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Stomach contents of 175 Brazilian sharpnose sharks, Rhizoprionodon lalandii, were examined to assess their feeding habits. Caught by artisanal fishers between June 2006 and July of 2007 at Ipanema Beach, on the central coast of the state of Paraná, southern Brazil, R. lalandii appears to be piscivorous (89.7% IRI), feeding mainly on families of Clupeidae (5.1% IRI) and Sciaenidae (3.7% IRI) and secondarily on squid Lolliguncula brevis (8.6% IRI). Diets were similar between sexes and seasons. However, there were ontogenetic changes in their diets. The major items for neonates were Penaeidae crustaceans (%IRI = 56.4) and Engraulidae fishes (%IRI = 29.3); for the juveniles, Sciaenidae (%IRI = 62.5) and Clupeidae (%IRI = 19.7), and for adults Clupeidae (%IRI = 45.8) and Sciaenidae (%IRI = 15.9). Only neonate sharks consumed crustaceans, whereas all size classes consumed cephalopods and teleosts. Neonates had the lowest trophic level (TR = 3.8), with the diet of juveniles and adults the highest (TR = 4.2). Given its abundance and diet, R. lalandii may be an important predator of demersal and pelagic prey in coastal waters of Brazil. [ABSTRACT FROM AUTHOR]

The present study compares the trophic ecology of two guitarfishes (Pseudobatos percellens and Pseudobatos horkelii) from the continental shelf of the São Paulo State, Brazil, caught by the bottom pair trawls between 2007 and 2009. These two sympatric species are under different threat categories, "Vulnerable" and "Critically Endangered," respectively, according to Brazilian agencies. Thus, any study considering trophic ecology parameters is pivotal in understanding the trophic ecology role of such species in the ecosystem. The authors analysed 500 stomachs of P. percellens and 108 of P. horkelii, quantifying with dietary indexes: numerical (%N), gravimetric (%W), frequency of occurrence (%FO) and the prey-specific index of relative importance (%PSIRI). For P. percellens and P. horkelii, 26 and 14 different prey items were found, respectively. Crustacea and Teleostei were the most important prey items for both species, indicating a specialist feeding behaviour due to their low niche amplitude. The results provide evidence related to ontogenetic dietary shift in P. percellens and individual-level diet specialization in both species. These two benthic-demersal elasmobranchs are important mesopredators (3,7 for P. percellens, and 3,5 for P. horkelii) in the study area, with high trophic-level values., (© 2022 Fisheries Society of the British Isles.)

Understanding the ecological role of species with overlapping distributions is central to inform ecosystem management. Here we describe the diet, trophic level and habitat use of three sympatric stingrays, Hypanus guttatus, H. marianae and H. berthalutzae, through combined stomach content and stable isotope (δ 13 C and δ 15 N) analyses. Our integrated approach revealed that H. guttatus is a mesopredator that feeds on a diverse diet of benthic and epibenthic marine and estuarine organisms, principally bivalve molluscs, Alpheus shrimp and teleost fishes. Isotopic data supported movement of this species between marine and estuarine environments. H. berthalutzae is also a marine generalist feeder, but feeds primarily on teleost fishes and cephalopods, and consequently occupies a higher trophic level. In contrast, H. marianae is a mesopredator specialized on shrimps and polychaetas occurring only in the marine environment and occupying a low niche breadth. While niche overlap occurred, the three stingrays utilized the same prey resources at different rates and occupied distinct trophic niches, potentially limiting competition for resources and promoting coexistence. These combined data demonstrate that these three mesopredators perform different ecological roles in the ecosystems they occupy, limiting functional redundancy., (© 2022 Fisheries Society of the British Isles.)

In Amazonian streams, damming caused by road construction changes the system's hydrological dynamics and biological communities. We tested whether the degree of specialization in fish (Bryconops giacopinii) individuals is higher in pristine stream environments with intact ecological conditions than in streams dammed due to the construction of a highway in the Amazon rainforest. To achieve this, stomach content data and stable isotopes (δ 13 C and δ 15 N) in tissues with varying isotopic incorporation rates (liver, muscle, and caudal fin) were used to assess the variation in consumption of different prey over time. The indices within-individual component (WIC)/total niche width (TNW) and individual specialization were employed to compare the degree of individual specialization between pristine and dammed streams. The condition factor and stomach repletion of sampled individuals were used to infer the intensity of intraspecific competition in the investigated streams. The species B. giacopinii, typically considered a trophic generalist, has been shown to be, in fact, a heterogeneous collection of specialist and generalist individuals. Contrary to our expectations, a higher degree of individual specialization was detected in streams dammed by the highway. In dammed streams, where intraspecific competition was more intense, individuals with narrower niches exhibited poorer body conditions than those with broader niches. This suggests that individuals adopting more restricted diets may have lower fitness, indicating that individual specialization may not necessarily be beneficial for individuals. Our results support the notion that intraspecific competition is an important mechanism underlying individual specialization in natural populations. Our results suggest that environmental characteristics (e.g., resource breadth and predictability) and competition for food resources interact in complex ways to determine the degree of individual specialization in natural populations., (© 2024 Fisheries Society of the British Isles.)

Habitats with spatial variation in food availability, predation risk, and hunting pressure allow us to study how animals resolve the trade-off between food searching and predator avoidance. We investigated the influence of food availability, predation risk, and the perceived predation risk on habitat use by a primate living under high hunting pressure, the yellow-breasted capuchin monkeys, Sapajus xanthosternos, at Una Biological Reserve (ReBio Una). We hypothesized that the hunting pressure occurring in the capuchins' home range would favor predator avoidance to the detriment of searching for food. We characterized a set of covariates related to resource availability (fruit and invertebrate biomasses, feeding on dispersed and clumped food items, sleeping sites), perceived predation risk (alarm calls given to terrestrial and aerial predators, silent group movement, and vigilance behavior), and actual predation risk (evidence of hunting) and estimated their effects on how one group of capuchin monkeys uses its habitat. The group divides its time among three major forest types within their home range: agroforest, mature, and secondary. Our results suggest that the actual and perceived risk of hunting by humans, as well as the perceived predation risk by both terrestrial and aerial predators, were significant determinants of capuchin monkeys' space use. Yellow-breasted capuchin monkeys' space use was negatively related to the risk of hunting by humans (actual evidence and silent behavior), the perceived risk of predation by both aerial and terrestrial predators, and the presence of sleeping sites. Capuchin monkeys' use of space was not related to the biomass of fruits in the habitat, and the biomass of invertebrates had a very low positive effect. We confirmed our prediction that in a habitat with high hunting pressure, the risk of predation, both perceived and actual, had a more significant impact on how yellow-breasted capuchins used space than did food availability., (© 2021 Wiley Periodicals LLC.)

Copyright of Acta Zoologica Lilloana is the property of Fundacion Miguel Lillo 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.)

Although the order Rodentia does not present a high risk of extinction compared to mammals as a whole, several families demonstrate high levels of threat and/or data deficiency, therefore highlighting the need for targeted research and the application of ecological and reproductive data to the development of conservation actions. The order Rodentia, the largest among mammals, includes 9 families, and the family Cricetidae is the most diverse of the Brazilian rodents. In Brazil, 12 of the 16 genera of Oecomys are found. Oecomys bicolor is known in Brazil as the 'arboreal rat' and is, found in dry, deciduous and tropical forests. The mean body weight of Oecomys bicolor was 35.8 g and the gonadal, tubular and epithelial somatic indexes were, 0.53%, 0.47% and 0.37%, respectively. Seminiferous tubules volume density was 89.72% and the mitotic and meiotic indexes corresponded to 8.59 and 2.45 cells, respectively, and the yield of spermatogenesis was 23.83 cells. The intertubular compartment represented 10.28% of the testis parenchyma and around 5% of the interstitial space was occupied by Leydig cells, whose number per gram of testis was 11.10 × 10 7 cells. By evaluating the biometric and histomorphometric characteristics of the testis, there is evidence that this species has a high investment in reproduction. Due to the high contribution of the seminiferous epithelium and the intertubular compartment in this species, compared to the others of the same family, it is possible to infer that the species Oecomys bicolor has a promiscuous reproductive behaviour., (© 2024 Wiley‐VCH GmbH. Published by John Wiley & Sons Ltd.)

Copyright of Conhecimento & Diversidade is the property of Conhecimento & Diversidade 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.)

Although morphological abnormalities in several rays and skate species around the American continents have frequently mentioned, their numbers are unknown. The present work record morphological abnormalities in four Urotrygonidae species. Two anophthalmic specimens were detected (Urotrygon microphthalmum and Urobatis halleri). Two individuals lacked caudal fins (Urobatis maculatus and Urotrygon chilensis). Two round rays showed incomplete fusion of the pectoral fin to the head (U. microphthalmum and U. chilensis). Vertebral compression and fusion were found in a 6‐year‐old female Urotrygon rogersi. In addition, 118 abnormal batomorph specimens were gathered from the available bibliography, spanning the last six decades (1959–2021). Amblyraja doellojuradoi was the species with the highest number of abnormalities (18). The most common anomaly was an incomplete fusion of the pectoral fin with the head. Since 2010, at least 30 anomalous batomorphs have been recorded every 5 years. Sixty‐nine abnormal specimens occurred in the Northern Hemisphere (1.00–60.00 N). The Cortezian (Pacific) and Southeastern Brazil (Atlantic) marine ecoregions stood out with the highest number of these specimens. Mexico recorded 58 anomalous specimens, followed by Brazil (n = 36). Biological, abiotic and anthropogenic factors are probably the leading causes. However, additional studies are necessary to elucidate these speculations. [ABSTRACT FROM AUTHOR]

The knowledge of the population structure of a given species is of great importance for its conservation and for the management of its fishing exploitation, especially for sharks. The tiger shark (Galeocerdo cuvier Péron&Lesueur, 1822) is an apex predator species that is currently listed as "Near Threatened" on the International Union for the Conservation of Nature's (IUCN) Red List of Threatened Species. In this study, the tiger shark's genetic structure in the Metropolitan Region of Recife (MRR) and oceanic archipelago of Fernando de Noronha (FN) was investigated based on one mitochondrial and two nuclear DNA markers. In addition, sequenced data from other geographic sites were added into the mitochondrial analysis. The data showed moderate‐to‐high genetic diversity, and it is consistent with good resilience of G. cuvier in ecological terms. The structuring tests reinforced a global distinction of the species in two lineages, one being from the Indo‐Pacific and the other from the North Atlantic. Also, this analysis showed the close relationship between tiger sharks from Indo‐Pacific and South‐eastern coast of Brazil. The Bayesian and AMOVA tests indicated that tiger sharks from FN and MRR are genetically similar, forming a cohesive population. These analyses support live specimen translocations from beaches (where the attacks occur) to distant marine areas given we detected a historical cohesive population occurring between those beaches from MRR and FN Islands where the sharks migrate. This research is the first that has validated individual translocations as a green strategy in South‐western Atlantic. [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]

Coastal and offshore ecotypes of common bottlenose dolphins have been recognized in the western South Atlantic, and it is possible that trophic niche divergence associated with social interactions is leading them to genetic and phenotypic differentiation. The significant morphological differentiation observed between these ecotypes suggests they represent two different subspecies. However, there is still a need to investigate whether there is congruence between morphological and genetic data to rule out the possibility of ecophenotypic variation accompanied by gene flow. Mitochondrial DNA (mtDNA) control region sequence data and 10 microsatellite loci collected from stranded and biopsied dolphins sampled in coastal and offshore waters of Brazil as well as 106 skulls for morphological analyses were used to determine whether the morphological differentiation was supported by genetic differentiation. There was congruence among the data sets, reinforcing the presence of two distinct ecotypes. The divergence may be relatively recent, however, given the moderate values of mtDNA nucleotide divergence (dA = 0.008), presence of one shared mtDNA haplotype and possibly low levels of gene flow (around 1% of migrants per generation). Results suggest the ecotypes may be in the process of speciation and reinforce they are best described as two different subspecies until the degree of nuclear genetic divergence is thoroughly evaluated: Tursiops truncatus gephyreus (coastal ecotype) and T. t. truncatus (offshore ecotype). The endemic distribution of T. t. gephyreus in the western South Atlantic and number of anthropogenic threats in the area reinforces the importance of protecting this ecotype and its habitat. [ABSTRACT FROM AUTHOR]

Sympatric species are expected to differ in ecological requirements to minimize niche overlap and avoid competition. Here we assess the trophic interactions among three coexisting dolphin species from southern Brazil: the franciscana dolphin (Pontoporia blainvillei), the Guiana dolphin (Sotalia guianensis), and the Lahille's bottlenose dolphin (Tursiops truncatus gephyreus). We evaluated temporal variation in carbon (δ13C) and nitrogen (δ15N) isotope values of bone collagen to examine potential dietary shifts resulting from increased fishing activity over the past three decades. We estimated the degree of niche overlap among these species and the contribution of potential prey sources to their diet. δ15N values were consistent among species and across years, while δ13C values increased for Guiana dolphins and decreased for bottlenose dolphins, suggesting changes in diet and/or foraging habitats through time. The similar δ13C and δ15N values and the high niche overlap between Guiana and bottlenose dolphins indicate that these species are primarily feeding on demersal prey. The franciscana diet is primarily composed of pelagic prey, resulting in a lower niche overlap in comparison with the other dolphin species. Our study provides further information about the foraging ecology of this unique dolphin community in southern Brazil with implications for its management and conservation. [ABSTRACT FROM AUTHOR]

Biogeographic regionalization identifies natural species assemblages of a given region. In this study, the geographic distribution of chondrichthyan species richness and species assemblages for the Southwest Atlantic were identified. The geographic distribution of 103 chondrichthyans was estimated through modelling. Based on the obtained binary maps, the distribution of chondrichthyan richness was obtained at four taxonomic levels: class Chondrichthyes (chondrichthyans), subclass Holocephali (chimaeras), division Selachii (sharks), and division Batomorphi (batoids). The continental shelf off Uruguay and southern Brazil presented the highest levels of chondrichthyan richness, and a smaller peak was found in El Rincón (northern Argentina). Shark richness concentrated mainly off Lagoa dos Patos (southern Brazil). Batoid richness was maximal off Uruguay and northern Argentina, including modes in El Rincón, San Jorge Gulf, and slope of the Argentinean shelf. Classification analyses revealed the presence of a hierarchical regionalization, with three main and six minor assemblages. Main assemblages are hierarchically identifiable as provinces and minor ones as ecoregions or districts. Two of the main assemblages correspond with the Argentinean and Magellanic Provinces; the third one is identified here for the first time, the Patagonian Slope Province. This regionalization provides the basis for the design of protected area networks for conservation or management purposes. [ABSTRACT FROM AUTHOR]

The loss of canopy‐forming seaweeds from urbanized coasts has intensified in response to warming seas and non‐climatic pressures such as population growth and declining water quality. Surprisingly, there has been little information on the extent of historical losses in the South‐western Atlantic, which limits our ability to place this large marine ecosystem in a global context. Here, we use meta‐analysis to examine long‐term (1969–2017) changes to the cover and biomass of Sargassum spp. and structurally simple algal turfs along more than 1,000 kilometres of Brazil's warm temperate coastline. Analysis revealed major declines in canopy cover that were independent of season (i.e., displaying similar trends for both summer and winter) but varied with coastal environmental setting, whereby sheltered bays experienced greater losses than coastal locations. On average, covers of Sargassum spp. declined by 2.6% per year, to show overall losses of 52% since records began (ranging from 20% to 89%). This contrasted with increases in the cover of filamentous turfs (24% over the last 27 years) which are known to proliferate along human‐impacted coasts. To test the relative influence of climatic versus non‐climatic factors as drivers of this apparent canopy‐to‐turf shift, we examined how well regional warming trends (decadal changes to sea surface temperature) and local proxies of coastal urbanization (population density, thermal pollution, turbidity and nutrient inputs) were able to predict the changes in seaweed communities. Our results revealed that the most pronounced canopy losses over the past 50 years were at sites exhibiting the greatest degree of coastal warming, the highest population growth and those located in semi‐enclosed sheltered bays. These findings contribute knowledge on the drivers of canopy loss in the South‐western Atlantic and join with global efforts to understand and mitigate declines of marine keystone species. [ABSTRACT FROM AUTHOR]

Data on stranded sea turtles were examined between 2010 and 2016 along the northern region of Rio de Janeiro state and between 2016 and 2017 in the southern region, looking for spatio‐temporal patterns and determining which factors contributed to their mortality.A total of 12,162 strandings of all five species that occur in Brazil were recorded, with Chelonia mydas being the most common (89.9%). Sea turtles use the Rio de Janeiro coast as a feeding and/or migration area. The intense upwelling (October to April) may be an important factor for the sea turtles feeding in this region, mainly for Eretmochelys imbricata and Dermochelys coriacea, which had a higher number of strandings during this period.Areas further north of the study area include an important nesting site for Caretta caretta in Brazil, which explains the higher concentration of strandings of subadults/adults of this species in this region and during its nesting season.Many anthropogenic threats to sea turtles were documented, mainly incidental capture in fisheries and marine debris, indicating possible hotspots for these threats in the regions of Sepetiba and Guanabara Bays, Cabo Frio, and São Francisco de Itabapoana.Among the natural causes of strandings, the primary factors were chronic illness, endoparasites, and fibropapillomatosis. However, pollution may also be an indirect threat, which negatively affects these animals through reduced health and immunosuppression, leaving them more susceptible to opportunistic diseases.These data are valuable for directing and implementing specific and local mitigation measures along the Rio de Janeiro state coast, such as avoiding bycatch hotspots through fleet communication programmes and/or area and seasonal closures, enforceable legislation, effective penalties and proper waste management. [ABSTRACT FROM AUTHOR]

During 1442 h of visual observations over 7 years throughout the World Heritage listed Paranaguá estuarine complex, Brazil, seven occurrences of interactions were observed at a single location involving breaching Manta birostris displacing schools of teleosts, which were subsequently preyed upon by Sotalia guianensis. Although the interactions were not definitively categorized as being amensal, commensal or mutual, their restriction to isolated space (adjacent to a protected area) and time (summer) supports previous assertions the area is important to regional productivity and the continuation of protected-area status. [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]

The spotback skate Atlantoraja castelnaui (Arhynchobatidae) is a large and threatened skate species subjected to fishing pressure, endemic to the Southwest Atlantic that occurs from Rio de Janeiro, Brazil, to San Jorge Gulf, Argentina. The age, growth, age at maturity and the maximum intrinsic rate of population increase r max of A. castelnaui were studied using 152 specimens collected from off Uruguay and north Argentina (35°-42° S), between June 2013 and February 2020. Vertebrae from 143 individuals were used for ageing (females: n = 83, size range 404-1300 mm total length, TL; males: n = 60, size range 400-1270 mm TL). Maximum ages determined for females and males were 30 and 28 years, respectively. To fit growth models, non-linear and Bayesian estimation approaches were considered. For the first approach, a set of four candidate growth (size-at-age) models were fitted: three-parameter von Bertalanffy, two-parameter von Bertalanffy with fixed L 0 , Gompertz and Logistic. In the second approach, von Bertalanffy, Gompertz and Logistic were fitted. For non-linear estimation, model selection indicated that the entire set of candidate growth models were supported by the data. The von Bertalanffy was selected as the best model for Bayesian estimation. There were no differences in growth between sexes. For the sexes combined, the von Bertalanffy growth model by Bayesian method was considered the most adequate to describe the growth of A. castelnaui (growth mean parameters ± S.D.: L ∞  = 1210.29 ± 40.68 mm; k = 0.12 ± 0.01 years -1 ; L 0  = 179.20 ± 11.62 mm). The age at maturity was estimated at 16.21 and 14.04 years for females and males, respectively. The maximum intrinsic rate of population increase r max was estimated as 0.252 years -1 . Life-history traits and r max provided in the present study suggest that this species has a relatively low productivity and may be vulnerable to an intense fishing pressure., (© 2021 Fisheries Society of the British Isles.)

The franciscana (Pontoporia blainvillei) is a small cetacean endemic to the South Atlantic distributed in coastal waters from Espírito Santo State in Brazil to Chubut Province in Argentina. Babitonga Bay, on the northern coast of Santa Catarina State, Brazil, is home to the only known franciscana population that resides throughout the year in an estuary. Photo-identification is a technique that serves to identify individuals in their natural environment through photographs of natural or artificial body marks. The objective of this paper was to assess the feasibility of identifying individuals from this population from marks present on the dorsal fin and the body. From February 2011 to August 2013, 172 boat surveys were carried out in Babitonga Bay. Groups of franciscanas were recorded on 576 occasions and on 542 of these (94.09%) were photographed. A total of 6,953 (11.89%) from a total of 58,471 photographs were considered of high enough quality to distinguish the features used to identify individuals. Throughout the sampling period, 23 franciscanas were identified. Most of the animals exhibited nicks on the trailing edge of the dorsal fin (82.6%), a mark of longterm duration. Scratches were recorded on only one animal on a single occasion. The rate of resightings ranged from 5.26% to 78.95%, with 39.13% of the individuals showing a rate higher than 50%. A total of 41.8% of the Babitonga Bay population was identified by the presence of marks on the dorsal fin. The study indicates that photo-identification can be applied to franciscanas, which may allow the realisation of various future studies. Because of this species threatened status, the use of this technique may become particularly important for monitoring franciscanas in Babitonga Bay and perhaps in other regions. [ABSTRACT FROM AUTHOR]

The article focuses on an attack by smooth hammerhead sharks on some pantropical spotted dolphins in waters off Brazil, and discusses some features of group antipredation tactics. A linear regression model was used to examine the relationship between distances from adult dolphins followed by sharks to subgroups.

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 purpose of the present study was to analyze the diet of the smooth butterfly ray Gymnura micrura using qualitative and quantitative approaches to describe the feeding spectrum as well as ecological aspects related to feeding and niche width. The rays were obtained through monthly sampling as by-catch from bottom trawl fisheries in northeastern Brazil from August 2007 to July 2008. A total of 286 stomachs were sampled, of which 176 contained food items. G. micrura is a predator in the region that feeds intermittently on large whole prey items, followed by a long period of digestion with simply little or no feeding activity. A low diversity of food items was found in the G. micrura diet, with an absolute predominance of teleosts, especially the roughneck grunt Pomadasys corvinaeformis. It is suggested that the species has a narrow feeding niche and a high degree of specialization. This presumed high degree of feeding specialization is discussed and the findings are compared in light of similar studies for closely related species, allowing to propose the family as primarily constituting piscivorous rays. [ABSTRACT FROM AUTHOR]

Two tagged-and-recaptured tiger sharks Galeocerdo cuvier, measuring 172 and 304 cm total length ( LT) and at age 0·75 and 3·50 years, exhibited unmatched growth rates of 118·4 and 55·5 cm year−1, respectively. The larger fish was nearly mature, indicating that G. cuvier off Brazil could mature considerably earlier than conspecifics from other regions. [ABSTRACT FROM AUTHOR]

The article presents a research study regarding the non-standard fishing of large sharks in Paraná, Brazil. Research shows the shark species that are being fished in the state including Elasmobranch, Trichiuridae, Rhinopteridae, and rays and 60 specimens have already recorded. Furthermore, dusky sharks are commonly caught by Brazilian fishermen in the coastal area of the state.

The distribution limits in the Atlantic of Callorhinchus callorynchus (Callorhinchidae) and Odontesthes argentinensis (Atherinopsidae) are extended northwards to 22° 22′ S and 22° 31′ S, respectively, whereas that of Lile piquitinga (Clupeidae) is extended southwards to 22° 22′ S. Their occurrence in the north of Rio de Janeiro State is discussed. Remarks on the osteology of O. argentinensis, and morphometric and meristic data of L. piquitinga, are also provided. [ABSTRACT FROM AUTHOR]

This study presents the second worldwide report on abnormal embryos of the sharpnose sharks, Rhizoprionodon, based on the two species (Rhizoprionodon porosus and Rhizoprionodon lalandii) occurring on the Brazilian coast. For R. porosus two conjoined twin embryos showing complete duplication of the vertebral column, viscera and several external structures (head, first and second dorsal fins, pectoral fins), and scoliosis in both axis at the pelvic fin level are reported. The three embryos of R. lalandii exhibited numerous lordosis and kyphosis along the entire vertebral column. The possible relationship between anomalies and the human major threats to sharks is discussed based on previous reproductive, genetic and ecotoxicological studies on R. lalandii for southern Brazil. [ABSTRACT FROM PUBLISHER]