266 research outputs found
Comparison of deterministic growth models fitted to length-at-age data of the piked spurdog (Squalus megalops) in south-eastern Australia
No full text© CSIRO 2007Age and growth estimates of Squalus megalops were derived from the first dorsal fin spine of 452 sharks, ranging from 274 to 622mm total length. Age bias plots and indices of precision indicated that the ageing method was precise and unbiased. Edge analysis of the enameled surface of whole spines and similarities in the banding pattern deposited in the enameled surface of spines and in spine sections supported the hypothesis of annual band formation. Multiple versions of two growth models were fitted to length-at-age data, from which a two-phase von Bertalanffy model produced the best fit. For males, the change in growth rate corresponded with size-at-maturity, whereas for females, the change was slightly before size-at-maturity. Regardless of the growth model used, growth rate of females (0.034 to 0.098 years−1) was very low, making S. megalops highly susceptible to overexploitation by fisheries.J. Matías Braccini, Bronwyn M. Gillanders, Terence I. Walker and Javier Tovar-Avil
Contradicción, coherencia y compromiso: Matías Usero Torrente
No full textThe current article studies the figure of Matías Usero Torrente. His thought is considered by the author as a preceding of the principals ideas that emphasized about the relations between State and Society during the sixties in Spain.En el presente artículo se analiza la figura de Matías Usero Torrente. Su pensamiento es considerado por la autora del estudio como antecesor de las principales ideas que sobre las relaciones de la Iglesia con el Estado y la Sociedad cristalizaron en la década de los 60 en España
Sources of variation in the feeding ecology of the piked spurdog (Squalus megalops): implications for inferring predator - prey interactions from overall dietary composition
No full textAbstract
Sources of variation in dietary composition were examined in the piked spurdog (Squalus megalops). The species is an opportunistic predator that consumes a wide range of prey items. When importance of prey was measured by weight or occurrence, S. megalops preyed largely on molluscs and teleosts. However, when number of prey was considered, the main items were crustaceans. A bootstrap analysis showed that considerable variability can be expected in the importance of prey items in the species' overall diet. Regional, seasonal, and ontogenetic differences in dietary composition were found, but there were no differences between mature and immature sharks or between males and females. The spatial and temporal variation in diet exhibited by S. megalops and the intrinsic natural variability of the dietary composition of this opportunistic predator suggest that studies that infer predator–prey interactions from overall diet are likely to miss information on the ecological relationships among species and thus account for only part of these interactions.J. Matías Braccini, Bronwyn M. Gillanders, and Terence I. Walke
Hierarchical approach to the assessment of fishing effects on non-target chondrichthyans: case study of Squalus megalops in southeastern Australia
No full textA three-levelled hierarchical risk assessment approach was trialed using piked spurdog (Squalus megalops) to evaluate the suitability of the approach for chondrichthyan species. At level 1, a qualitative assessment indicated that the only fishing-related activity to have moderate or high impact on S. megalops was "capture fishing" by otter trawl, Danish seine, gillnet, and automatic longline methods. At level 2, a semi-quantitative assessment ranked S. megalops at risk because of its low biological productivity and, possibly, its catch susceptibility from cumulative effects across the separate fishing methods. Finally, at level 3, a quantitative assessment showed that population growth is slow even under the assumption of density-dependent compensation where the fishing mortality rate equals the natural mortality rate. Although published information indicates that relative abundance has been stable in several regions of southern Australia, it is concluded that given its low biological productivity, changed fishing practices leading to increased fishing mortality could quickly put S. megalops at high risk. The hierarchical approach appears particularly useful for assessment of chondrichthyan species in data-limited fisheries. This approach allows for a management response at any level, optimizing research and management efforts by identifying and excluding low-risk species from data intensive assessments.J. Matías Braccini, Bronwyn M. Gillanders, and Terence I. Walke
Determining reproductive parameters for population assessments of chondrichthyan species with asynchronous ovulation and parturition: piked spurdog (Squalus megalops) as a case study
No full textPopulation assessments of chondrichthyan species require several key parameters of their reproductive biology, which were estimated for Squalus megalops (Macleay, 1881). Length-at-maturity differed depending on the criterion adopted for defining maturity. In the case of males, length-at-maturity was smallest when condition of seminal vesicles was adopted as a maturity criterion. For females, length-at-maturity was smallest when the largest follicle diameter >3 mm was adopted as the criterion for maturity; this was appropriate only as an indicator of the onset of maturity. Mature males are capable of mating throughout the year. Females have a continuous asynchronous reproductive cycle. The sex ratio of embryos is 1 : 1 and litter size and near-term embryo length increase with maternal length. Females have an ovarian cycle and gestation period of two years. This was reflected in the differences found between the maturity and maternity ogives. Although all females are mature at 600 mm, only 50% of them contribute to annual recruitment each year. Hence, for chondrichthyan species with reproductive cycles of two, three or more years, if maturity ogives are used in population assessments instead of maternity ogives, the models will overestimate recruitment rates.J. Matías Braccini, Bronwyn M. Gillanders A and Terence I. Walke
La filial de Matías Celedón: escritura de oficina
No full textThis article, fundamentally, investigates the possible links that may be established between material conditions and scriptural procedures of La filial by Matías Celedón and the concept of «Death of the Author»(1968) by Roland Barthes. It also reviews the bureaucratic and oppressive structure and atmosphere of the office in which the plot takes place, proposing a comparison with two classic works on the subject: Bartleby the Scrivener (1853) and Bouvard and Pécuchet (1880). Finally, it is alludes to references of experimental poetry such as Martín Gubbins, Guillermo Deisler, Elsa Werth y Sergio Chejfec, among others, with the aim of outlining a kind of «Office Writing» that transcends the usual differences between the narrative and poetic genres.Este artículo indaga, fundamentalmente, en los posibles vínculos que puedan establecerse entre las condiciones materiales y procedimientos escriturales de La filial de Matías Celedón y el concepto «muerte del autor» (1968) de Roland Barthes. También revisa la estructura y la atmósfera burocrática y agobiante de la oficina en la que se desarrolla la trama, planteando una comparación con dos obras clásicas sobre el tema: Bartleby el escribiente (1853) y Bouvard y Pécuchet (1880). Finalmente, alude a referentes de la poesía experimental como Martín Gubbins, Guillermo Deisler, Elsa Werth y Sergio Chejfec, entre otros, con el objetivo de perfilar una suerte de «escritura de oficina» que trasciende las diferencias habituales entre los géneros narrativo y poético
El MOJO ya es periodismo: Entrevista a Matías Amigo
No full textThis interview shows the benefits of mobile technology as an instrument to promote journalistic work. Matías Amigo is an Argentinian audiovisual producer, author of the guide Iniciación al periodismo móvil, and the first Latin American journalist to give a lecture at the MojoFest in Ireland, the world"™s most important event on
Mobile Journalism (MOJO). The dialogue also explores the benefits of mobile journalism and the reasons why media and journalists may feel reluctant or fearful at the idea of using these tools to report news.Esta entrevista muestra los beneficios de la tecnología móvil como un instrumento para facilitar el trabajo periodístico. Matías Amigo es un realizador audiovisual argentino, autor de la guía Iniciación al periodismo móvil, y el primer latino en dictar una conferencia en el MojoFest de Irlanda, el evento más importante del mundo sobre Mobile Journalism (MOJO). Asimismo, el diálogo explora las ventajas del periodismo móvil y las razones por las que los medios y periodistas se pueden sentir reacios o temerosos ante la idea de emplear estas herramientas para reportear noticias
Assessing growth band counts from vertebrae and dorsal-fin spines for ageing sharks: comparison of four methods applied to Heterodontus portusjacksoni
No full textFour methods for counting growth bands using vertebrae and dorsal-fin spines of the Port Jackson shark, Heterodontus portusjacksoni, are compared. Both calcified structures presented observable growth bands, allowing cross comparison among structures for the first time in a shark species. Whole and sectioned vertebrae and dorsal fin-spines possess highly visible growth bands and intra-reader band counts resulted in similar precision indices with little systematic bias. However, inter-reader growth band count plots showed possible biases in counts from sectioned vertebrae and sectioned dorsal-fin spines. Sectioned vertebrae and whole and sectioned dorsal-fin spines produced similar growth band counts, whereas whole vertebrae produced significantly lower counts. The similar readability, precision indices, growth band counts and apparent absence of biases between counts for a single reader would indicate that sectioned vertebrae and whole and sectioned dorsal-fin spines are both potentially useful and acceptable methods for band counting. However, inter-reader comparisons are necessary to avoid acceptance of biased estimations, resulting in over- or under-estimations of age. Validation for all age classes is essential to determining accurate age estimations for this and other species.Javier Tovar-Ávila, Christopher Izzo, Terence I. Walker, J. Matías Braccini and Robert W. Da
Nota bibliográfica sobre los libros impresos en Bilbao por Matías Mares
No full textMatías Mares fue un impresor en Bilbao en el siglo XVI. Parece ser que se estableció en Bilbao en 1577 ó 1578 donde estuvo hasta 1587. Se da la bibliografía de los libros que imprimió durante su estancia en Bilbao. Se describen estos libros y se notifica los lugares en los que se encuentran algunos de los ejemplaresMatías Seas was a printer in Bilbao in the 16th century. It seems that he settled in Bilbao in 1577 or 1578, where he stayed until 1587. The author provides the bibliography of the books that he printed during his stay in Bilbao. The author also describes these books and informs on where some of the copies can be found toda
Linking spatial stock dynamics and economics: Evaluation of indicators and fishery management for the travelling eastern king prawn (Melicertus plebejus)
No full textReduced economic circumstances havemoved management goals towards higher profit, rather than maximum sustainable yields in several Australian fisheries. The eastern king prawn is one such fishery, for which we have developed new methodology for stock dynamics, calculation of model-based and data-based reference points and management strategy evaluation. The fishery is notable for the northward movement of prawns in eastern Australian waters, from the State jurisdiction of New South Wales to that of Queensland, as they grow to spawning size, so that vessels fishing in the northern deeper waters harvest more large prawns. Bioeconomic fishing data were standardized for calibrating a length-structured spatial operating model. Model simulations identified that reduced boat numbers and fishing effort could improve profitability while retaining viable fishing in each jurisdiction. Simulations also identified catch rate levels that were effective for monitoring in simple within-year effort-control rules. However, favourable performance of catch rate indicators was achieved only when a meaningful upper limit was placed on total allowed fishing effort. Themethods and findings will allow improved measures for monitoring fisheries and inform decision makers on the uncertainty and assumptions affecting economic indicators
- …
