55 resultados para Shallow Water Equations
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Injuries caused by moray eels are not a common problem, but are distributed throughout the globe, affecting mainly fishermen while manipulating hooked or netted fish. on a lesser scale, scuba divers and snorkelers, practicing or not spear fishing, are occasional victims of bites. With more than 185 species distributed among 15 genera, mostly in tropical to temperate shallow water, moray eels easily come into contact with humans and occasional injuries are not uncommon. The current study reports one case of moray eel bite and discusses the circumstances in which the accident happened, as well as wound evolution and therapy.
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The spatial and seasonal distributions of Callinectes danae Smith, 1869, in Ubatuba Bay, São Paulo, Brazil, were investigated as a part of a broad study on the general biology of portunids along the northern coast of São Paulo State, Brazil. Swimming crabs were collected during one year, from September 1995 to August 1996, along eight transects determined according to local physiographic features. Three replicate trawls were performed monthly at each transect. Depth. salinity, dissolved oxygen, temperature, organic matter content, and texture of the sediment were measured. Callinectes danae individuals were concentrated in shallow water close to the discharge of estuaries where the bottom is composed of fine and very fine sand. The species was more abundant in the warmer months. During the study period, C. danae exhibited continuous reproduction with a peak of reproductive intensity in June. Within this area, some sites are particularly favorable for C. danae establishment due to a combination of factors and prevailing local conditions.
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OBJETIVO: A biologia populacional do camarão de água doce Macrobrachium jelskii foi investigada, com ênfase na distribuição de frequência em classes de tamanho, razão sexual, período reprodutivo e recrutamento juvenil. Além disso, a abundância dos indivíduos foi correlacionada com os fatores abióticos. MÉTODOS: Amostras foram coletadas mensalmente de julho de 2005 a junho de 2007, às margens do Rio Grande, região de Planura, estado de Minas Gerais, Brasil (20º 09' S e 48º 40' W), usando uma rede de arrasto (1.0 mm tamanho da malha e 2.0 × 0.5 m de largura). O equipamento foi arrastado por duas pessoas às margens da vegetação do rio por 100 metros de distância, percorridos por uma hora. em laboratório, os espécimes foram identificados, mensurados e sexados. RESULTADOS: Um total de 2,789 espécimes foi analisado, no qual correspondem a 1,126 machos (549 jovens e 577 adultos) e 1,663 fêmeas (1,093 jovens, 423 adultos não ovígeras e 147 ovígeras). A razão sexual diferiu significativamente a favor de fêmeas de M. jelskii (1:1.48; χ² = 103.95; p < 0.0001). A média de tamanho do comprimento da carapaça (CL) das fêmeas (6.32 ± 1.84 mm CL) foi estatisticamente maior do que dos machos (5.50 ± 1.07 mm CL) (p < 0.001). A distribuição de freqüência em classes de tamanho dos espécimes revela um padrão de distribuição unimodal e não normal para machos e fêmeas (W = 0.945; p < 0.01). Não foi observada relação entre a abundância de M. jelskii e as variáveis ambientais (p = 0.799). CONCLUSÃO: A presença de fêmeas ovígeras e jovens na população sugere um padrão de reprodução e recrutamento contínuos para M. jelskii na região de Planura.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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This article describes and compares the shallow water fish-fauna from two coastal lagoons (Peixe Lagoon, in Brazil, and Mar Chiquita Lagoon, in Argentina). Peixe Lagoon was sampled between 2000 and 2001 using a 9 m beach seine net (12 mm bar mesh in the wings and 5 mm in the centre 3 m section) totalizing 125 samples, which yielded 33,848 individuals and 32 species. Mar Chiquita Lagoon was sampled from 1995 to 1998 using a 21) m beach seine net (12 mm bar mesh) totalizing 232 samples resulting in 31,097 individuals of 28 species. A total of 47 species were observed in both lagoons and 13 were shared. The "marine-estuarine-related" species were similar and dominate the fish assemblages in both lagoons. The remaining species were similar to the species collected along the southern Brazil, Uruguay and Argentina estuaries. The number of species observed in Peixe Lagoon (S = 32) was higher than in Mar Chiquita Lagoon (S = 28) and is probably associated with a strong latitudinal gradient of species richness increasing from north to south. Considering that the Peixe Lagoon and Mar Chiquita Lagoon are isolated by the large estuaries of Patos Lagoon and Prata River, the composition of the species with low abundance and occasional occurrence were different for each local studied. These results expand the knowledge for the fauna of both sites and help conservation and management from both lagoons.
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Until recently, the rhynchonelliform (articulated) brachiopod fauna from the Brazilian continental shelf (western South Atlantic) was represented only by the endemic species Bouchardia rosea (Mawe), reported from coastal waters of the states of São Paulo and Rio de Janeiro. The present study, based on samples from coastal (<30 m), shelf, and continental slope waters (99-485 m), documents the South Atlantic brachiopod fauna and shows that this fauna is more widespread, diverse, and cosmopolitan than previously thought. Based on a total of 16,177 specimens, the following brachiopods have been identified: Bouchardia rosea (Family Bouchardiidae), Platidia anomioides (Family Platidiidae), Argyrotheca cf. cuneata (Family Megathyrididae), and Terebratulina sp. (Family Cancellothyrididae). In coastal settings, the fauna is overwhelmingly dominated by Bouchardia rosea. Rare juvenile (<2 mm) specimens of Argyrotheca cf. cuneata were also found at two shallow-water sites. In shelf settings (100-200 m), the fauna is more diverse and includes Bouchardia rosea, Terebratulina sp., Argyrotheca cf. cuneata, and Platidia anomioides. Notably, Bouchardia rosea was found in waters as deep as 485 m, extending the known bathymetric range of this genus. Also, the record of this brachiopod in waters of the state of Parana is the southernmost known occurrence of this species. The genera Platidia and Terebratulina are documented here for the first time for the western South Atlantic. The Brazilian brachiopod fauna shares similarities with those from the Atlantic and Indian shelves of southern Africa, and from the Antarctic, Caribbean and Mediterranean waters. The present-day brachiopods of the western South Atlantic are much more cosmopolitan than previously thought and their Cenozoic palaeobiogeographic history has to be reconsidered from that perspective.
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Using the same methodology and identical sites, we repeat a study dating from 1973 and quantify cover of hard coral species, soft corals, sponges, hard substratum and soft substratum, and density of a commercially important reef fish species, the graysby Cephalopholis cruentata, along a depth-gradient of 3-36 m oil the coral reefs of Curacao. The objective was to determine the multi-decade change in benthic coral reef cover and structural complexity, and their effect oil densities of an associated reef fish species. Total hard coral cover decreased on average from 52% in 1973 to 22% in 2003, representing a relative decline of 58%. During this time span, the cover of hard substratum increased considerably (from 11 to 58%), as did that of soft corals (from 0.1 to 2.2%), whereas the cover of sponges showed no significant change. Relative decline of hard coral cover and of reef complexity was greatest in shallow waters (near the coast), which is indicative of a combination of anthropogenic influences from shore and recent storm damage. Cover of main reef builder coral species (Agaricia spp., Siderastrea siderea, Montastrea annularis) decreased more than that of other species, and resulted in a significant decrease in reef complexity. Although density of C. cruentata was highly correlated to cover of Montastrea and Agaricia in 1973, the loss of coral cover did not show any effect on the total density of C. cruentata in 2003. However, C. cruentata showed a clear shift in density distribution from shallow water in 1973 to deep water in 2003. It call be concluded that the reefs of Curacao have degraded considerably in the last three decades, but that this has had no major effect on the population size of one commercially important coral-associated fish species.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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The objective of this study was to characterize the fish farms located in the lowland micro region in Cuiaba, MT, through interviews with 26 selected farmers which represent the universe of fish farms that are active. Qualitative data were subjected to statistical Chi-square test to diagnose the existence of correlation between them with 95% confidence. These results support the conclusion that the species that compose the group of round fish are present in 100% of fish farms, accounting 88.2% of production. The difference is that production exclusively in nurseries and the largest area of shallow water, with production in higher scale than elsewhere in the country, with prospects of growth in area and productivity. Some actions should be implemented: legislation objectively and with sufficient qualified personnel to inspect the enterprises, applied research in food management and feed production with better price and quality, technical and administrative management, use of juveniles with proven genetics and monitoring of water quality. Fish farming is the main source of income funding for 67.5% of farmers interviewed. The size of the fish farms did not affect the variables related to implementation, conduct and management of the activity. The demand and price of feed are the variables that most directs the decision making of farmers. The main marketing channel used by medium and large farmers is exclusively, the slaughterhouses. The main part of fish is sold processed.
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In this letter we discuss the (2 + 1)-dimensional generalization of the Camassa-Holm equation. We require that this generalization be, at the same time, integrable and physically derivable under the same asymptotic analysis as the original Camassa-Holm equation. First, we find the equation in a perturbative calculation in shallow-water theory. We then demonstrate its integrability and find several particular solutions describing (2 + 1) solitary-wave like solutions. © 1999 Published by Elsevier Science B.V. All rights reserved.
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The criteria for the occurrence of roll wave phenomenon in the supercritical and turbulent Newtonian and non-Newtonian flows from the engineering point of view was analyzed. Imposing a constant discharge at the upstream of the canal and superposing a small perturbation, it was observed that roll waves can be developed more easily for small wave numbers and for high cohesions. Moreover, from the mathematical model used, it was demonstrated that the numerical viscosity was 10 times the physical viscosity.
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A site investigation program was carried out to detect salt-water intrusions in a shallow sedimentary aquifer based on electrical resistivity measurements. The site is located close to Paranaguá harbor, in the Paraná State, Brasil. At this site, high chloride concentration contaminated shallow water wells used to supply water for local industries. The site investigation program included a fieldwork, dipole-dipole electrical profiling, resistivity piezocone tests, physical-chemical analysis of sampled water and interpretation of borehole logs. The resistivity piezocone tests provided two simultaneous information; the soil stratigraphy at a very detailed level and a quasi-continuous resistivity profile. Both information adequately complemented dipole-dipole electrical profiling test data. The integration of all test data allowed identifying the contaminated areas as well as guided the location of new water wells to be installed in this area.
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Shells of Bouchardia rosea (Brachiopoda, Rhynchonelliformea) are abundant in Late Holocene death assemblages of the Ubatuba Bight, Brazil, SW Atlantic. This genus is also known from multiple localities in the Cenozoic fossil record of South America. A total of 1211 valves of B. rosea, 2086 shells of sympatric bivalve mollusks (14 nearshore localities ranging in depth from 0 to 30 m), 80 shells of Bouchardia zitteli, San Julián Formation, Paleogene, Argentina, and 135 shells of Bouchardia transplatina, Camacho Formation, Neogene, Uruguay were examined for bioerosion traces. All examined bouchardiid shells represent shallow-water, subtropical marine settings. Out of 1211 brachiopod shells of B. rosea, 1201 represent dead individuals. A total of 149 dead specimens displayed polychaete traces (Caulostrepsis). Live polychaetes were found inside Caulostrepsis borings in 10 life-collected brachiopods, indicating a syn-vivo interaction (Caulostrepsis traces in dead shells of B. rosea were always empty). The long and coiled peristomial palps, large chaetae on both sides of the 5th segment, and flanged pygidium found in the polychaetes are characteristic of the polychaete genus Polydora (Spionidae). The fact that 100% of the Caulostrepsis found in living brachiopods were still inhabited by the trace-making spionids, whereas none was found in dead hosts, implies active biotic interaction between the two living organisms rather than colonization of dead brachiopod shells. The absence of blisters, the lack of valve/site stereotypy, and the fact that tubes open only externally are all suggestive of a commensal relationship. These data document a new host group (bouchardiid rhynchonelliform brachiopods) with which spionids can interact (interestingly, spionid-infested sympatric bivalves have not been found in the study area despite extensive sampling). The syn-vivo interaction indicates that substantial bioerosion may occur when the host is alive. Thus, the presence of such bioerosion traces on fossil shells need not imply a prolonged post-mortem exposure of shells on the sea floor. Also, none of the Paleogene and Neogene Bouchardia species included any ichnological evidence for spionid infestation. This indicates that the Spionidae/ Bouchardia association may be geologically young, although the lack of older records may also reflect limited sampling and/or taphonomic biases.
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We report a case of a bather injured by a swordfish in shallow water off the coast of southern Brazil. The victim suffered multiple injuries from the fish's bill, including a puncture wound of his left knee and the tip of the bill remaining as a foreign body. The victim made a full recovery after field management and conservative care. The potential factors leading to this most unusual attack are discussed. © 2009 Wilderness Medical Society.