Variation in the isotopic composition of striped weakfish Cynoscion guatucupa of the Southwest Atlantic Ocean in response to dietary shifts / Variação na composição isotópica do Cynoscion guatucupa no Oceano Atlântico Sul

Abstract The aim of this study was to analyze the isotopic composition in muscle of striped weakfish Cynoscion guatucupa from Southwest Atlantic Ocean in order to evaluate a possible variation in δ13C and δ15N in response to dietary shifts that occur as animals grow. We also explored for isotopic evidence of differences between sample locations. The results showed an agreement between isotope analysis and previous conventional studies. Differences in the isotope composition between sampling location were not observed. A positive relation exists between isotope values and total body length of the animals. The Cluster analysis defined three groups of size classes, validated by the MDS. Differences in the relative consumption of prey species in each size class were also observed performing isotope mixing models (SIAR). Variation in δ15N among size classes would be associated with the consumption of a different type of prey as animals grow. Small striped weakfish feed on small crustaceans and progressively increase their consumption of fish (anchovy, Engraulis anchoita), increasing by this way their isotope values. On the other hand, differences in δ13C values seemed to be related to age-class specific spatial distribution patterns. Therefore, large and small striped weakfish remain specialized but feeding on different prey at different trophic levels. These results contribute to the study of the diet of striped weakfish, improve the isotopic ecology models and highlight on the importance of accounting for variation in the isotopic composition in response to dietary shifts with the size of one of the most important fishery resources in the region.

Resumo O objetivo deste estudo foi analisar a composição isotópica no músculo de Cynoscion guatucupa no Oceano Atlântico Sul Ocidental, a fim de avaliar uma possível variação de δ13C e δ15N como resposta às mudanças ontogenéticas na dieta. Foram também exploradas evidências isotópicas de diferenças entre os locais de amostragem. Os resultados mostraram uma concordância entre a análise de isótopos e os estudos convencionais prévios. Diferenças na composição isotópica entre locais de amostragem não foram observadas. Uma relação positiva existe entre valores isotópicos e comprimento total dos animais. A análise de cluster definiu três grupos de classes de tamanho, validados pelo MDS. Foram também observadas, através de modelos isotópicos mistos (SIAR), diferenças no consumo relativo de espécies de presas para cada classe de tamanho. Variações em δ15N entre as classes de tamanho estariam associadas ao consumo de diferentes tipos de presas ao longo do crescimento dos animais. Indivíduos pequenos alimentam-se de pequenos crustáceos e progressivamente aumentam seu consumo de peixes (Engraulis anchoita), aumentando assim os seus valores isotópicos. Por outro lado, as diferenças nos valores de δ13C parecem estar relacionadas com variações no padrão de distribuição espacial específico de cada classe idade. Desta maneira, tanto C. guatucupa grandes como pequenos permanecem especializados, porém alimentando-se de presas diferentes, em diferentes níveis tróficos e em diferentes áreas. Estes resultados contribuem para o estudo da dieta de C. guatucupa, melhoram os modelos de ecologia isotópica e ressaltam a importância de se considerar a variação na composição isotópica na resposta às mudanças de dieta relacionadas ao tamanho de um dos principais recursos pesqueiros da região.

Highest catch of the vulnerable broadnose sevengill shark Notorynchus cepedianus in the south-west Atlantic.

An exceptional catch of 97 broadnose sevengill sharks Notorynchus cepedianus in Samborombón Bay, Argentina, in 2013 is described from a single overnight gillnet fishing operation. Sixty-five female and 32 male N. cepedianus, ranging in size between 105-201 and 112-190 cm LT , respectively, were recorded in this catch. Fishers' observations and published information suggest that this species aggregates in the area seasonally for feeding.

Variation in the isotopic composition of striped weakfish Cynoscion guatucupa of the Southwest Atlantic Ocean in response to dietary shifts.

The aim of this study was to analyze the isotopic composition in muscle of striped weakfish Cynoscion guatucupa from Southwest Atlantic Ocean in order to evaluate a possible variation in δ13C and δ15N in response to dietary shifts that occur as animals grow. We also explored for isotopic evidence of differences between sample locations. The results showed an agreement between isotope analysis and previous conventional studies. Differences in the isotope composition between sampling location were not observed. A positive relation exists between isotope values and total body length of the animals. The Cluster analysis defined three groups of size classes, validated by the MDS. Differences in the relative consumption of prey species in each size class were also observed performing isotope mixing models (SIAR). Variation in δ15N among size classes would be associated with the consumption of a different type of prey as animals grow. Small striped weakfish feed on small crustaceans and progressively increase their consumption of fish (anchovy, Engraulis anchoita), increasing by this way their isotope values. On the other hand, differences in δ13C values seemed to be related to age-class specific spatial distribution patterns. Therefore, large and small striped weakfish remain specialized but feeding on different prey at different trophic levels. These results contribute to the study of the diet of striped weakfish, improve the isotopic ecology models and highlight on the importance of accounting for variation in the isotopic composition in response to dietary shifts with the size of one of the most important fishery resources in the region.

Variation in the isotopic composition of striped weakfish Cynoscion guatucupa of the Southwest Atlantic Ocean in response to dietary shifts

Abstract The aim of this study was to analyze the isotopic composition in muscle of striped weakfish Cynoscion guatucupa from Southwest Atlantic Ocean in order to evaluate a possible variation in 13C and 15N in response to dietary shifts that occur as animals grow. We also explored for isotopic evidence of differences between sample locations. The results showed an agreement between isotope analysis and previous conventional studies. Differences in the isotope composition between sampling location were not observed. A positive relation exists between isotope values and total body length of the animals. The Cluster analysis defined three groups of size classes, validated by the MDS. Differences in the relative consumption of prey species in each size class were also observed performing isotope mixing models (SIAR). Variation in 15N among size classes would be associated with the consumption of a different type of prey as animals grow. Small striped weakfish feed on small crustaceans and progressively increase their consumption of fish (anchovy, Engraulis anchoita), increasing by this way their isotope values. On the other hand, differences in 13C values seemed to be related to age-class specific spatial distribution patterns. Therefore, large and small striped weakfish remain specialized but feeding on different prey at different trophic levels. These results contribute to the study of the diet of striped weakfish, improve the isotopic ecology models and highlight on the importance of accounting for variation in the isotopic composition in response to dietary shifts with the size of one of the most important fishery resources in the region.

Resumo O objetivo deste estudo foi analisar a composição isotópica no músculo de Cynoscion guatucupa no Oceano Atlântico Sul Ocidental, a fim de avaliar uma possível variação de 13C e 15N como resposta às mudanças ontogenéticas na dieta. Foram também exploradas evidências isotópicas de diferenças entre os locais de amostragem. Os resultados mostraram uma concordância entre a análise de isótopos e os estudos convencionais prévios. Diferenças na composição isotópica entre locais de amostragem não foram observadas. Uma relação positiva existe entre valores isotópicos e comprimento total dos animais. A análise de cluster definiu três grupos de classes de tamanho, validados pelo MDS. Foram também observadas, através de modelos isotópicos mistos (SIAR), diferenças no consumo relativo de espécies de presas para cada classe de tamanho. Variações em 15N entre as classes de tamanho estariam associadas ao consumo de diferentes tipos de presas ao longo do crescimento dos animais. Indivíduos pequenos alimentam-se de pequenos crustáceos e progressivamente aumentam seu consumo de peixes (Engraulis anchoita), aumentando assim os seus valores isotópicos. Por outro lado, as diferenças nos valores de 13C parecem estar relacionadas com variações no padrão de distribuição espacial específico de cada classe idade. Desta maneira, tanto C. guatucupa grandes como pequenos permanecem especializados, porém alimentando-se de presas diferentes, em diferentes níveis tróficos e em diferentes áreas. Estes resultados contribuem para o estudo da dieta de C. guatucupa, melhoram os modelos de ecologia isotópica e ressaltam a importância de se considerar a variação na composição isotópica na resposta às mudanças de dieta relacionadas ao tamanho de um dos principais recursos pesqueiros da região.

Significado pronóstico de la trombosis venosa profunda asintomática en pacientes con tromboembolia de pulmón aguda sintomática / Prognostic significance of asymptomatic deep vein thrombosis in patients presenting with acute symptomatic pulmonary embolism

OBJETIVO: Evaluar el significado pronóstico de la trombosis venosa profunda (TVP) concomitante asintomática en pacientes diagnosticados de tromboembolia de pulmón (TEP) aguda sintomática. MÉTODOS: Se realizó un análisis retrospectivo de una cohorte de 820 pacientes normotensos diagnosticados de TEP aguda sintomática incluidos en el estudio PROTECT. Se les realizó una ecografía de compresión de miembros inferiores. La variable primaria de resultado fue la mortalidad por todas las causas durante los primeros 30 días de seguimiento. La variable secundaria fue la mortalidad por TEP durante el mismo período de tiempo. RESULTADOS: De los 820 pacientes incluidos, un 46% (375) presentaron TVP. El 51% de ellos (193/375) no presentaban sintomatología sugestiva de TVP. Durante el primer mes de seguimiento fallecieron 37 pacientes (4,5%; IC 95%: 3,1-5,4%). Once pacientes de 820 fallecieron por TEP (1,3%; IC 95%: 0,6-2,1%), y 26 (26 de 820 pacientes; 3,2%; IC 95%: 2,0-4,4%) por otras causas (cáncer: 10; insuficiencia cardiaca: 4; insuficiencia respiratoria: 3; sangrado: 3, y otras causas: 6). Los pacientes con TVP asintomática presentaron un riesgo aumentado de muerte por todas las causas (odds ratio [OR] 2,77; IC 95%: 1,35-5,67; p = 0,005) y de muerte por TEP (OR 7,11; IC 95%: 1,42-35,53; p = 0,02). Ninguna de las variables analizadas modificó la asociación entre la TVP asintomática y los eventos considerados. CONCLUSIONES: En pacientes normotensos con TEP aguda sintomática, la TVP asintomática concomitante se asocia a un riesgo aumentado de muerte por todas las causas y por TEP durante el mes posterior al diagnóstico

OBJECTIVE: To evaluate the prognostic significance of concomitant asymptomatic deep vein thrombosis (DVT) in patients with symptomatic acute pulmonary embolism (PE). METHODS: A prospective study was conducted on 820 normotensive patients with PE enrolled in the PROTECT multicentre study. Ultrasound was performed on patients with bilateral lower extremity venous compression to assess for concomitant DVT. The primary study outcome, all-cause mortality, and the secondary outcome of PE-specific mortality, were assessed during the first month of follow-up after PE diagnosis. RESULTS: Of the 820 patients diagnosed with PE, 46% (375/820) had concomitant DVT, and signs or symptoms of DVT were absent in 51% (193 of 375) of these patients. Overall, 37 out of 820 patients died (4,5%; 95% confidence interval [CI], 3,1%-5,9%). Of the 820 patients, 11 (1,3%; 95% CI, 0,6%-2,1%) died from PE, and 26 (3,2%; 95% CI, 2,0%-4,4%) died from other causes (cancer: 10; congestive heart failure: 4; respiratory failure: 3; major bleeding: 3; miscellaneous diseases: 6). Patients with concomitant asymptomatic DVT had an increased all-cause mortality (odds ratio [OR] 2,77; 95% CI, 1,35-5,67;P = .005) and PE-specific mortality (OR 7,11; 95% CI, 1,42-35,53; P = ,02). None of the variables analysed affected the association between DVT and the events studied. CONCLUSIONS: In stable patients with an episode of acute symptomatic PE, the presence of concomitant asymptomatic DVT is an independent predictor of death in the ensuing month after diagnosis

Fish diversity in the Río de la Plata and adjacent waters: an overview of environmental influences on its spatial and temporal structure.

The fish diversity and the main environmental factors affecting the spatial distribution of species, life history stages and community structure in the Río de la Plata (RdP) and adjacent waters are reviewed and analysed, with emphasis on the functional guild classification. The functional guild classification indicated that most species in the RdP were marine stragglers, zoobenthivores and oviparous species, although the biomass was dominated by estuarine species. Salinity had a stronger influence than temperature on the spatial pattern for all life stages, shallower and fresher waters are the preferred habitats of neonates and juveniles. During the breeding season (spring-summer), adults showed an intrusion into the inner part of RdP or to its adjacent nearshore waters from the offshore waters for spawning or mating, respectively. Variations in river discharge and wind patterns greatly affected the spatial extent of estuarine water, which ultimately influenced the domain of the main life-history stages (juveniles or adults) for both marine and estuarine fishes, as well as species and fish assemblage composition. The strong environmental gradient restricts some species and life-history stages to a particular section and defines three main fish assemblage areas. The composition of the fish assemblage is indicative of the recruitment of freshwater and marine species to the estuary in opposite ways, determined by the vertical stratification. Seasonal changes in the species composition were related to migration as a result of salinity and temperature variations and reproductive migrations to spawning and mating areas. This overview reveals that the RdP is under environmental variations that are likely to produce modifications to fish distribution and abundance that affect its fisheries. This context plus fish stock declines and changes in exploitation patterns could amplify the magnitude of the variations in the fisheries resources availability and affect the sustainability of fishing communities.

Fish and aquatic habitat conservation in South America: a continental overview with emphasis on neotropical systems.

Fish conservation in South America is a pressing issue. The biodiversity of fishes, just as with all other groups of plants and animals, is far from fully known. Continuing habitat loss may result in biodiversity losses before full species diversity is known. In this review, the main river basins of South America (Magdalena, Orinoco, Amazon and Paraná-La Plata system), together with key aquatic habitats (mangrove-fringed estuaries of the tropical humid, tropical semi-arid and subtropical regions) are analysed in terms of their characteristics and main concerns. Habitat loss was the main concern identified for all South American ecosystems. It may be caused by damming of rivers, deforestation, water pollution, mining, poor agricultural practice or inadequate management practice. Habitat loss has a direct consequence, which is a decrease in the availability of living resources, a serious social and economic issue, especially for South American nations which are all developing countries. The introduction of exotic species and overfishing were also identified as widespread across the continent and its main freshwater, coastal and marine ecosystems. Finally, suggestions are made to find ways to overcome these problems. The main suggestion is a change of paradigm and a new design for conservation actions, starting with integrated research and aiming at the co-ordinated and harmonized management of the main transboundary waters of the continent. The actions would be focused on habitat conservation and social rescue of the less well-off populations of indigenous and non-indigenous peoples. Energy and freshwater demands will also have to be rescaled in order to control habitat loss.