Influence of season, environment and feeding habits on the enzymatic activity of peptidase and -glucosidase in the gastrointestinal tract of two Siluriformes fishes (Teleostei)

The enzymatic activities involved in the digestion of proteins and carbohydrates were compared among three organs of the digestive track of two Siluriformes fish species, and between two areas: a reservoir, and an area downriver of it. Our aim was to test the hypothesis that the digestive organs of species with varied feeding habits have different enzymatic activities, and that the enzymatic activity differs among seasons and environmental conditions. The iliophagous/herbivorous species Hypostomus auroguttatus Kner, 1854 had higher trypsin-like, chymotrypsin-like peptidase and -glucosidase activity in the intestine when compared with the omnivorous species Pimelodus maculatus Lacepède, 1803, whereas the latter had more hepatic trypsin-like activity than the former. The peak of activity of the three enzymes in H. auroguttatus was recorded in the winter and spring. On the other hand, P. maculatus tended to have the more prominent peptidase and -glucosidase activity in the summer, and the smallest in the winter. The intestine of H. auroguttatus had higher enzymatic (trypsin, chymotrypsin and -glucosidase) activity than the stomach and the liver. For P. maculatus, the highest -glucosidase activity was found in the liver. The enzymatic activity of H. aurogutattus did not differ between lotic and lentic systems, whereas P. maculatus had comparatively higher stomach and hepatic trypsin levels and hepatic chymotrypsin-like activities in the reservoir than down in the river. These findings indicate that, in H. auroguttatus, most digestive activity occurs in the intestine, which is long and adapted for the digestion of bottom-river vegetable matter and detritus. The seasons and the type of the system (lentic vs. lotic) seem to affect the enzymatic activity for these two species differently, a likely consequence of their different lifestyles.

Influence of season, environment and feeding habits on the enzymatic activity of peptidase and -glucosidase in the gastrointestinal tract of two Siluriformes fishes (Teleostei)

The enzymatic activities involved in the digestion of proteins and carbohydrates were compared among three organs of the digestive track of two Siluriformes fish species, and between two areas: a reservoir, and an area downriver of it. Our aim was to test the hypothesis that the digestive organs of species with varied feeding habits have different enzymatic activities, and that the enzymatic activity differs among seasons and environmental conditions. The iliophagous/herbivorous species Hypostomus auroguttatus Kner, 1854 had higher trypsin-like, chymotrypsin-like peptidase and -glucosidase activity in the intestine when compared with the omnivorous species Pimelodus maculatus Lacepède, 1803, whereas the latter had more hepatic trypsin-like activity than the former. The peak of activity of the three enzymes in H. auroguttatus was recorded in the winter and spring. On the other hand, P. maculatus tended to have the more prominent peptidase and -glucosidase activity in the summer, and the smallest in the winter. The intestine of H. auroguttatus had higher enzymatic (trypsin, chymotrypsin and -glucosidase) activity than the stomach and the liver. For P. maculatus, the highest -glucosidase activity was found in the liver. The enzymatic activity of H. aurogutattus did not differ between lotic and lentic systems, whereas P. maculatus had comparatively higher stomach and hepatic trypsin levels and hepatic chymotrypsin-like activities in the reservoir than down in the river. These findings indicate that, in H. auroguttatus, most digestive activity occurs in the intestine, which is long and adapted for the digestion of bottom-river vegetable matter and detritus. The seasons and the type of the system (lentic vs. lotic) seem to affect the enzymatic activity for these two species differently, a likely consequence of their different lifestyles.

Influence of season, environment and feeding habits on the enzymatic activity of peptidase and -glucosidase in the gastrointestinal tract of two Siluriformes fishes (Teleostei)

The enzymatic activities involved in the digestion of proteins and carbohydrates were compared among three organs of the digestive track of two Siluriformes fish species, and between two areas: a reservoir, and an area downriver of it. Our aim was to test the hypothesis that the digestive organs of species with varied feeding habits have different enzymatic activities, and that the enzymatic activity differs among seasons and environmental conditions. The iliophagous/herbivorous species Hypostomus auroguttatus Kner, 1854 had higher trypsin-like, chymotrypsin-like peptidase and -glucosidase activity in the intestine when compared with the omnivorous species Pimelodus maculatus Lacepède, 1803, whereas the latter had more hepatic trypsin-like activity than the former. The peak of activity of the three enzymes in H. auroguttatus was recorded in the winter and spring. On the other hand, P. maculatus tended to have the more prominent peptidase and -glucosidase activity in the summer, and the smallest in the winter. The intestine of H. auroguttatus had higher enzymatic (trypsin, chymotrypsin and -glucosidase) activity than the stomach and the liver. For P. maculatus, the highest -glucosidase activity was found in the liver. The enzymatic activity of H. aurogutattus did not differ between lotic and lentic systems, whereas P. maculatus had comparatively higher stomach and hepatic trypsin levels and hepatic chymotrypsin-like activities in the reservoir than down in the river. These findings indicate that, in H. auroguttatus, most digestive activity occurs in the intestine, which is long and adapted for the digestion of bottom-river vegetable matter and detritus. The seasons and the type of the system (lentic vs. lotic) seem to affect the enzymatic activity for these two species differently, a likely consequence of their different lifestyles.

Reproductive plasticity of Hypostomus affinis (Siluriformes: Loricariidae) as a mechanism to adapt to a reservoir with poor habitat complexity

In this work we describe the gonad morphology and spawning season of Hypostomus affinis (Steindachner, 1877) in a tropical reservoir based on 55 males and 125 females. Our aim was to assess eventual adaptations in reproductive tactics developed by this riverine species inhabiting an oligotrophic reservoir with low habitat complexity, few rocks and few other preferred consolidated substrata. We described the stages of cells of reproductive lineage, gonadal development and some reproductive traits which were compared with information in the available literature. Cells from the spermatogenic lineage were spermatogonia, spermatocytes, spermatids and spermatozoa, and cells from the oocytarian lineage were primary oocytes, previtelogenic oocytes, cortical vesicle oocytes and yolk globules or vitellogenic. Five stages were described for the males/females according to the distribution of oocytes and spermatogenic lineage cells: resting; initial maturation; advanced maturation; partially spent/spawned; totally spent/spawn. Females outnumbered males and reached larger size. Synchronic ovary development in two groups was found with diameter of mature oocytes ranging from 2 to 3.35 mm. Indication of early maturation, a longer reproductive period and the production of smaller eggs in small clutches seems to be features of the reservoir population not found in riverine systems. Such changes in tactics may indicate a shift to an opportunistic strategy, helping the population to withstand environmental constraints and to succeed in this oligotrophic and poorly structured reservoir.

Reproductive plasticity of Hypostomus affinis (Siluriformes: Loricariidae) as a mechanism to adapt to a reservoir with poor habitat complexity

In this work we describe the gonad morphology and spawning season of Hypostomus affinis (Steindachner, 1877) in a tropical reservoir based on 55 males and 125 females. Our aim was to assess eventual adaptations in reproductive tactics developed by this riverine species inhabiting an oligotrophic reservoir with low habitat complexity, few rocks and few other preferred consolidated substrata. We described the stages of cells of reproductive lineage, gonadal development and some reproductive traits which were compared with information in the available literature. Cells from the spermatogenic lineage were spermatogonia, spermatocytes, spermatids and spermatozoa, and cells from the oocytarian lineage were primary oocytes, previtelogenic oocytes, cortical vesicle oocytes and yolk globules or vitellogenic. Five stages were described for the males/females according to the distribution of oocytes and spermatogenic lineage cells: resting; initial maturation; advanced maturation; partially spent/spawned; totally spent/spawn. Females outnumbered males and reached larger size. Synchronic ovary development in two groups was found with diameter of mature oocytes ranging from 2 to 3.35 mm. Indication of early maturation, a longer reproductive period and the production of smaller eggs in small clutches seems to be features of the reservoir population not found in riverine systems. Such changes in tactics may indicate a shift to an opportunistic strategy, helping the population to withstand environmental constraints and to succeed in this oligotrophic and poorly structured reservoir.

Reproductive plasticity of Hypostomus affinis (Siluriformes: Loricariidae) as a mechanism to adapt to a reservoir with poor habitat complexity

In this work we describe the gonad morphology and spawning season of Hypostomus affinis (Steindachner, 1877) in a tropical reservoir based on 55 males and 125 females. Our aim was to assess eventual adaptations in reproductive tactics developed by this riverine species inhabiting an oligotrophic reservoir with low habitat complexity, few rocks and few other preferred consolidated substrata. We described the stages of cells of reproductive lineage, gonadal development and some reproductive traits which were compared with information in the available literature. Cells from the spermatogenic lineage were spermatogonia, spermatocytes, spermatids and spermatozoa, and cells from the oocytarian lineage were primary oocytes, previtelogenic oocytes, cortical vesicle oocytes and yolk globules or vitellogenic. Five stages were described for the males/females according to the distribution of oocytes and spermatogenic lineage cells: resting; initial maturation; advanced maturation; partially spent/spawned; totally spent/spawn. Females outnumbered males and reached larger size. Synchronic ovary development in two groups was found with diameter of mature oocytes ranging from 2 to 3.35 mm. Indication of early maturation, a longer reproductive period and the production of smaller eggs in small clutches seems to be features of the reservoir population not found in riverine systems. Such changes in tactics may indicate a shift to an opportunistic strategy, helping the population to withstand environmental constraints and to succeed in this oligotrophic and poorly structured reservoir.

Influence of the river flow on the structure of fish assemblage along the longitudinal gradient from river to reservoir

Changes in fish assemblage structure along a longitudinal gradient of the Paraíba do Sul River and Funil reservoir were studied to detect distribution patterns and the seasonal influence of the inflowing river. Fish were caught by gill nets in three zones (riverine, transition and lentic) during two seasons (dry and wet). A total of 3,721 individuals were captured, comprising five orders, 14 families, 27 genera and 33 species. Five species were non-native and amounted to 17.7% of the total number of individuals. The 10 most abundant species were used to assess spatial-temporal patterns. Plagioscion squamosissimus (Heckel, 1840), Oligosarcus hepsetus (Curvier, 1829) and Metynnis maculatus (Kner, 1858) were widely distributed in both seasons. Astyanax bimaculatus (Linnaeus, 1758), Cichla kelberi Kullander & Ferreira, 2006 and Geophagus brasiliensis (Quoy & Gaimard, 1824) had higher abundance in the dry season, occurring mainly in the lentic zone. By contrast, the benthopelagics Pimelodus maculatus La Cèpede, 1803 and Astyanax parahybae (Eigenmann, 1908) and the benthics Hoplosternum littorale (Hancock, 1828) and Hypostomus auroguttatus Kner, 1854 had higher abundance in the wet season, with the two first species occurring mainly in the riverine zone, and latter two species in the transition zone. The highest diversity for both seasons was recorded in the transition zone, which is an ecotone that allows the co-existence of both riverine and lentic species. A major shift in assemblage structure occurred along the longitudinal gradient due to changes in discharge of the inflowing river, with increased fish abundance in the riverine zone caused by increased habitat availability in wet season, and the reverse of this situation in the dry season.

Influence of the river flow on the structure of fish assemblage along the longitudinal gradient from river to reservoir

Changes in fish assemblage structure along a longitudinal gradient of the Paraíba do Sul River and Funil reservoir were studied to detect distribution patterns and the seasonal influence of the inflowing river. Fish were caught by gill nets in three zones (riverine, transition and lentic) during two seasons (dry and wet). A total of 3,721 individuals were captured, comprising five orders, 14 families, 27 genera and 33 species. Five species were non-native and amounted to 17.7% of the total number of individuals. The 10 most abundant species were used to assess spatial-temporal patterns. Plagioscion squamosissimus (Heckel, 1840), Oligosarcus hepsetus (Curvier, 1829) and Metynnis maculatus (Kner, 1858) were widely distributed in both seasons. Astyanax bimaculatus (Linnaeus, 1758), Cichla kelberi Kullander & Ferreira, 2006 and Geophagus brasiliensis (Quoy & Gaimard, 1824) had higher abundance in the dry season, occurring mainly in the lentic zone. By contrast, the benthopelagics Pimelodus maculatus La Cèpede, 1803 and Astyanax parahybae (Eigenmann, 1908) and the benthics Hoplosternum littorale (Hancock, 1828) and Hypostomus auroguttatus Kner, 1854 had higher abundance in the wet season, with the two first species occurring mainly in the riverine zone, and latter two species in the transition zone. The highest diversity for both seasons was recorded in the transition zone, which is an ecotone that allows the co-existence of both riverine and lentic species. A major shift in assemblage structure occurred along the longitudinal gradient due to changes in discharge of the inflowing river, with increased fish abundance in the riverine zone caused by increased habitat availability in wet season, and the reverse of this situation in the dry season.

Influence of the river flow on the structure of fish assemblage along the longitudinal gradient from river to reservoir

Changes in fish assemblage structure along a longitudinal gradient of the Paraíba do Sul River and Funil reservoir were studied to detect distribution patterns and the seasonal influence of the inflowing river. Fish were caught by gill nets in three zones (riverine, transition and lentic) during two seasons (dry and wet). A total of 3,721 individuals were captured, comprising five orders, 14 families, 27 genera and 33 species. Five species were non-native and amounted to 17.7% of the total number of individuals. The 10 most abundant species were used to assess spatial-temporal patterns. Plagioscion squamosissimus (Heckel, 1840), Oligosarcus hepsetus (Curvier, 1829) and Metynnis maculatus (Kner, 1858) were widely distributed in both seasons. Astyanax bimaculatus (Linnaeus, 1758), Cichla kelberi Kullander & Ferreira, 2006 and Geophagus brasiliensis (Quoy & Gaimard, 1824) had higher abundance in the dry season, occurring mainly in the lentic zone. By contrast, the benthopelagics Pimelodus maculatus La Cèpede, 1803 and Astyanax parahybae (Eigenmann, 1908) and the benthics Hoplosternum littorale (Hancock, 1828) and Hypostomus auroguttatus Kner, 1854 had higher abundance in the wet season, with the two first species occurring mainly in the riverine zone, and latter two species in the transition zone. The highest diversity for both seasons was recorded in the transition zone, which is an ecotone that allows the co-existence of both riverine and lentic species. A major shift in assemblage structure occurred along the longitudinal gradient due to changes in discharge of the inflowing river, with increased fish abundance in the riverine zone caused by increased habitat availability in wet season, and the reverse of this situation in the dry season.

Dieta de juvenis de Trachinotus carolinus (Actinopterygii, Carangidae) em praias arenosas na costa do Rio de Janeiro

We studied the diet of juvenile Trachinotus carolinus (Linnaeus, 1766) in sandy beaches of Sepetiba Bay (Rio de Janeiro, Brazil), between January 2000 and April 2001. We tried to evaluate the trophic plasticity of fish this species along a spatial gradient of wave exposure, seasonality, besides to evaluate ontogenetic changes in the diet. The Index of Relative Importance (IRI) was used to measure the food items, determined by their frequency of occurrence, numbers and weights. The subphylum Crustacea, mainly the order Mysidacea, Decapoda Emerita brasiliensis (Schmitt, 1935) and Cephalochordata, represented by Branchiostoma platae (Fitzinger, 1862) were dominant in the diet. In the most exposed zone (Barra de Guaratiba beach) with predominant sandy substrate, the diet was comprised mainly by Emerita brasiliensis and Cirripedia, this later item common in rocky shores at the beach edge; in the intermediate exposed beach (Muriqui beach), Mysidacea and Branchiostoma platae; in the most protected beach (Itacuruçá beach), Polychaeta, Mysidacea and Branchiostoma platae was predominant. No seasonal change was recorded for the use of Mysidacea, while Branchiostoma platae was the more consumed during the winter, Polychaeta in spring, Cirripedia and Emerita brasiliensis, in summer. Mysidacea was the predominate food in all size classes, while Polychaeta was used predominantly by fish smaller than 20 mm standard length (SL) and Emerita brasiliensis and Cirripedia, were consumed mainly by larger individuals than 40 mm in the most exposed beach only. The success in use of surf zones and sand beaches by this fishes species, it can be partly, due the opportunist trophic strategy that uses a wide variety of available resources on environmental.

Estudamos a dieta dos juvenis de Trachinotus carolinus (Linnaeus, 1766) em praias da Baía de Sepetiba (Rio de Janeiro, Brasil) entre janeiro de 2000 e abril de 2001. Procuramos avaliar a plasticidade trófica de peixes desta espécie ao longo de um gradiente espacial com diferentes níveis de exposição às ondas, sazonalidade, além de avaliar mudanças ontogenéticas na dieta. Os itens alimentares foram analisados através do índice de importância relativa (IIR), determinado pelos valores das frequências de ocorrência, de número e de peso. Os itens de maior importância foram do subfilo Crustacea, ordens Mysidacea, e o representante da ordem Decapoda Emerita brasiliensis (Schmitt, 1935), além de Cefalochordata, representado por Branchiostoma platae (Fitzinger, 1862). Na zona de maior exposição às ondas (praia de Barra de Guaratiba) e com substrato predominantemente arenoso, a dieta foi constituída principalmente por Emerita brasiliensis e Cirripedia, este último presente nos costões rochosos que limitam a praia; na zona de exposição intermediária (praia de Muriqui), houve um predomínio de Mysidacea e Branchiostoma platae; na zona mais protegida (praia de Itacuruçá), os itens de maior abundância foram Polychaeta, Mysidacea e Branchiostoma platae. Sazonalmente não ocorreu variação no uso de Mysidacea, enquanto Branchiostoma platae foi mais consumido durante o inverno, Polychaeta na primavera e Cirripedia e Emerita brasiliensis, no verão. Mysidacea foi o alimento predominante em todas as classes de tamanho, enquanto Polychaeta foi utilizado predominantemente por peixes menores que 20 mm de comprimento padrão e Emerita brasiliensis e Cirripedia foram consumidos principalmente por indivíduos maiores que 40 mm, somente na praia de maior exposição. O sucesso no uso de praias desprotegidas e zonas de arrebentação por esta espécie de peixe pode ser em parte devido à estratégia trófica oportunista, que utiliza uma ampla variedade de recursos disponíveis no ambiente.

Dieta de juvenis de Trachinotus carolinus (Actinopterygii, Carangidae) em praias arenosas na costa do Rio de Janeiro

We studied the diet of juvenile Trachinotus carolinus (Linnaeus, 1766) in sandy beaches of Sepetiba Bay (Rio de Janeiro, Brazil), between January 2000 and April 2001. We tried to evaluate the trophic plasticity of fish this species along a spatial gradient of wave exposure, seasonality, besides to evaluate ontogenetic changes in the diet. The Index of Relative Importance (IRI) was used to measure the food items, determined by their frequency of occurrence, numbers and weights. The subphylum Crustacea, mainly the order Mysidacea, Decapoda Emerita brasiliensis (Schmitt, 1935) and Cephalochordata, represented by Branchiostoma platae (Fitzinger, 1862) were dominant in the diet. In the most exposed zone (Barra de Guaratiba beach) with predominant sandy substrate, the diet was comprised mainly by Emerita brasiliensis and Cirripedia, this later item common in rocky shores at the beach edge; in the intermediate exposed beach (Muriqui beach), Mysidacea and Branchiostoma platae; in the most protected beach (Itacuruçá beach), Polychaeta, Mysidacea and Branchiostoma platae was predominant. No seasonal change was recorded for the use of Mysidacea, while Branchiostoma platae was the more consumed during the winter, Polychaeta in spring, Cirripedia and Emerita brasiliensis, in summer. Mysidacea was the predominate food in all size classes, while Polychaeta was used predominantly by fish smaller than 20 mm standard length (SL) and Emerita brasiliensis and Cirripedia, were consumed mainly by larger individuals than 40 mm in the most exposed beach only. The success in use of surf zones and sand beaches by this fishes species, it can be partly, due the opportunist trophic strategy that uses a wide variety of available resources on environmental.

Estudamos a dieta dos juvenis de Trachinotus carolinus (Linnaeus, 1766) em praias da Baía de Sepetiba (Rio de Janeiro, Brasil) entre janeiro de 2000 e abril de 2001. Procuramos avaliar a plasticidade trófica de peixes desta espécie ao longo de um gradiente espacial com diferentes níveis de exposição às ondas, sazonalidade, além de avaliar mudanças ontogenéticas na dieta. Os itens alimentares foram analisados através do índice de importância relativa (IIR), determinado pelos valores das frequências de ocorrência, de número e de peso. Os itens de maior importância foram do subfilo Crustacea, ordens Mysidacea, e o representante da ordem Decapoda Emerita brasiliensis (Schmitt, 1935), além de Cefalochordata, representado por Branchiostoma platae (Fitzinger, 1862). Na zona de maior exposição às ondas (praia de Barra de Guaratiba) e com substrato predominantemente arenoso, a dieta foi constituída principalmente por Emerita brasiliensis e Cirripedia, este último presente nos costões rochosos que limitam a praia; na zona de exposição intermediária (praia de Muriqui), houve um predomínio de Mysidacea e Branchiostoma platae; na zona mais protegida (praia de Itacuruçá), os itens de maior abundância foram Polychaeta, Mysidacea e Branchiostoma platae. Sazonalmente não ocorreu variação no uso de Mysidacea, enquanto Branchiostoma platae foi mais consumido durante o inverno, Polychaeta na primavera e Cirripedia e Emerita brasiliensis, no verão. Mysidacea foi o alimento predominante em todas as classes de tamanho, enquanto Polychaeta foi utilizado predominantemente por peixes menores que 20 mm de comprimento padrão e Emerita brasiliensis e Cirripedia foram consumidos principalmente por indivíduos maiores que 40 mm, somente na praia de maior exposição. O sucesso no uso de praias desprotegidas e zonas de arrebentação por esta espécie de peixe pode ser em parte devido à estratégia trófica oportunista, que utiliza uma ampla variedade de recursos disponíveis no ambiente.

Effects of the proximity from an industrial plant on fish assemblages in the rio Paraíba do Sul, southeastern Brazil

This work aims to analyze changes in the fish assemblages along a longitudinal reaches of the rio Paraíba do Sul, one of the most used Brazilian aquatic systems, to assess the river "health" and to identify eventual recovery trends. Standardized monthly samplings were carried out at six sites, from October 1997 to September 1999, using casting, sieves, seine and gill nets. Three zones were searched: upstream (Z I), downstream (Z III) and nearby the source of pollution (Z II). Three univariate distribution methods were used: ABC (abundance-biomass curves), K-dominance curves, and geometric class's distribution. Additionally, cluster analysis was applied to detect eventual patterns. The ABC and K-dominance curves showed Z II with evident indication of stress in both yearly cycles, followed by Z III and Z I. Few rare species and absence of common species in Z I, presence of common and abundant species, mainly opportunist, in Z II, and the highest number of rare species in Z III, was the overall pattern showed by geometric class. Number of fish was higher at Z II, while number of species did no change significantly among zones. Cluster analysis separate Z II samples from Z I and III. All the three univariate methods showed evident signals of stress at Z II, which showed indication of organic enrichment as expressed in the high abundance of common species, although physicochemical variables (ammonia, nitrogen, total phosphorous and DBO) have increased slightly from Z1 to Z III. A lesser stress condition was shown at the downstream zone (Z III), indicating the river recovery capacity. The use of biological indicators in this study proved to be a better tool to assess non-point sources pollution when compared to traditional physicochemical measurements.

Objetiva-se no presente trabalho, analisar mudanças nas assembléias de peixes ao longo de um trecho longitudinal do rio Paraíba do Sul, um dos sistemas aquáticos mais usados do Brasil, para avaliar a "saúde" do rio e identificar eventuais tendências de recuperação. Amostragens mensais foram realizadas em seis locais, de outubro de 1997 a setembro de 1999, utilizando redes de espera, tarrafas, peneiras e picaré. Foram atribuídas três zonas para avaliar as assembléias de peixes: Z II (complexo industrial da cidade de Volta Redonda - fonte da poluição), Z I (montante do complexo industrial) e Z III (jusante do complexo industrial). Três métodos univariados foram usados: ABC (curvas de abundância-biomassa), curvas de K-dominância, e distribuição por classes geométricas. Adicionalmente, foram aplicadas análises de agrupamento para verificar padrões de distribuição das espécies. A curva ABC e a curva de K-dominância indicaram maior estresse para a Z II, em ambos os ciclos anuais seguido pelas Z III e I. A classe geométrica apresentou um padrão de poucas espécies raras e ausência de espécies comuns para a Z I, presença de espécies comuns e abundância de espécies oportunistas para a Z II, e maior número de espécies raras na Z III. O número de indivíduos foi maior na Zona II, enquanto o número de espécies não teve variação significativa entre as zonas. A análise de agrupamento separou as amostras da Z II das Z I e III. Todos os três métodos utilizados no presente trabalho apresentaram maior número de espécies comuns para a Z II, indicando maior estresse para Z II, zona que recebe maior carga de efluentes de origem orgânica e industrial. Uma melhor condição foi apresentada para o trecho mais a jusante (Z III), indicando a capacidade de recuperação do rio. O uso de indicadores biológicos neste estudo provou ser uma melhor ferramenta para avaliar poluição difusa quando comparada com métodos físico-químicos tradicionais.

Effects of the proximity from an industrial plant on fish assemblages in the rio Paraíba do Sul, southeastern Brazil

This work aims to analyze changes in the fish assemblages along a longitudinal reaches of the rio Paraíba do Sul, one of the most used Brazilian aquatic systems, to assess the river "health" and to identify eventual recovery trends. Standardized monthly samplings were carried out at six sites, from October 1997 to September 1999, using casting, sieves, seine and gill nets. Three zones were searched: upstream (Z I), downstream (Z III) and nearby the source of pollution (Z II). Three univariate distribution methods were used: ABC (abundance-biomass curves), K-dominance curves, and geometric class's distribution. Additionally, cluster analysis was applied to detect eventual patterns. The ABC and K-dominance curves showed Z II with evident indication of stress in both yearly cycles, followed by Z III and Z I. Few rare species and absence of common species in Z I, presence of common and abundant species, mainly opportunist, in Z II, and the highest number of rare species in Z III, was the overall pattern showed by geometric class. Number of fish was higher at Z II, while number of species did no change significantly among zones. Cluster analysis separate Z II samples from Z I and III. All the three univariate methods showed evident signals of stress at Z II, which showed indication of organic enrichment as expressed in the high abundance of common species, although physicochemical variables (ammonia, nitrogen, total phosphorous and DBO) have increased slightly from Z1 to Z III. A lesser stress condition was shown at the downstream zone (Z III), indicating the river recovery capacity. The use of biological indicators in this study proved to be a better tool to assess non-point sources pollution when compared to traditional physicochemical measurements.

Objetiva-se no presente trabalho, analisar mudanças nas assembléias de peixes ao longo de um trecho longitudinal do rio Paraíba do Sul, um dos sistemas aquáticos mais usados do Brasil, para avaliar a "saúde" do rio e identificar eventuais tendências de recuperação. Amostragens mensais foram realizadas em seis locais, de outubro de 1997 a setembro de 1999, utilizando redes de espera, tarrafas, peneiras e picaré. Foram atribuídas três zonas para avaliar as assembléias de peixes: Z II (complexo industrial da cidade de Volta Redonda - fonte da poluição), Z I (montante do complexo industrial) e Z III (jusante do complexo industrial). Três métodos univariados foram usados: ABC (curvas de abundância-biomassa), curvas de K-dominância, e distribuição por classes geométricas. Adicionalmente, foram aplicadas análises de agrupamento para verificar padrões de distribuição das espécies. A curva ABC e a curva de K-dominância indicaram maior estresse para a Z II, em ambos os ciclos anuais seguido pelas Z III e I. A classe geométrica apresentou um padrão de poucas espécies raras e ausência de espécies comuns para a Z I, presença de espécies comuns e abundância de espécies oportunistas para a Z II, e maior número de espécies raras na Z III. O número de indivíduos foi maior na Zona II, enquanto o número de espécies não teve variação significativa entre as zonas. A análise de agrupamento separou as amostras da Z II das Z I e III. Todos os três métodos utilizados no presente trabalho apresentaram maior número de espécies comuns para a Z II, indicando maior estresse para Z II, zona que recebe maior carga de efluentes de origem orgânica e industrial. Uma melhor condição foi apresentada para o trecho mais a jusante (Z III), indicando a capacidade de recuperação do rio. O uso de indicadores biológicos neste estudo provou ser uma melhor ferramenta para avaliar poluição difusa quando comparada com métodos físico-químicos tradicionais.

Water level influences on body condition of Geophagus brasiliensis (Perciformes: Cichlidae) in a Brazilian oligotrophic reservoir

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.

Water level influences on body condition of Geophagus brasiliensis (Perciformes: Cichlidae) in a Brazilian oligotrophic reservoir

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.

Estomatite Vesicular Alagoas (VSA) em tilápia nilótica ( Oreochromis niloticus). Possível implicação epidemiológica

Foram realizadas inoculações experimentais do vírus da Estomatite Vesicular Alagoas (VSA) em tilápia nilótica(Oreochromis niloticus), pela via intraperitoneal e por imersão em suspensão viral, com o objetivo de verificar" se omesmo se replicava neste sistema hospedeiro e se o vírus era eliminado na água, o que poderia representar umimportante papel no ciclo epidemiológico da virose. Os peixes foram dispostos em grupos testemunhos e inoculadoscom suspensão de vírus VSA, tanto pela via intraperitoneal quanto por imersão. Foram observadas alteraçõesanatomopatológicas em órgãos da cavidade abdominal e cérebro. Esses órgãos e a água do aquário foram inoculadosem células BHK21 e observados a presença de efeito citopático característico dos vírus pertencentes a este gênero. Asegunda passagem do vírus em peixes confirmou as lesões encontradas anteriormente e o isolamento em novasinoculações em cultivo celular. Os resultados sugerem que a tilápia é sensível ao VSA nas duas vias de inoculação,elimina formas infectantes do· vírus na água, podendo representar um importante elo na cadeia epidemiológica daestomatite vesicular.

Estomatite Vesicular Alagoas (VSA) em tilápia nilótica ( Oreochromis niloticus). Possível implicação epidemiológica

Foram realizadas inoculações experimentais do vírus da Estomatite Vesicular Alagoas (VSA) em tilápia nilótica(Oreochromis niloticus), pela via intraperitoneal e por imersão em suspensão viral, com o objetivo de verificar" se omesmo se replicava neste sistema hospedeiro e se o vírus era eliminado na água, o que poderia representar umimportante papel no ciclo epidemiológico da virose. Os peixes foram dispostos em grupos testemunhos e inoculadoscom suspensão de vírus VSA, tanto pela via intraperitoneal quanto por imersão. Foram observadas alteraçõesanatomopatológicas em órgãos da cavidade abdominal e cérebro. Esses órgãos e a água do aquário foram inoculadosem células BHK21 e observados a presença de efeito citopático característico dos vírus pertencentes a este gênero. Asegunda passagem do vírus em peixes confirmou as lesões encontradas anteriormente e o isolamento em novasinoculações em cultivo celular. Os resultados sugerem que a tilápia é sensível ao VSA nas duas vias de inoculação,elimina formas infectantes do· vírus na água, podendo representar um importante elo na cadeia epidemiológica daestomatite vesicular.