification. The stomach content analysis revealed that teleosts and crustaceans are the major prey items of A. marmorata. Interestingly, the stomach content of one of the specimens, which was 1029 mm in total length (TL), contained an eel-like fish identified as A. marmorata measuring 510 mm in TL. This study is the first to record cannibalism in the diet of A. marmorata. Although the diet of anguillid eels is generally selective for a single prey species, larger eels are more likely to adopt a diverse feeding habit that includes cannibalism in the tropical river ecosystems.(AU)

Feeding ecology of electric eel Electrophorus varii (Gymnotiformes: Gymnotidae) in the Curiaú River Basin, Eastern Amazon

In this study, the composition of the diet and the feeding activity of Electrophorus varii were evaluated. The influence of ontogeny and seasonality in these feeding parameters was also examined. Fish were collected in the Curiaú River Basin, Amazon, Brazil, from March 2005 to February 2006, during the rainy (January-June) and dry (July-December) seasons. Diet composition was characterized based on the analysis of stomach contents and feeding dynamics was assessed based on the Stomach Fullness Index (IR) calculated using stomach weight. Stomach content and RI data were grouped into four-cm size classes (40-80, 80-120, 120-160, and 160-200) and two seasonal periods (rainy and dry). The influence of ontogeny and seasonality in the diet was investigated through PERMANOVA, and in the food dynamics through ANOVA. The analysis of stomach contents revealed that fish were the most consumed preys by electric eels, especially Callichthyidae and Cichlidae. Diet composition and RI values of electric eels were not influenced by ontogeny and seasonality. Electric eels are fish predators, regardless of size class and seasonal period.(AU)

Neste estudo foram avaliadas a composição da dieta e a atividade alimentar de Electrophorus varii. A influência da ontogenia e da sazonalidade nestes aspectos da alimentação dos poraquês também foi examinada. Os peixes foram coletados na Bacia do rio Curiaú, Amazônia, Brasil, no período de março de 2005 a fevereiro de 2006, abrangendo os períodos chuvoso (janeiro-junho) e o seco (julho-dezembro). A dieta foi avaliada por meio da análise dos conteúdos estomacais e a dinâmica alimentar por meio do Índice de Repleção Estomacal (RI) baseado nos dados de peso do estômago. Os dados do conteúdo estomacal e do RI foram agrupados em quatro classes de tamanho em cm (40-80, 80-120, 120-160 e 160-200) e dois períodos sazonais (chuvoso e seco). A influência da ontogenia e da sazonalidade na dieta foi investigada por meio da PERMANOVA, e na dinâmica alimentar por meio da ANOVA. A análise do conteúdo estomacal mostrou que os peixes foram as presas mais consumidas pelos poraquês, especialmente Callichthyidae e Cichlidae. A composição da dieta e os valores de RI dos poraquês não foram influenciadas pela ontogenia e pela sazonalidade. Os poraquês são predadores piscívoros, independente da classe de tamanho e do período sazonal.(AU)

Feeding ecology of electric eel Electrophorus varii (Gymnotiformes: Gymnotidae) in the Curiaú River Basin, Eastern Amazon

In this study, the composition of the diet and the feeding activity of Electrophorus varii were evaluated. The influence of ontogeny and seasonality in these feeding parameters was also examined. Fish were collected in the Curiaú River Basin, Amazon, Brazil, from March 2005 to February 2006, during the rainy (January-June) and dry (July-December) seasons. Diet composition was characterized based on the analysis of stomach contents and feeding dynamics was assessed based on the Stomach Fullness Index (IR) calculated using stomach weight. Stomach content and RI data were grouped into four-cm size classes (40-80, 80-120, 120-160, and 160-200) and two seasonal periods (rainy and dry). The influence of ontogeny and seasonality in the diet was investigated through PERMANOVA, and in the food dynamics through ANOVA. The analysis of stomach contents revealed that fish were the most consumed preys by electric eels, especially Callichthyidae and Cichlidae. Diet composition and RI values of electric eels were not influenced by ontogeny and seasonality. Electric eels are fish predators, regardless of size class and seasonal period.(AU)

Neste estudo foram avaliadas a composição da dieta e a atividade alimentar de Electrophorus varii. A influência da ontogenia e da sazonalidade nestes aspectos da alimentação dos poraquês também foi examinada. Os peixes foram coletados na Bacia do rio Curiaú, Amazônia, Brasil, no período de março de 2005 a fevereiro de 2006, abrangendo os períodos chuvoso (janeiro-junho) e o seco (julho-dezembro). A dieta foi avaliada por meio da análise dos conteúdos estomacais e a dinâmica alimentar por meio do Índice de Repleção Estomacal (RI) baseado nos dados de peso do estômago. Os dados do conteúdo estomacal e do RI foram agrupados em quatro classes de tamanho em cm (40-80, 80-120, 120-160 e 160-200) e dois períodos sazonais (chuvoso e seco). A influência da ontogenia e da sazonalidade na dieta foi investigada por meio da PERMANOVA, e na dinâmica alimentar por meio da ANOVA. A análise do conteúdo estomacal mostrou que os peixes foram as presas mais consumidas pelos poraquês, especialmente Callichthyidae e Cichlidae. A composição da dieta e os valores de RI dos poraquês não foram influenciadas pela ontogenia e pela sazonalidade. Os poraquês são predadores piscívoros, independente da classe de tamanho e do período sazonal.(AU)

Bite force, cranial morphometrics and size in the fishing bat Myotis vivesi (Chiroptera: Vespertilionidae)

Abstract Fish-eating in bats evolved independently in Myotis vivesi (Vespertillionidae) and Noctilio leporinus (Noctilionidae). We compared cranial morphological characters and bite force between these species to test the existence of evolutionary parallelism in piscivory. We collected cranial distances of M. vivesi, two related insectivorous bats (M. velifer and M. keaysi), two facultatively piscivorous bats (M. daubentonii and M. capaccinii), and N. leporinus. We analyzed morphometric data applying multivariate methods to test for differences among the six species. We also measured bite force in M. vivesi and evaluated if this value was well predicted by its cranial size. Both piscivorous species were morphologically different from the facultatively piscivorous and insectivorous species, and skull size had a significant contribution to this difference. However, we did not find morphological and functional similarities that could be interpreted as parallelisms between M. vivesi and N. leporinus. These two piscivorous species differed significantly in cranial measurements and in bite force. Bite force measured for M. vivesi was well predicted by skull size. Piscivory in M. vivesi might be associated to the existence of a vertically displaced temporal muscle and an increase in gape angle that allows a moderate bite force to process food.(AU)

Resumen La alimentación por peces en murciélagos evolucionó independientemente en Myotis vivesi (Vespertilionidae) y Noctilio leporinus (Phyllostomidae). En este estudio se compararon características craneales morfológicas y fuerza de mordida entre estas especies, para probar la existencia de paralelismo evolucionario en piscivoría. Se recolectaron distancias craneales en M. vivesi, dos parientes insectívoros (M. velifer y M. keaysi), dos murciélagos piscívoros facultativos (M. daubentonii y M. capaccinii), y N. leporinus. Se analizaron datos morfométricos aplicando múltiples métodos para probar las diferencias entre las seis especies. Se midió la fuerza de mordida en M. vivesi y se evalúo si puede ser predicha por el tamaño del cráneo. Las especies piscívoras fueron morfológicamente diferentes de las facultativamente piscívoras y las insectívoras, el tamaño del cráneo tuvo una contribución significativa en esta diferencia. Sin embargo, no encontramos semejanzas morfológicas y funcionales que puedan ser interpretadas como paralelismos entre M. vivesi y N. leporinus. Estas dos especies piscívoras difieren significativamente en medidas craneales y fuerza de mordida. La fuerza de mordida en M. vivesi fue efectivamente predicha por el tamaño de cráneo. La piscivoría en M. vivesi puede estar asociada con la existencia de un músculo temporal verticalmente desplazado y el incremento en el ángulo de apertura mandibular que permite moderar la fuerza de mordida para procesar el alimento.(AU)

Habitat complexity does not influence prey consumption in an experimental three-level trophic chain

Habitat complexity influences species diversity and regulates trophic interactions, mostly by increasing resource partitioning within habitats and providing refuge for prey. The influence of habitat complexity on more than two trophic levels is not well understood, mainly because behavioral modifications of prey and predator may influence the outcome of trophic interactions. Thus, we conducted a two-factor experiment with a three-level trophic chain: a piscivorous fish [Hoplerythrinus unitaeniatus (Spix & Agassiz 1829)], an invertivorous fish (Moenkhausia forestii Benine, Mariguela & C. de Oliveira, 2009) and an aquatic macroinvertebrate (Chironomidae larvae). We measured prey consumption in low, intermediate and high habitat complexity, provided by submerged macrophyte densities, in the presence and the absence of the piscivore, intending to test the hypothesis that higher habitat complexities decrease predators foraging success in different trophic levels. We calculated the percentage of consumed prey in all treatment combinations. There was no significant effect of habitat complexity on prey consumption for neither the piscivorous nor the invertivorous fish, but a positive correlation was found between the percentages of consumed prey by both the piscivore and the invertivore. Observed modifications in the foraging behavior of the piscivore may have resulted in similar prey consumptions in low and high macrophyte densities. Moreover, more active M. forestii could have suffered a higher predation pressure by H. unitaeniatus, resulting in the positive correlation found. We conclude that behavior patterns in different habitat complexities possibly influenced predation rates in the three experimental trophic levels.

A complexidade de habitat influencia a diversidade de espécies e regula interações tróficas, principalmente por possibilitar a partição de recurso nos habitats e fornecer refúgio para presas. A influência da complexidade de habitat sob mais de dois níveis tróficos não é bem compreendida, especialmente porque modificações comportamentais das presas e dos predadores podem influenciar o resultado das interações tróficas. Assim, nós conduzimos um experimento bifatorial com uma cadeia trófica de três níveis: um peixe piscívoro [Hoplerythrinus unitaeniatus (Spix & Agassiz 1829)], um peixe invertívoro (Moenkhausia forestii Benine, Mariguela & C. de Oliveira, 2009) e um macroinvertebrados aquático (larvas de Chironomidae). Mensuramos o consumo de presas em complexidades de habitat baixa, intermediária e alta, dada por diferentes densidades de macrófitas submersas, na presença e ausência do piscívoro, com o intuito de testar a hipótese de que complexidades de habitat mais altas diminuem o sucesso de forrageio de predadores em diferentes níveis tróficos. Calculamos a porcentagem de presas consumidas em todas as combinações de tratamentos. Não houve efeito significativo da complexidade de habitat no consumo de presas para o peixe piscívoro nem para o peixe invertívoro, mas uma correlação positiva foi encontrada entre as porcentagens de presas consumidas pelo piscívoro e pelo invertívoro. Modificações observadas no comportamento de forrageio do piscívoro podem ter resultado em consumo de presas similar em densidades baixas e altas de macrófitas. Além disso, indivíduos de M. forestii com maior taxa de forrageamento podem ter sofrido maior pressão de predação por H. unitaeniatus, resultando na correlação positiva encontrada. Concluímos que padrões comportamentais em diferentes complexidades de habitat possivelmente influenciaram as taxas de predação nos três níveis tróficos experimentais.

Habitat complexity does not influence prey consumption in an experimental three-level trophic chain

ABSTRACT Habitat complexity influences species diversity and regulates trophic interactions, mostly by increasing resource partitioning within habitats and providing refuge for prey. The influence of habitat complexity on more than two trophic levels is not well understood, mainly because behavioral modifications of prey and predator may influence the outcome of trophic interactions. Thus, we conducted a two-factor experiment with a three-level trophic chain: a piscivorous fish [Hoplerythrinus unitaeniatus (Spix & Agassiz 1829)], an invertivorous fish (Moenkhausia forestii Benine, Mariguela & C. de Oliveira, 2009) and an aquatic macroinvertebrate (Chironomidae larvae). We measured prey consumption in low, intermediate and high habitat complexity, provided by submerged macrophyte densities, in the presence and the absence of the piscivore, intending to test the hypothesis that higher habitat complexities decrease predators foraging success in different trophic levels. We calculated the percentage of consumed prey in all treatment combinations. There was no significant effect of habitat complexity on prey consumption for neither the piscivorous nor the invertivorous fish, but a positive correlation was found between the percentages of consumed prey by both the piscivore and the invertivore. Observed modifications in the foraging behavior of the piscivore may have resulted in similar prey consumptions in low and high macrophyte densities. Moreover, more active M. forestii could have suffered a higher predation pressure by H. unitaeniatus, resulting in the positive correlation found. We conclude that behavior patterns in different habitat complexities possibly influenced predation rates in the three experimental trophic levels.

RESUMO A complexidade de habitat influencia a diversidade de espécies e regula interações tróficas, principalmente por possibilitar a partição de recurso nos habitats e fornecer refúgio para presas. A influência da complexidade de habitat sob mais de dois níveis tróficos não é bem compreendida, especialmente porque modificações comportamentais das presas e dos predadores podem influenciar o resultado das interações tróficas. Assim, nós conduzimos um experimento bifatorial com uma cadeia trófica de três níveis: um peixe piscívoro [Hoplerythrinus unitaeniatus (Spix & Agassiz 1829)], um peixe invertívoro (Moenkhausia forestii Benine, Mariguela & C. de Oliveira, 2009) e um macroinvertebrados aquático (larvas de Chironomidae). Mensuramos o consumo de presas em complexidades de habitat baixa, intermediária e alta, dada por diferentes densidades de macrófitas submersas, na presença e ausência do piscívoro, com o intuito de testar a hipótese de que complexidades de habitat mais altas diminuem o sucesso de forrageio de predadores em diferentes níveis tróficos. Calculamos a porcentagem de presas consumidas em todas as combinações de tratamentos. Não houve efeito significativo da complexidade de habitat no consumo de presas para o peixe piscívoro nem para o peixe invertívoro, mas uma correlação positiva foi encontrada entre as porcentagens de presas consumidas pelo piscívoro e pelo invertívoro. Modificações observadas no comportamento de forrageio do piscívoro podem ter resultado em consumo de presas similar em densidades baixas e altas de macrófitas. Além disso, indivíduos de M. forestii com maior taxa de forrageamento podem ter sofrido maior pressão de predação por H. unitaeniatus, resultando na correlação positiva encontrada. Concluímos que padrões comportamentais em diferentes complexidades de habitat possivelmente influenciaram as taxas de predação nos três níveis tróficos experimentais.

Habitat complexity does not influence prey consumption in an experimental three-level trophic chain

Habitat complexity influences species diversity and regulates trophic interactions, mostly by increasing resource partitioning within habitats and providing refuge for prey. The influence of habitat complexity on more than two trophic levels is not well understood, mainly because behavioral modifications of prey and predator may influence the outcome of trophic interactions. Thus, we conducted a two-factor experiment with a three-level trophic chain: a piscivorous fish [Hoplerythrinus unitaeniatus (Spix & Agassiz 1829)], an invertivorous fish (Moenkhausia forestii Benine, Mariguela & C. de Oliveira, 2009) and an aquatic macroinvertebrate (Chironomidae larvae). We measured prey consumption in low, intermediate and high habitat complexity, provided by submerged macrophyte densities, in the presence and the absence of the piscivore, intending to test the hypothesis that higher habitat complexities decrease predators foraging success in different trophic levels. We calculated the percentage of consumed prey in all treatment combinations. There was no significant effect of habitat complexity on prey consumption for neither the piscivorous nor the invertivorous fish, but a positive correlation was found between the percentages of consumed prey by both the piscivore and the invertivore. Observed modifications in the foraging behavior of the piscivore may have resulted in similar prey consumptions in low and high macrophyte densities. Moreover, more active M. forestii could have suffered a higher predation pressure by H. unitaeniatus, resulting in the positive correlation found. We conclude that behavior patterns in different habitat complexities possibly influenced predation rates in the three experimental trophic levels.(AU)

A complexidade de habitat influencia a diversidade de espécies e regula interações tróficas, principalmente por possibilitar a partição de recurso nos habitats e fornecer refúgio para presas. A influência da complexidade de habitat sob mais de dois níveis tróficos não é bem compreendida, especialmente porque modificações comportamentais das presas e dos predadores podem influenciar o resultado das interações tróficas. Assim, nós conduzimos um experimento bifatorial com uma cadeia trófica de três níveis: um peixe piscívoro [Hoplerythrinus unitaeniatus (Spix & Agassiz 1829)], um peixe invertívoro (Moenkhausia forestii Benine, Mariguela & C. de Oliveira, 2009) e um macroinvertebrados aquático (larvas de Chironomidae). Mensuramos o consumo de presas em complexidades de habitat baixa, intermediária e alta, dada por diferentes densidades de macrófitas submersas, na presença e ausência do piscívoro, com o intuito de testar a hipótese de que complexidades de habitat mais altas diminuem o sucesso de forrageio de predadores em diferentes níveis tróficos. Calculamos a porcentagem de presas consumidas em todas as combinações de tratamentos. Não houve efeito significativo da complexidade de habitat no consumo de presas para o peixe piscívoro nem para o peixe invertívoro, mas uma correlação positiva foi encontrada entre as porcentagens de presas consumidas pelo piscívoro e pelo invertívoro. Modificações observadas no comportamento de forrageio do piscívoro podem ter resultado em consumo de presas similar em densidades baixas e altas de macrófitas. Além disso, indivíduos de M. forestii com maior taxa de forrageamento podem ter sofrido maior pressão de predação por H. unitaeniatus, resultando na correlação positiva encontrada. Concluímos que padrões comportamentais em diferentes complexidades de habitat possivelmente influenciaram as taxas de predação nos três níveis tróficos experimentais.(AU)

Size-related and seasonal changes in the diet of the non-native Cichla kelberi Kullander & Ferreira, 2006 in a lowland reservoir in the southeastern Brazil / Mudanças sazonais e relacionadas ao tamanho da dieta do não-nativo Cichla kelberi Kullander & Ferreira, 2006 em um reservatório de planície no sudeste do Brasil

Abstract: We examined size-related and seasonal changes in the diet of the peacock bass Cichla kelberi in a tropical lowland reservoir in southeastern Brazil over three hydro-climatic seasons: summer (high rainfall and temperature), winter (low rainfall and temperature), and late spring (increasing rainfall and temperature) during two years (2006-2007). The tested hypothesis is that this non-native predator fish changes diet during the subadult and adult phases and among seasons to adapt in new colonized environment. Fishes of the families Clupeidae (Platanichthys platana), Characidae (Astyanax spp.) and Cichlidae (Cichla kelberi) were the most important food items, followed by insects of the order Odonata. Cannibalism was also recorded for the largest individuals. A significant size-related change in diet was found with the smallest individuals (Total Length, TL < 20 cm) preying mainly on fishes, whereas the larger individuals (TL > 30 cm) preyed mainly on Odonata. The niche breadth increased during growth, with the largest individuals having a diet more evenly distributed among the available resources. No significant seasonal differences in diet composition were found, but stomachs with higher degree of volume occupied by food were more frequent in late spring than in summer. Conversely, the highest niche breadth was found during the summer compared to the other seasons. Together, these observations suggest an efficient use of the available resources by this top predator in this new colonized system.

Resumo: Foram examinadas as mudanças sazonais na dieta e relacionadas ao tamanho para o tucunaré Cichla kelberi em um reservatório tropical de várzeas no Sudeste do Brasil em três ciclos hidrológicos: verão (elevadas precipitações e temperaturas), inverno (baixas precipitações e temperaturas), e final da primavera (aumentos das precipitações e temperaturas) durante dois anos (2006-2007). A hipótese testada é que este peixe predador não-nativo muda a dieta durante as fases adulta e subadulta e entre as estações do ano para se adaptar neste novo ambiente colonizado. Peixes das famílias Clupeidae (Platanichthys platana), (Characidae (Astyanax spp.) e Cichlidae (Cichla kelberi) foram os itens alimentares mais importantes, seguidos por insetos da ordem Odonata. O canibalismo também foi registrado para os maiores indivíduos. Mudanças significativas na dieta foram relacionadas ao tamanho, com os indivíduos menores (Comprimento Total, CT <20 cm) utilizando principalmente peixes, enquanto os indivíduos maiores (CT >20 cm) se alimentaram principalmente de Odonata. A amplitude de nicho aumentou ao longo do crescimento, com indivíduos de maior porte tendo dieta mais uniformemente distribuída entre os recursos disponíveis. Nenhuma diferença significativa na composição da dieta foi encontrada entre as estações do ano, mas estômagos com maiores volumes ocupados pelo alimento foram mais frequentes no fim da primavera e menos frequentes no verão. Por outro lado, a maior amplitude de nicho foi encontrada no verão comparada com as outras estações, o que indica o uso mais uniforme dos diversos recursos disponíveis. Juntas, estas observações sugerem uma utilização eficiente dos recursos disponíveis por esta espécie predadora de topo neste novo sistema colonizado.

Effects of river damming in Neotropical piscivorous and omnivorous fish: feeding, body condition and abundances

The increase in abundance of small-sized fishes is common after a reservoir is formed. There is an increase in the consumption of fish, from typically piscivorous fish to opportunistic species that take advantage of abundant resources. This study aims to evaluate the effects of diet changes induced by damming on the feeding activity and condition factor of typically piscivorous (Hoplias aff. malabaricus and Oligosarcus longirostris ) and opportunistic (Astyanax lacustris (ex Astyanax altiparanae ) and Pimelodus britskii ). Sampling was conducted before and after the impoundment in the Iguaçu River in the region of Salto Caxias, Paraná State, Brazil. Stomach contents were analysed by the volumetric method. Feeding activity and body condition were inferred by the mean stomach repletion index and the mean condition factor. Typically piscivorous species presented a general tendency of decreased feeding activity and increased condition factor, while opportunistic species, presented a decrease in condition and feeding activity in the most affected sites. The increase in the condition factor of piscivorous fish suggests that these species benefit by the increased abundance of small size prey fish. Some opportunist species that do not have adjustments for the piscivorous diet, regardless of the intensity of consumption and resource availability, can suffer negative reflex when adopting a piscivorous diet. (AU)

O aumento na abundância de peixes de pequeno porte é comum logo após a formação de um reservatório, levando a um aumento no consumo de peixes, tanto por peixes piscívoros como oportunistas que se aproveitam do recurso abundante. Esse estudo visa avaliar os efeitos da mudança de dieta induzida pelo represamento na atividade alimentar e condição nutricional, tanto de espécies piscívoras (Hoplias aff. malabaricus e Oligosarcus longirostris ) quanto de espécies oportunistas (Astyanax lacustris (ex Astyanax altiparanae ) e Pimelodus britskii ). Para tanto, foram realizadas amostragens nas fases pré e pós-represamento no rio Iguaçu na região de Salto Caxias, Paraná, Brasil. Os conteúdos estomacais foram avaliados pelo método volumétrico. A atividade alimentar foi determinada pelo índice de repleção estomacal e a condição nutricional através do fator de condição relativo. As espécies tipicamente piscívoras apresentaram, em geral, incremento no fator de condição e queda na atividade alimentar e a espécie mais oportunista apresentou queda no fator de condição e índice de repleção nas regiões mais afetadas pelo represamento. O aumento no fator de condição de espécies piscívoras sugere que estas se beneficiam pelo aumento de abundância das espécies de pequeno porte. Enquanto espécies que não possuem adaptações para uma dieta piscívora, independente da intensidade de consumo e disponibilidade desse recurso, podem sofrer reflexos negativos em sua condição nutricional, em detrimento da ausência de pré-adaptações à piscivoria. (AU)

Effects of river damming in Neotropical piscivorous and omnivorous fish: feeding, body condition and abundances

The increase in abundance of small-sized fishes is common after a reservoir is formed. There is an increase in the consumption of fish, from typically piscivorous fish to opportunistic species that take advantage of abundant resources. This study aims to evaluate the effects of diet changes induced by damming on the feeding activity and condition factor of typically piscivorous (Hoplias aff. malabaricus and Oligosarcus longirostris ) and opportunistic (Astyanax lacustris (ex Astyanax altiparanae ) and Pimelodus britskii ). Sampling was conducted before and after the impoundment in the Iguaçu River in the region of Salto Caxias, Paraná State, Brazil. Stomach contents were analysed by the volumetric method. Feeding activity and body condition were inferred by the mean stomach repletion index and the mean condition factor. Typically piscivorous species presented a general tendency of decreased feeding activity and increased condition factor, while opportunistic species, presented a decrease in condition and feeding activity in the most affected sites. The increase in the condition factor of piscivorous fish suggests that these species benefit by the increased abundance of small size prey fish. Some opportunist species that do not have adjustments for the piscivorous diet, regardless of the intensity of consumption and resource availability, can suffer negative reflex when adopting a piscivorous diet.

O aumento na abundância de peixes de pequeno porte é comum logo após a formação de um reservatório, levando a um aumento no consumo de peixes, tanto por peixes piscívoros como oportunistas que se aproveitam do recurso abundante. Esse estudo visa avaliar os efeitos da mudança de dieta induzida pelo represamento na atividade alimentar e condição nutricional, tanto de espécies piscívoras (Hoplias aff. malabaricus e Oligosarcus longirostris ) quanto de espécies oportunistas (Astyanax lacustris (ex Astyanax altiparanae ) e Pimelodus britskii ). Para tanto, foram realizadas amostragens nas fases pré e pós-represamento no rio Iguaçu na região de Salto Caxias, Paraná, Brasil. Os conteúdos estomacais foram avaliados pelo método volumétrico. A atividade alimentar foi determinada pelo índice de repleção estomacal e a condição nutricional através do fator de condição relativo. As espécies tipicamente piscívoras apresentaram, em geral, incremento no fator de condição e queda na atividade alimentar e a espécie mais oportunista apresentou queda no fator de condição e índice de repleção nas regiões mais afetadas pelo represamento. O aumento no fator de condição de espécies piscívoras sugere que estas se beneficiam pelo aumento de abundância das espécies de pequeno porte. Enquanto espécies que não possuem adaptações para uma dieta piscívora, independente da intensidade de consumo e disponibilidade desse recurso, podem sofrer reflexos negativos em sua condição nutricional, em detrimento da ausência de pré-adaptações à piscivoria.

Uso de recursos alimentares por Plagioscion squamosissimus - piscívoro não-nativo no reservatório de Sobradinho-BA, Brasil / Use of food resources by Plagioscion squamosissimus - a non-native piscivore in Sobradinho reservoir BA-Brazil

Plagioscion squamosissimus (Heckel, 1940), popularly known as pescada, is endemic to the Amazon basin, and found in all rivers and lakes of this region. It is considered one of the main introduced species, with successful colonization in several basins in Brazil. This study aimed to evaluate the pattern of use of food resources by P. squamosissimus, in a Northeastern reservoir, with emphasis on spatial and temporal scales. Bimonthly sampling was undertaken between November 2006 and September 2009, along different stretches of the reservoir (lotic, transition and lentic) and periods (dry and flooding). A total of 44 food items were consumed, which were grouped into six categories. Diet was assessed through a combination of spatial and temporal factors using a Non-Metric Multidimensional Scaling (NMDS, PERMANOVA). The Ontogenetic change of diet was tested by means of a Multi-Response Permutation Procedure (MRPP). The results of the ordination showed that Fish was the category that mostly influenced the diet. Significant alterations were recorded during the ontogeny of P. squamosissimus. We conclude that the pescada behaves as a piscivore in the Sobradinho reservoir, thus maximizing its diet regardless of the extent of temporal and spatial variation in the reservoir.

Plagioscion squamosissimus (Heckel, 1940), conhecida popularmente como pescada, é originária da bacia Amazônica, sendo encontrada em todos os rios e lagos dessa região. É considerada uma das principais espécies introduzidas, com colonização bem sucedida em diversas bacias no Brasil. O presente trabalho teve como objetivo avaliar o padrão do uso dos recursos alimentares por P. squamosissimus, em um reservatório do Nordeste, com ênfase nas escalas espacial e temporal. Foram realizadas coletas bimestrais, entre novembro de 2006 e setembro de 2009, em diferentes trechos do reservatório de Sobradinho (lótico, transição e lêntico) e períodos (seca e cheia). Foi encontrada ampla variedade de itens alimentares, totalizando 44 itens consumidos, agrupados em seis categorias. A dieta foi avaliada através de uma combinação de fatores espaciais e temporais, utilizando a análise de Escalonamento Multidimensional Não-Métrica (NMDS, PERMANOVA). A variação ontogenética da dieta foi testada por meio de um Procedimento de Permutação Multi-resposta (PPMR). Os resultados da ordenação mostraram que Peixe foi a categoria que mais influenciou a dieta. Alterações ontogenéticas significativas também foram verificadas. Conclui-se que, no reservatório de Sobradinho, a pescada se comporta como piscívora,maximizando a dieta de acordo com a oferta e qualidade do alimento, independentemente da magnitude das variações temporais e espaciais no reservatório.

Uso de recursos alimentares por Plagioscion squamosissimus - piscívoro não-nativo no reservatório de Sobradinho-BA, Brasil / Use of food resources by Plagioscion squamosissimus - a non-native piscivore in Sobradinho reservoir BA-Brazil

Plagioscion squamosissimus (Heckel, 1940), popularly known as pescada, is endemic to the Amazon basin, and found in all rivers and lakes of this region. It is considered one of the main introduced species, with successful colonization in several basins in Brazil. This study aimed to evaluate the pattern of use of food resources by P. squamosissimus, in a Northeastern reservoir, with emphasis on spatial and temporal scales. Bimonthly sampling was undertaken between November 2006 and September 2009, along different stretches of the reservoir (lotic, transition and lentic) and periods (dry and flooding). A total of 44 food items were consumed, which were grouped into six categories. Diet was assessed through a combination of spatial and temporal factors using a Non-Metric Multidimensional Scaling (NMDS, PERMANOVA). The Ontogenetic change of diet was tested by means of a Multi-Response Permutation Procedure (MRPP). The results of the ordination showed that Fish was the category that mostly influenced the diet. Significant alterations were recorded during the ontogeny of P. squamosissimus. We conclude that the pescada behaves as a piscivore in the Sobradinho reservoir, thus maximizing its diet regardless of the extent of temporal and spatial variation in the reservoir.(AU)

Plagioscion squamosissimus (Heckel, 1940), conhecida popularmente como pescada, é originária da bacia Amazônica, sendo encontrada em todos os rios e lagos dessa região. É considerada uma das principais espécies introduzidas, com colonização bem sucedida em diversas bacias no Brasil. O presente trabalho teve como objetivo avaliar o padrão do uso dos recursos alimentares por P. squamosissimus, em um reservatório do Nordeste, com ênfase nas escalas espacial e temporal. Foram realizadas coletas bimestrais, entre novembro de 2006 e setembro de 2009, em diferentes trechos do reservatório de Sobradinho (lótico, transição e lêntico) e períodos (seca e cheia). Foi encontrada ampla variedade de itens alimentares, totalizando 44 itens consumidos, agrupados em seis categorias. A dieta foi avaliada através de uma combinação de fatores espaciais e temporais, utilizando a análise de Escalonamento Multidimensional Não-Métrica (NMDS, PERMANOVA). A variação ontogenética da dieta foi testada por meio de um Procedimento de Permutação Multi-resposta (PPMR). Os resultados da ordenação mostraram que Peixe foi a categoria que mais influenciou a dieta. Alterações ontogenéticas significativas também foram verificadas. Conclui-se que, no reservatório de Sobradinho, a pescada se comporta como piscívora,maximizando a dieta de acordo com a oferta e qualidade do alimento, independentemente da magnitude das variações temporais e espaciais no reservatório.(AU)

"Swallowing it all" - Extreme ingestion capability of juvenile reef fish / "Engolindo inteiro" - Extrema capacidade de ingestão de peixes recifais juvenis

During a predation event a juvenile grouper, rock hind Epinephelus adscensionis, fed upon the redlip blenny Ophioblennius trinitatis. It is important to highlight that both individuals had pretty much the same size during the predation event (around 5 cm); however, the grouper ingested the whole prey.

Durante um evento de predação um indivíduo juvenil de Epinephelus adscensionis (peixe-gato) alimentou-se de Ophioblennius trinitatis (macaquinho). É importante destacar que ambos os peixes apresentavam praticamente o mesmo tamanho (aproximadamente 5 cm); no entanto, a garoupa engoliu a presa inteira.

Marine diet and tobacco exposure affects mercury concentrations in pregnant women (I) from Baja California Sur, Mexico.

Seafood provides essential polyunsaturated fatty acids (PUFA) and other nutrients to pregnant women and their fetus(es) while a diet rich in finfish can be a major pathway of monomethyl mercury (MeHg+) exposure. We measured total mercury concentration ([THg]) in hair samples provided by 75 women in Baja California Sur (BCS) to assess its relationship with age, parity, tobacco smoke exposure, and diet based on survey methodologies. Generalized linear models (GLM) were used to explain the possible association of the different variables with [THg] in hair. Median [THg] in hair was 1.52 µgg-1, ranging from 0.12 to 24.19 µgg-1 and varied significantly by segment. Approximately 72% (54/75) of those evaluated exceed 1 µgg-1 [THg] and 8% (6/75) exceed 5 µgg-1 [THg] in hair. Although frequency of fish consumption contributed significantly to explaining hair [THg], fish consumption only explained 43% of [THg] in a GLM incorporating tobacco exposure and body mass index. This study establishes possible relationships among multiple potential sources of exposure and other factors related to [THg] in hair of women in the prenatal period. A more detailed examination of other sources of exposure and factors contributing to [THg] is warranted.

Relationship between self-reported fish and shellfish consumption, carbon and nitrogen stable isotope values and total mercury concentrations in pregnant women (II) from Baja California Sur, Mexico.

Seafood is a valuable source of nutrients important for fetal development. However, seafood consumption is the main route of exposure to monomethyl mercury (MeHg+) for humans. MeHg+ is highly bioavailable and potentially adversely affects fetal neurodevelopment. MeHg+ exposure from fish consumption varies significantly by age and trophic level of fish consumed as well as the frequency and amount of fish consumed. This study investigates total Hg concentrations ([THg]) in hair segments of pregnant Mexican women in relation to (1) self-reported frequency of fish and shellfish consumption, (2) maternal trophic level and marine diet contributions, determined using hair carbon (C) and nitrogen (N) stable isotopes, and (3) relates [THg] to various hair advisory thresholds. We also examined whether variation in C and N isotope values is explained by self-reported frequency of fish and shellfish consumption. A significant proportion of hair samples had [THg] higher than suggested agency thresholds and, for women within the range of the various advisory thresholds (1-20 µg g-1), the specific statistic used and threshold applied are important considerations for assessing and communicating risk. Individuals enriched in 15N (δ15N values) had higher [THg] as did individuals that reported consuming fish and shellfish more frequently, suggesting that variation in [THg] can be explained by both consumer reported diet and diet as determined by C and N stable isotope assessment. However, at higher reported fish consumption levels the trophic level is maintained while [THg] is paradoxically lower. This suggests that THg exposure and assimilation are more complicated in higher fish frequency consumption categories. [THg] is more variable at the higher concentrations, possibly indicating some exposure to non-dietary Hg, heritable variations affecting Hg toxicodynamics, and BMI and tobacco exposure factors as outlined in our companion paper.

Diet composition and food overlap of Acestrorhynchus britskii and A. lacustris (Characiformes: Acestrorhynchidae) from Sobradinho reservoir, São Francisco river, Bahia State / Composição da dieta e sobreposição alimentar de Acestrorhynchus britskii e A. lacustris (Characiformes: Acestrorhynchidae) do reservatório de Sobradinho, rio São Francisco, Estado da Bahia

Fish diet studies contribute to understanding resource partitioning and community trophic structure. The present paper characterizes the diet of "peixe-cachorro" species Acestrorhynchus britskii and A. lacustris in Sobradinho reservoir, Bahia State, Brazil. Bimonthly samples (November 2006 to July 2008) were taken in the lotic, transition and lentic stretches of the reservoir, using gillnets overnight. A total of 899 A. britskii and 476 A. lacustris stomachs were analyzed, 70% of which were empty. Their content indicated the species are predominantly piscivorous, with 18 prey fish species identified. However, each prey occurred in a single month, except for Anchoviella vaillanti, recorded in 80% of months for A. bristski, and Tetragonopterus chalceus in 25% for A. lacustris. The species presented high food overlap (Cλ = 0.992), owing to the occurrence of Actinopterygii (bits) and Actinopterygii in all months. Regarding prey fish alone, a differentiated intake and lower food overlap was detected, in the flood (Cλ = 0.427) and drought (Cλ = 0.172) seasons, in the lotic (Cλ = 0.434), transition (Cλ = 0.089) and lentic (Cλ = 0) stretches, and in overall overlap (Cλ = 0.236). The spatial and seasonal differences in the intake of different prey fish by both species suggest an opportunistic feeding habit and a competition reduction mechanism for food resources.

Estudos sobre a dieta de peixes contribuem para o entendimento da partilha de recursos e da estrutura trófica da comunidade. O presente trabalho caracteriza a dieta dos peixes-cachorro Acestrorhynchus britskii e A. lacustris no reservatório de Sobradinho, Estado da Bahia. Coletas bimestrais noturnas (Novembro/2006 a Julho/2008) foram efetuadas nos trechos lótico, transição e lêntico do reservatório, empregando redes de espera. Foram analisados 899 estômagos de A. britskii e 476 de A. lacustris, aproximadamente 70% dos quais se encontravam vazios. Seu conteúdo evidenciou tratar-se de espécies predominantemente piscívoras, com 18 peixes-presa identificados. Entretanto, cada presa ocorreu num único mês, exceto Anchoviella vaillanti, registrada em 80% dos meses para A. bristski e Tetragonopterus chalceus em 25% deles para A. lacustris. As espécies apresentaram elevada sobreposição alimentar (Cλ = 0,992), pela ocorrência de Actinopterygii (partes) e Actinopterygii não-identificado em todos os meses. Entretanto, considerando apenas os peixes-presa, foi observado consumo diferenciado e menor sobreposição alimentar, nos períodos de cheia (Cλ = 0,427) e seca (Cλ = 0,172), nos trechos lótico (Cλ = 0,434), de transição (Cλ = 0,089) e lêntico (Cλ = 0), e na sobreposição geral (Cλ = 0,236). A diferença espacial e sazonal no consumo de peixes-presa distintos pelas duas espécies sugere hábito alimentar oportunista e mecanismo de redução da competição pelos recursos alimentares.

Diet composition and food overlap of Acestrorhynchus britskii and A. lacustris (Characiformes: Acestrorhynchidae) from Sobradinho reservoir, São Francisco river, Bahia State - doi: 10.4025/actascibiolsci.v33i4.7240 / Diet composition and food overlap of Acestrorhynchus britskii and A. lacustris (Characiformes: Acestrorhynchidae) from Sobradinho reservoir, São Francisco river, Bahia State - doi: 10.4025/actascibiolsci.v33i4.7240

Fish diet studies contribute to understanding resource partitioning and community trophic structure. The present paper characterizes the diet of peixe-cachorro species Acestrorhynchus britskii and A. lacustris in Sobradinho reservoir, Bahia State, Brazil. Bimonthly samples (November 2006 to July 2008) were taken in the lotic, transition and lentic stretches of the reservoir, using gillnets overnight. A total of 899 A. britskii and 476 A. lacustris stomachs were analyzed, 70% of which were empty. Their content indicated the species are predominantly piscivorous, with 18 prey fish species identified. However, each prey occurred in a single month, except for Anchoviella vaillanti, recorded in 80% of months for A. bristski, and Tetragonopterus chalceus in 25% for A. lacustris. The species presented high food overlap (C = 0.992), owing to the occurrence of Actinopterygii (bits) and Actinopterygii in all months. Regarding prey fish alone, a differentiated intake and lower food overlap was detected, in the flood (C = 0.427) and drought (C = 0.172) seasons, in the lotic (C = 0.434), transition (C = 0.089) and lentic (C = 0) stretches, and in overall overlap (C = 0.236). The spatial and seasonal differences in the intake of different prey fish by both species suggest an opportunistic feeding habit and a competition reduction mechanism for food resources.

Fish diet studies contribute to understanding resource partitioning and community trophic structure. The present paper characterizes the diet of peixe-cachorro species Acestrorhynchus britskii and A. lacustris in Sobradinho reservoir, Bahia State, Brazil. Bimonthly samples (November 2006 to July 2008) were taken in the lotic, transition and lentic stretches of the reservoir, using gillnets overnight. A total of 899 A. britskii and 476 A. lacustris stomachs were analyzed, 70% of which were empty. Their content indicated the species are predominantly piscivorous, with 18 prey fish species identified. However, each prey occurred in a single month, except for Anchoviella vaillanti, recorded in 80% of months for A. bristski, and Tetragonopterus chalceus in 25% for A. lacustris. The species presented high food overlap (C = 0.992), owing to the occurrence of Actinopterygii (bits) and Actinopterygii in all months. Regarding prey fish alone, a differentiated intake and lower food overlap was detected, in the flood (C = 0.427) and drought (C = 0.172) seasons, in the lotic (C = 0.434), transition (C = 0.089) and lentic (C = 0) stretches, and in overall overlap (C = 0.236). The spatial and seasonal differences in the intake of different prey fish by both species suggest an opportunistic feeding habit and a competition reduction mechanism for food resources.

Diet composition and food overlap of Acestrorhynchus britskii and A. lacustris (Characiformes: Acestrorhynchidae) from Sobradinho reservoir, São Francisco river, Bahia State - doi: 10.4025/actascibiolsci.v33i4.7240 / Diet composition and food overlap of Acestrorhynchus britskii and A. lacustris (Characiformes: Acestrorhynchidae) from Sobradinho reservoir, São Francisco river, Bahia State - doi: 10.4025/actascibiolsci.v33i4.7240

Fish diet studies contribute to understanding resource partitioning and community trophic structure. The present paper characterizes the diet of peixe-cachorro species Acestrorhynchus britskii and A. lacustris in Sobradinho reservoir, Bahia State, Brazil. Bimonthly samples (November 2006 to July 2008) were taken in the lotic, transition and lentic stretches of the reservoir, using gillnets overnight. A total of 899 A. britskii and 476 A. lacustris stomachs were analyzed, 70% of which were empty. Their content indicated the species are predominantly piscivorous, with 18 prey fish species identified. However, each prey occurred in a single month, except for Anchoviella vaillanti, recorded in 80% of months for A. bristski, and Tetragonopterus chalceus in 25% for A. lacustris. The species presented high food overlap (C = 0.992), owing to the occurrence of Actinopterygii (bits) and Actinopterygii in all months. Regarding prey fish alone, a differentiated intake and lower food overlap was detected, in the flood (C = 0.427) and drought (C = 0.172) seasons, in the lotic (C = 0.434), transition (C = 0.089) and lentic (C = 0) stretches, and in overall overlap (C = 0.236). The spatial and seasonal differences in the intake of different prey fish by both species suggest an opportunistic feeding habit and a competition reduction mechanism for food resources.

Fish diet studies contribute to understanding resource partitioning and community trophic structure. The present paper characterizes the diet of peixe-cachorro species Acestrorhynchus britskii and A. lacustris in Sobradinho reservoir, Bahia State, Brazil. Bimonthly samples (November 2006 to July 2008) were taken in the lotic, transition and lentic stretches of the reservoir, using gillnets overnight. A total of 899 A. britskii and 476 A. lacustris stomachs were analyzed, 70% of which were empty. Their content indicated the species are predominantly piscivorous, with 18 prey fish species identified. However, each prey occurred in a single month, except for Anchoviella vaillanti, recorded in 80% of months for A. bristski, and Tetragonopterus chalceus in 25% for A. lacustris. The species presented high food overlap (C = 0.992), owing to the occurrence of Actinopterygii (bits) and Actinopterygii in all months. Regarding prey fish alone, a differentiated intake and lower food overlap was detected, in the flood (C = 0.427) and drought (C = 0.172) seasons, in the lotic (C = 0.434), transition (C = 0.089) and lentic (C = 0) stretches, and in overall overlap (C = 0.236). The spatial and seasonal differences in the intake of different prey fish by both species suggest an opportunistic feeding habit and a competition reduction mechanism for food resources.