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Background: Elasmobranch populations are declining, predominantly driven by overfishing, and over a third of global sharks, rays, and chimeras are estimated to be threatened with extinction. In terms of trade, Brazil is ranked the eleventh-largest shark producer and the top importer of shark meat in the world. Research has shown that elasmobranchs are sold in Brazil under the name "cação" (a generic designation for cartilaginous fish) to overcome consumer resistance., Methodology and Results: This study used DNA barcoding to investigate the sale of sharks in the State of São Paulo during the COVID-19 lockdown. A total of 35 samples of "cação" were analysed, revealing six different shark species on sale, including Carcharhinus falciformis, Carcharhinus signatus, Carcharias taurus, Isurus oxyrinchus, and Isurus paucus, that are threatened with extinction according to the IUCN red list. This study demonstrates that vulnerable elasmobranchs are being commercialised under the label "cação" in the São Paulo State and Brazil., Conclusions: Comparison of shark products traded before and during the COVID-19 pandemic showed no significant difference, suggesting lockdown did not affect patterns of species commercialisation. Effective fisheries and sale monitoring, correct product labelling legislation and increased consumer awareness that "cação" is shark are needed for appropriate conservation and management of shark populations in Brazil., (© 2023. The Author(s).)

The diets of six shark species, Sphyrna lewini, Sphyrna zygaena, Carcharhinus obscurus, Carcharhinus limbatus, Rhizoprionodon lalandii and Galeocerdo cuvier, were investigated in a subtropical coastal ecosystem of southern Brazil. Stomach content data were obtained to assess foraging niche segregation and ontogenetic shifts in the diets of these sharks. Five of the shark species off the Paraná coast were ichthyophagous, with the exception of S. zygaena, which was teutophagous. With the exception of G. cuvier, which had a generalist diet, the other five species displayed specialization in their feeding. Ontogenetic shifts were observed in C. obscurus and S. lewini with large individuals consuming elasmobranchs. Owing to the diet overlap between C. obscurus and S. lewini, C. obscurus and C. limbatus and R. lalandii and C. limbatus, future studies on the spatial and temporal distributions of these species are needed to understand the extent of competitive interactions., (© 2014 The Fisheries Society of the British Isles.)

South Brazil's archaeological coastal sites (shellmounds and middens) show a diverse collection of shark faunal remains, some of which belong to species considered rare nowadays for the region. However, shark archaeological remains identification in this region has been historically insufficient and prone to mistakes. This study identified shark fauna and estimated body size (total length) present at two archaeological sites: Rio do Meio (1220-977 Cal B.P.) and Enseada II (4286-3783 Cal B.P.), located in Santa Catarina, South of Brazil. Here, 1600 teeth and 3588 vertebrae were analysed and identified. We showed higher historical shark species richness than previously reported for South Brazil in historical and archaeological studies. In total, we identified at least 15 species of sharks (11 species and four identifications at the genus level). The presence of juvenile shark remains adds to the evidence of pre-colonial fishing impacts in local shark populations. The consistent recovery of adults and juveniles of Carcharias taurus points to a possible nursery area on the mouth of Babitonga bay. The high teeth frequency (43%) of C. taurus suggests the South Brazil coastline was once home to abundant populations of this critically endangered species. Furthermore, we discuss the presence of rare species nowadays, suggesting a possible historical residency for adult populations of Carcharodon carcharias based on the presence of juveniles and young-of-the-year on archaeological sites. The occurrence of Negaprion brevirostris, a tropical species, might have been facilitated by ocean current variations., (© 2022 Fisheries Society of the British Isles.)

Brazil currently ranks as the 11th producer and 1st importer of shark meat around the world. Data available from the FAO software FishStatJ along with data from regional sources, such as governmental bulletins, scientific papers, gray literature and internet were revisited to identify the main issues surrounding pelagic shark fisheries, trade and consumption in the largest country in South America. Among the main findings, it was noted that Brazil has not properly collected fishery statistics since 2007, that many species of threatened sharks are freely landed and traded even though it is prohibited by local legislation and/or international recommendations (regional fisheries management organizations). The blue shark ( Prionace glauca ) is the most frequently recorded shark in the official bulletins and is currently a locally targeted species. Additionally, the significant imports of this species from 23 other countries that also provide fins for Asia has drawn attention in recent decades. Regarding consumption, shark is considered to be low-value seafood compared to more common fish, such as groupers and snappers, and most Brazilians actually do not know that they are eating sharks. At present, the proportion of threatened elasmobranchs (in which sharks are included) in Brazil (33%, of 145 species) exceeds the global rate identified for the group (25%), and, until the present moment, no measure related to the management of species has been implemented. As advice, Brazil urgently needs to restructure its fishery information collection systems, management strategies and to tighten sanitary and labeling regulations for the marketing of fish. [ABSTRACT FROM AUTHOR]

Endangered sharks and rays usually often lack basic information specific to conservation, such as population size. Previous studies have reconstructed shark and ray catch statistics between 1950 and 2019 for the southeast = south of Brazil, but lacking detail at the species level, because the catches were grouped by family, genus or even common name (e.g., skates and rays, Dasyatidae, Rhinobatos, Sphyrnidae, Squatinidae). In this study, we used proportions between species from scientific observer fishing trips and Dirichlet regression modelling to reclassify these categories. This model is a multivariate extension of beta regression and enables the modeling of asymmetric and heteroscedastic compositional data, allowing multinomial data to be obtained in a more informative way. The reconstruction of catches for unclassified data showed a massive dominance of the Squatinidae family until the late 1970s, when catches showed signs of decline. At the same time, the rays of the "emplastro" family showed a progressive increase from 2006 onwards. However, this scenario changed after the reclassification. The category Squatinidae was maintained almost exclusively by S. guggenheim, while 16 categories of species were observed within "emplastro" rays, many of which fall into "endangered", "vulnerable" and "critically endangered" criteria. These reconstructed series provide a more reliable scenario of the catches of thirty elasmobranch species in the southeast and south of Brazil and serve as baseline information for understanding the conservation status of these species. [ABSTRACT FROM AUTHOR]

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Sharks are essential components of marine communities, and their removal might simplify ecosystems and lead to unpredictable and detrimental effects on the food web. Comparing the isotopic niche of species between archaeological and modern communities can provide information to assess temporal changes in the ecological dynamics of communities. Here, stable isotope analysis was used to compare food web topology metrics between two shark guilds or communities, a late Holocene archaeological community (AC) dating from 700 to 500 years ago and a modern community (MC) trophic web, both from South Brazil. In the same line of comparison, we assess the trophic position of a top predator, Carcharias taurus. Results showed topological temporal differences such as higher trophic redundancy and higher patterns of niche overlap in the AC. Higher trophic redundancy could be expected in late Holocene food webs, as similar studies also observed these findings. In contrast, the MC showed less dense packing of species within the isotopic niche space, thus higher niche partitioning and higher trophic diversity, suggesting changing ecological interaction dynamics. We found that Carcharias taurus has increased its trophic level, possibly due to a release from the intraspecific competition and a dietary shift towards larger prey items. We suggest that anthropic impacts, such as overfishing, may cause these differences in the trophic position of this species. We also advocate that this study method might help future trophic reconstructions using shark teeth, as information about past marine environments is scarce, and could serve as a baseline for future studies. [ABSTRACT FROM AUTHOR]

Copyright of Neotropical Ichthyology is the property of Neotropical Ichthyology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The tiger shark (Galeocerdo cuvier) has been relatively well assessed concerning biology and ecology aspects in both Atlantic and Pacific North America and in Caribbean waters. The amount of data in these regions has led to the species protection under capture quotas and with the creation of sanctuaries. The reality in developing countries, however, is the exact opposite, with scarce information on the species in the southern hemisphere, namely South American and African waters. In these regions, protection measures are insufficient, and studies on tiger shark biology and ecology are scarce, significantly hindering conservation and management efforts. Thus, the aim of this study was to compile scientific literature on the tiger shark in the South Atlantic and discuss the impact of these data (or lack thereof) distributed within a total of ten research categories for guiding management plans. In total, 41 scientific publications on different G. cuvier biology and ecology aspects were obtained. The most studied topics were Feeding Ecology (n = 12), followed by Human Interactions (n = 8), and Movements and Migration (n = 7). Northeastern Brazil (Southwest Atlantic) was the most researched area, probably due to the higher coastal abundance of tiger sharks in this area, alongside a high number of recorded attacks, justifying funding for studies in the region. No studies carried out in other South American or African countries were found. It is important to mention that even though some research topics are relatively well covered, a severe knowledge gap is noted for risk assessments and fisheries management, with a proposition for the implementation of sanctuaries noted. This is, however, particularly worrisome, as the South Atlantic is mostly unexplored in this regard for tiger sharks. It is also important to note how different the attention given to this species is in the North Atlantic when compared to the South region. Lastly, we highlight that the existence of sub-populations, the lack of migratory corridors geographically connecting distinct areas used by the species, and the lack of fisheries statistics on tiger shark landings, all increase the vulnerability of this species in the South Atlantic. [ABSTRACT FROM AUTHOR]

Simple Summary: The reproduction of key reef species is still largely unknown due to difficulties in documenting all elements and steps involved. Sharks are particularly affected by this scarcity of information due to being long-lived species, and witnessing courtship, gestation, and birth is still mostly limited to fortuitous encounters by divers or specimens captured by fishers. Still scarcely described in the literature, our study reports the successful reproduction of Triaenodon obesus in an ex situ environment, which offers an opportunity to observe all steps of the reproduction in detail. Furthermore, we offer the first description of the late embryonic developmental stage based on ultrasound imagery. Elasmobranchs represent a group of species under considerable anthropic pressure because of the scale of industrial and artisanal fisheries and the loss of essential areas for nursery and feeding, which are causing substantial population losses around the world. Reproduction in an ex situ environment enables a healthy population to be built and maintained in networks of public aquariums, increasing our knowledge of elasmobranch reproductive biology and offering the opportunity for reintroductions in areas where native populations have been removed. The study reports two successful pregnancies of the whitetip reef shark Triaenodon obesus, considered a vulnerable species by the International Union for the Conservation of Nature. Copulation and gestation data are provided, including ultrasound recordings of the late stage of embryo development. Ultrasonography was performed with the GE Logiq and convex transducer and revealed a fetus with defined fins and organogenesis, with definition of eyes, gills, liver, a heart with individualized chambers, partially defined kidneys, and a well-defined spiral intestine. A cartilaginous skeleton forming a posterior acoustic shadow was detailed, as well as a moving fetus with a biparietal diameter of 6.47 cm and a heart rate of 62 Beats Per Minute on spectral Doppler. This is the first successful reproduction of T. obesus in an aquarium in Brazil. [ABSTRACT FROM AUTHOR]

Simple Summary: There is a lack of detailed information on the capture pressures and records regarding the tiger shark Galeocerdo cuvier (Péron & Lesueur, 1822) (Carcharhinidae) for the state of Rio de Janeiro, Brazil. This study aimed to expand the tiger shark record database and to improve upon future conservation and management strategies in this area. A total of 23 new records were obtained, increasing the number of tiger shark records off the coast of the state of Rio de Janeiro approximately 5-fold. Possible seasonality patterns concerning tiger shark sizes were noted, indicating the need to consider the coast of Rio de Janeiro as an especially relevant area for at least part of the life history of tiger sharks. The tiger shark Galeocerdo cuvier (Péron & Lesueur, 1822) (Carcharhinidae) is classified as near-threatened along the Brazilian coast, in line with its global categorization. Although Rio de Janeiro, located in southeastern Brazil, is internationally identified as a priority shark conservation area, many shark species, including tiger sharks, are landed by both industrial and artisanal fisheries in this state. However, there is a lack of detailed information on the species capture pressures and records for the state of Rio de Janeiro. Therefore, the aims of this study were to expand the tiger shark record database and to improve upon future conservation and management strategies. Tiger shark records from four coastal Rio de Janeiro regions were obtained by direct observation. The information obtained from fishery colonies/associations, environmental guards, researchers, and scientific articles, totaling 23 records, resulted in an approximately 5-fold increase in the number of tiger shark records off the coast of the state of Rio de Janeiro. A possible seasonality pattern concerning the size of the captured/observed animals was noted, emphasizing the need to consider the coast of Rio de Janeiro as an especially relevant area for at least part of the life history of tiger sharks. [ABSTRACT FROM AUTHOR]

Ecologically or Biologically Significant Marine Areas (EBSAs) are rare, and highly important sites to the life history of a number of declining shark species are endangered by fishing.The high diversity of sharks caught by fisheries is difficult to monitor due to the scarcity of information on species‐specific biological aspects (growth, maturity and fertility rate).There are two EBSAs off north‐eastern Brazil, where key species are caught, more specifically the oceanic whitetip (Carcharhinus longimanus), mako (Isurus oxyrinchus), blue (Prionace glauca) and silky (Carcharhinus falciformis) sharks. Another 23 species displaying low frequency in catches have also been recorded, many of them considered threatened according to the IUCN Red List and the Brazilian Ministry of Environment.The main purpose of this study was to generate information about shark diversity and demonstrate the role of the two EBSAs in their conservation. After analysing fishing data collected from 2000 to 2011, maps were built to categorize shark species by phases of their ontogenetic development (neonate, young and adult) based on samples of C. falciformis (n = 330), C. longimanus (n = 440), I. oxyrinchus (n = 452) and P. glauca (n = 8,176).Shark stocks comprised mainly juveniles, which raises concerns since they are considered a crucial life stage for the sustainability of shark populations. Catch monitoring also highlighted that several of the species caught are threatened and their catch is either prohibited or limited according to the Brazilian laws and international rules in place.Action plans and enforcement of laws and rules are needed to deliver the protective measures needed for shark species in these EBSAs. [ABSTRACT FROM AUTHOR]

Elasmobranchs are apex predators that play a crucial role in marine ecosystems by regulating the dynamics of food webs, as well as connecting different trophic levels across habitats.The large‐scale removal of elasmobranchs impacts the energy transfer in trophic interactions. The pressure of unsustainable fisheries is considerable, as most elasmobranchs have reproductive strategies that render them unable to recover their demographic status after depletion.In Brazil, elasmobranchs are broadly commercialized under the generalist common name of 'cação' (namely, shark meat). This allows threatened species to be commercialized and makes the tracking of different species difficult.DNA barcoding of the Cytochrome c oxidase subunit 1 (COI) gene was applied to identify the different species sold as 'cação' along the coastline of Brazil. Fifty‐seven samples from 33 cities in 15 coastal states of Brazil were purchased and analysed.Bioinformatic analyses revealed the presence of 17 species that were sold as 'cação'. Among them, Prionace glauca (blue shark) was the most abundant. Other species, listed as Endangered under the IUCN Red List of Threatened Species, were also uncovered as being in the shark meat trade, such as Sphyrna lewini (scalloped hammerhead), Isurus paucus (longfin mako shark), and Squatina guggenheim (angular angel shark).These findings have reinforced the necessity to correctly label the commercialized species. Public actions towards species‐specific management plans must be applied, as well as monitoring the supervised allied educational programmes. [ABSTRACT FROM AUTHOR]

Large sharks generally occupy the highest trophic levels and are important links in the structuring of trophic networks. However, the decline of these predators has been observed worldwide, with population reduction rates reaching over 90% for some species. Through these declines, it is believed that the effect of the loss of predators could result in the disturbances in ecosystems. Based on this, the present study aimed to test the role of elasmobranchs in a coastal ecosystem in southern Brazil. Also, we tested if the changes in fishing effort cause changes in trophic structure. For this, a trophodynamic model was performed, based on reliable data on biomass and species feeding in the region. The mass balance modeling software Ecopath with Ecosim (EwE) was used to assess the trophic position of sharks and rays, and to understand what their interactions are with other groups in the ecosystem. Among the parameters of the model, the Paraná coast showed to be an immature system, with high connectivity and medium complexity. The trophic levels of the coast varied from 1 to 4.4, with level > 4 composed of sharks, and rays belonging to the third trophic level. Sharks were strong impacted by fishing. According to changes in fishing effort simulations, we observed changes of intermediate levels due to the decline of large sharks. However, no cascade effects were observed from the simulations. The high diversity of the system, feeding overlap, and the redundancy between mesopredator and other teleosts can decrease the chances of a cascade effect occurring. [ABSTRACT FROM AUTHOR]

The illegal sale of endangered elasmobranchs has been recorded in a number of different Brazilian states, where sharks and rays are being marketed primarily as 'cação' or 'viola'. Brazil is ranked among the top 10 nations worldwide that harvest most sharks, causing an immeasurable impact on the local elasmobranch populations.The present study applied the DNA barcoding technique, based on the cytochrome C oxidase subunit I gene, for the molecular identification of the elasmobranch species sold as processed products under the generic names of 'cação', 'mangona', 'azul', 'cambeva', 'fiuso' and 'lombo preto', in the fish market of the city of Florianópolis, capital of the state of Santa Catarina, Brazil.Nine elasmobranch species were identified in the 56 samples analysed, including six sharks and three rays, representing six families, the Carcharhinidae, Sphyrnidae, Squatinidae, Arhynchobatidae, Myliobatidae and Gymnuridae. Prionace glauca, identified in more than half (56%) of the samples analysed, is listed as Near Threatened by the International Union for the Conservation of Nature.Six species identified in the present study, Sphyrna zygaena, Sphyrna lewini, Squatina guggenheim, Carcharhinus signatus, Gymnura altavela and Rioraja agassizii, are under some level of risk of extinction, while two others (Rhizoprionodon lalandii and Myliobatis goodei) are listed as Data Deficient.Our results indicate that the commercial exploitation of endemic sharks and rays at risk of extinction is commonplace in southern Brazil. This reinforces the need for more systematic monitoring of the trade in fishery products and more effective application of the environmental legislation and conservation programmes. [ABSTRACT FROM AUTHOR]

Our study sought to analyze patterns and overlap in prey items consumed by elasmobranch species in southern Brazil through a complex network analysis. We hypothesized that species with the same habitat use would show greater trophic niche overlap and lower diet specialization than species with different habitat use. We conducted a literature survey of the species recorded in southern Brazil and analyzed publications with quantitative data on the diet of each species. We found records of 103 species in the region, of which 58 had their diets analyzed and had quantitative data to contribute to this analysis. The results suggest nested diet patterns in this community. Nestedness may arise for different reasons, and suggests that species might be balancing their high feeding niche overlap through compensatory mechanisms. There are no prior records of such a pattern in elasmobranch communities, which brings to light important information about their feeding niche. Data on prey consumption and temporal and spatial patterns of elasmobranch feeding may yield further insight into how these species are interacting in the environment and assist the investigation of the processes that shaped the current community's trophic structure. [ABSTRACT FROM AUTHOR]

Historically, Brazilian fisheries management has not considered the knowledge of fish taxonomy from within fishing communities. This study points out processes of recognition, classification and nomenclature of sharks achieved by fishermen from South Bahia, Brazil. Data were obtained through semistructured interviews visually stimulated by exhibiting images of 30 species of elasmobranch fishes. Regionally, elasmobranch species are inserted into the folk taxon called "leather fishes" and in a category known as "cação" (shark) family. In addition to hierarchical classification, the fishermen organize shark species by adopting an ethnodimorphic and sequential model based on ethnoontogeny. Ethnodiagnostic characteristics are mainly related to the morphology, ecology and even physiology of a species. A total of 144 epithets is recorded, with a mean value of 4.8 ethnospecies for each scientific correspondent. Richness of vernacular names impedes species-specific information gathering regarding shark landings if fisher knowledge is not considered and applied in the improvement of fisheries data. Thus, this study encourages the employment of fishermen as parataxonomists in order to assist in the identification of sharks to specific levels. This study further emphasizes the potential of using ethnotaxonomic knowledge of fishing communities in initiatives related to participative management of shark fisheries in developing countries. [ABSTRACT FROM AUTHOR]

The smalltail shark, Carcharhinus porosus, was the most abundant elasmobranch species in fisheries off Brazil's northern coast (BNC) in the 1980s, but its population has been declining since the 1990s. For this reason, a demographic analysis is necessary to determine the extent of this decline and the fishing effect on the BNC's population. Therefore, we performed a stochastic demographic analysis of the population in the BNC, and considered its global center of abundance. Smalltail shark specimens (n = 937) were collected with gillnets in Maranhão state, eastern BNC, in the 1980s with sizes ranging between 29.6 and 120.0 cm total length. Most of the individuals (90.6%) caught were juveniles (< 6 years-old), and the mortality and exploitation rates showed that the species was overexploited (92.3% above the fishing mortality corresponding to the population equilibrium threshold). The smalltail shark's biological characteristics, such as slow growth and low fecundity, demonstrate that it is one of the least resilient species among similar sized coastal sharks in the region. All these factors yielded an annual decrease of 28% in the intrinsic population growth rate, resulting in a population decline of more than 90% in only 10 years, and much higher for the current period. This set of features comprising fishing recruitment occurring upon juveniles, overfishing, and intrinsically low resilience make the population unable to sustain fishing pressure and severely hamper biological recruitment, thus causing this drastic population decline. Furthermore, several local extinctions for this species in the northeastern and southeastern regions of Brazil highlight its concerning conservation scenario. Therefore, since similar fisheries characteristics occur throughout its distribution range, C. porosus fits the criteria E of the IUCN Red List for a critically endangered species and urgent conservation measures are needed to prevent its extinction in the near future. [ABSTRACT FROM AUTHOR]

Sharks developed life history traits that make them susceptible to overfishing. This is, in turn, a risk for extinction, and several species are affected. The high price of shark fins in the international trade has triggered the widespread capture of sharks at unsustainable levels, prompting illegal and unethical practices, such as finning. To address these concerns, the present study aimed to identify species composition using molecular techniques based on DNA barcoding and DNA polymorphism on samples taken from illegal shark fin seizures conducted by the Federal Environmental Agency of Brazil. A species-specific DNA-based identification from three finning seizures in Brazil found at least 20 species from 747 shark fins, some of which were identified as endangered and protected under Brazilian legislation, while others were representative of restricted catches, according to Appendix II of CITES. In the seizure from Belém, 338 fins were identified as belonging to at least 19 different species, while in the seizure from Natal 211, fins belonging to at least 8 different species were identified. Furthermore, 198 fins from Cananéia were identified through PCR-Multiplex as belonging to Isurus oxyrinchus. These results raise concerns about the environmental and socioeconomic effects of finning on developing countries. Furthermore, this study represents the first finning evaluation from Brazil in the Southwest Atlantic, highlighting the importance of developing policies aimed toward restricting and regulating the shark trade and detecting IUU fisheries and illegal trade of endangered species, mainly in developing countries, where fisheries management, surveillance, and species-specific fisheries catch data are often sporatic. [ABSTRACT FROM AUTHOR]

Increasing fishing effort has caused declines in shark populations worldwide. Understanding biological and ecological characteristics of sharks is essential to effectively implement management measures, but to fully understand drivers of fishing pressure social factors must be considered through multidisciplinary and integrated approaches. The present study aimed to use fisher and trader knowledge to describe the shark catch and product supply chain in Northeastern Brazil, and evaluate perceptions regarding the regional conservation status of shark species. Non-systematic observations and structured individual interviews were conducted with experienced fishers and traders. The demand and economic value of shark fins has reportedly decreased over the last 10 years while the shark meat trade has increased slightly, including a small increase in the average price per kilogram of meat. Several threatened shark species were reportedly often captured off shore and traded at local markets. This reported and observed harvest breaches current Brazilian environmental laws. Fishing communities are aware of population declines of several shark species, but rarely take action to avoid capture of sharks. The continuing capture of sharks is mainly due to a lack of knowledge of environmental laws, lack of enforcement by responsible authorities, and difficulties encountered by fishers in finding alternative income streams. National and regional conservation measures are immediately required to reduce overfishing on shark populations in Northeastern Brazil. Social and economic improvements for poor fishing communities must also be implemented to achieve sustainable fisheries. [ABSTRACT FROM AUTHOR]

According to graph theory, the frequency distribution of trophic interactions within a food web has deep structural implications, as it can highlight the presence of patterns associated with the web and indicate whether the properties of the web are independent of its size. A hypothesis is that 'small-world' food webs are sensitive to the loss of species with the highest values. Therefore, the present work aimed to evaluate the degree to which a subtropical food web in Southern Brazil displays small-world patterns and their resistance. As part of the assessment, we evaluated the topological redundancy values of species in the food web and then we simulated the exclusion of these species (such as sharks and sea birds), and also the exclusion of high centrality species (such as squids Loligo sp., portunid swimming crabs and the cutlassfish Trichiurus lepturus). The food web showed a 'broad-scale' distribution of connections by node, and a small-world pattern. As expected, a simplification of the network was observed after elimination of some species with high centrality. However, the food web was resistant to the loss of species with low topological redundancy, probably because these species occupy a high trophic level and do not participate in lots of routes within the food web. We highlight however, the importance of the application of multiple analyses to evaluate the importance of components in food webs, and fisheries management plans should consider both species of high centrality values and species with low topological redundancy. [ABSTRACT FROM AUTHOR]

Large pelagic sharks are distributed throughout all of the oceans and are caught as bycatch in pelagic longline fisheries worldwide. In the southern Atlantic Ocean, more than a dozen shark species are caught by the Brazilian tuna longline fleet. This study compiles information of the main shark species caught by the Brazilian tuna longline fishery in the southwestern and equatorial Atlantic Ocean. Catch and effort data of 14,860 longline sets from the Brazilian chartered tuna longline fleet, between 2004 and 2010, were analyzed. The blue shark Prionace glauca was the main shark species captured by this fishery. Shark catches showed contrasting trends during the study period: the silky ( Carcharhinus falciformis) and the oceanic whitetip ( C. longimanus) sharks catch increased up to 2008 and then declined, while mako sharks ( Isurus spp.) showed an opposite trend. Effort for the Brazilian longline fishery had a higher concentration from 10°N to 30°S and from 20°W to 40°W. High values of catch per unit effort of southwestern and equatorial Atlantic Ocean sharks were heterogeneously distributed and, although elasmobranchs were caught over most of the longline fishing range, only blue sharks were caught in all areas. In the southern Atlantic Ocean, high fishing effort zones overlap significantly with some nursery areas, especially for the oceanic whitetip shark, indicating that these areas are at a direct risk from the industrial longline fishery. [ABSTRACT FROM AUTHOR]

Understanding the trophic interactions and the position of species within a foodweb is crucial if we want to understand the dynamics of marine communities and the impact individual components of the community have on trophic network compartments. Recent studies have indicated sharks and rays are important elements within foodwebs. In this study, we evaluated the ecological importance of sharks and rays in a subtropical ecosystem off the coast of southern Brazil by using topological analyses. We tested the hypotheses that some elasmobranchs can be considered key elements within the foodweb, and that large predators have topological importance (act as keystones), so that, when large predators are excluded, mesopredator elasmobranchs occupy higher topological positions. Our results indicate that Galeocerdo cuvier, Carcharhinus obscurus, Carcharias taurus, Sphyrna lewini and S. zygaena are species with large ecological function values and may exert a powerful influence over lower levels. These issues need to be considered by conservation and fishery management groups since it appears that ecosystem integrity may be compromised by reductions in the populations of large predators. Carcharhinus obscurus, S. zygaena and Zapteryx brevirostris were found to be the elasmobranchs with largest values of centrality, and can, therefore, be considered key elements in the topological structure. [ABSTRACT FROM PUBLISHER]

The present study provides a check list of elasmobranchs from the Paraná State coast, southern Brazil. Information from fish collections, literature data, field surveys and personal communications were included. Results indicated that 83 species from seven orders and 28 families were recorded. According to the results 51 species belonging to six orders and 17 families of sharks; and 32 species belonging to one order and eleven families of rays occur in this region. The most species-rich families were Carcharhinidae (14 species) and Arhynchobatidae (eight species). [ABSTRACT FROM AUTHOR]