ALBERT

Description: A partir de la firma del Proyecto de Gestión Pesquera DINARA-FAO (UTF/URU/025/URU), en septiembre de 2007, se comenzó a conformar una Unidad de Economía Pesquera. Sus objetivos se focalizaron en fortalecer la capacidad de recolección y análisis estadístico de la información socio-económica del sector. En el 2008 esta Unidad compiló y realizó un análisis de la información comprendida entre los años 2002 y 2007, reanudando luego de varios años esta publicación histórica. La misma fue un éxito en todo sentido, especialmente para consulta de los diferentes actores del sector. La aceptación y receptividad que ha tenido dicha publicación nos motiva y obliga a continuar en esta línea, rumbo a la obtención de un producto de valor y utilidad, basado exclusivamente en información oficial nacional. Este año retomamos la serie anual poniendo nuevamente a disposición de todos información actualizada, completa y de calidad que estamos seguros será nuevamente de gran beneficio para el sector público como privado, así como de interés para el público en general.

Description: Published

Description: Durante las últimas décadas se ha observado un incremento de la captura (descartada y retenida) de condrictios en las pesquerías artesanales e industriales, conjuntamente con un rápido crecimiento de las pesquerías no reguladas, lo cual ha ocasionado una disminución en muchas poblaciones de este grupo de peces en todos los mares del mundo. La sobrepesca y los elevados niveles de mortalidad ocasionados por la captura incidental, asi como la degradación y contaminación de áreas costeras donde se ubican las zonas de alimentación, reproducción y cría para muchas especies de condrictios, han colocado a este grupo de peces en una situación difícil. Estos hechos, combinados con el bajo potencial reproductivo y la estrategia de vida de la mayoría de las especies de condríctios, no permiten una recuperación de las poblaciones, cuando las mismas se ven enfrentadas a períodos de sobreexplotación. En las aguas de Uruguay ocurren aproximadamente 100 especies de condrictios, muchas de las cuales son capturadas por diferentes pesquerias, tanto de forma incidental como dirigida. Debido a la preocupación a nivel internacional sobre la sustentabilidad de las pesquerías de tiburones, la FAO en 1998 realizó una consulta internacional a expertos y desarrolló un “Plan de Acción Internacional para la Conservación y el Manejo de los Tiburones” (PAI - Tiburones), el cual fue adoptado en 1999. El objetivo del PAI - Tiburones es asegurar la conservación, el manejo y el uso sustentable a largo plazo de los tiburones. Al hacer referencia a “tiburones”, se incluyen a todos los condrictios (tiburones, batoideos y quimeras). Este documento se divide en dos Capítulos y cuatro Anexos. El primer capítulo incluye los objetivos del PAN - Condrictios Uruguay y las medidas propuestas para alcanzar los mismos. El segundo capítulo contiene un diagnóstico general de los condrictios, las pesquerías y el marco jurídico. Como anexos se incluyen una lista de especies de condrictios citadas para Uruguay junto a su status en las listas rojas de la UICN, una reseña biológica de las especies consideradas prioritaras, una lista de abreviaturas, y listas de instituciones y personas que participaron de las reuniones desarrolladas durante el proceso de elaboración del PAN – Condrictios Uruguay. Las medidas propuestas por el PAN - Condrictios Uruguay se deberán aplicar a todas las pesquerías efectuadas por buques de bandera uruguaya, incluso los que operan fuera de la zona económica exclusiva de Uruguay.

Description: Published

Description: chondrichthyan, legal norm

Description: La captura incidental en pesquerías comerciales ha sido identificada como una de las principales amenazas para la conservación de este grupo de aves, siendo los albatros (familia: Diomedeidae) y los petreles (familia: Procellariidae) las especies más afectadas. Debido a que los albatros y petreles presentan una gran longevidad y una baja fecundidad, pocas crías y un lento desarrollo, sus poblaciones son muy sensibles al aumento en la tasa de mortalidad causado por la captura incidental en las pesquerías. Anualmente son capturadas y muertas miles de aves marinas en las pesquerías comerciales que operan con diferentes configuraciones de palangre alrededor del mundo. Este arte, entre otras causas, está contribuyendo al descenso de varias poblaciones de albatros y preteles, configurando un claro riesgo de extinción de estas especies, si se permite que las tendencias actuales persistan. Las pesquerías de arrastre también interactúan con las aves marinas provocando la mortalidad de las mismas en un importante número. Otras pesquerías que capturan aves marinas son las que operan con redes de enmalle, redes de cerco y poteras. Respondiendo a la necesidad de reducir la mortalidad de aves marinas la Organización de las Naciones Unidas para la Agricultura y la Alimentación (FAO) desarrolló un Plan de Acción Internacional para Reducir la Captura Incidental de Aves Marinas en las Pesquerías de Palangre, el cual propicia la elaboración de Planes de Acción Nacionales en cada uno de sus países miembros. El objetivo del Plan de Acción Nacional – Aves Marinas de Uruguay es presentar un marco general que permita instrumentar medidas para la reducción de la captura incidental de aves marinas en todas las pesquerías de Uruguay.

Description: Published

Description: seabirds

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2007

Description: Oceanic spreading centers are sites of magmatic, tectonic, and hydrothermal processes. In this thesis I present experimental and seismological constraints on the evolution of these complex regions of focused crustal accretion and extension. Experimental results from drained, triaxial deformation experiments on partially molten olivine reveal that melt extraction rates are linearly dependent on effective mean stress when the effective mean stress is low and non-linearly dependent on effective mean stress when it is high. Microearthquakes recorded above an inferred magma reservoir along the TAG segment of the Mid-Atlantic Ridge delineate for the first time the arcuate, subsurface structure of a long-lived, active detachment fault. This fault penetrates the entire oceanic crust and forms the high-permeability pathway necessary to sustain long-lived, high-temperature hydrothermal venting in this region. Long-lived detachment faulting exhumes lower crustal and mantle rocks. Residual stresses generated by thermal expansion anisotropy and mismatch in the uplifting, cooling rock trigger grain boundary microfractures if stress intensities at the tips of naturally occurring flaws exceed a critical stress intensity factor. Experimental results coupled with geomechanical models indicate that pervasive grain boundary cracking occurs in mantle peridotite when it is uplifted to within 4 km of the seafloor. Whereas faults provide the high-permeability pathways necessary to sustain high-temperature fluid circulation, grain boundary cracks form the interconnected network required for pervasive alteration of the oceanic lithosphere. This thesis provides fundamental constraints on the rheology, evolution, and alteration of the lithosphere at oceanic spreading centers.

Description: Research was funded by a MIT Presidential Fellowship and NSF grants OCE-0095936, OCE-9907224, OCE-0137329, OCE-6892222, and OCE-6897400.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution December 1997

Description: A new tomographic technique is employed to investigate the structure and dynamics of the Pacific upper mantle. We invert band-center travel times of ScS reverberations and frequency-dependent travel times of direct S phases, upper-mantle guided waves such as SS and SSS, and the R1 and G1 surface waves for the 2D composite structure in the plane of two Pacific corridors. The frequency-dependent travel times of the turning and surface waves are measured from all three components of ground motion as phase delays relative to a radially-anisotropic, spherically-symmetric oceanic mantle model, and their 2D Fréchet kernels are constructed by a coupled-mode algorithm. The travel times of the primary ScSn and sScSn phases and their first-order reverberations from the 410 and 660 discontinuities are measured as individual phases and the 2D Fréchet kernels for these band-limited signals are calculated using the paraxial ray approximation. The model parameters include shear-speed variations throughout the mantle, perturbations to radial shear-wave anisotropy in the uppermost mantle, and the topography of the 410 and 660 discontinuities. We construct vertical tomograms through two mantle corridors: one between the Tonga subduction zone and Oahu, Hawaii, which traverses the central Pacific Ocean; and the other between the Ryukyu subduction zone and Oahu, which samples the northern Philippine Sea, the western Pacific, and the entire Hawaiian swell. Tests demonstrate that the data sets for the two corridors resolve the lateral structure in the upper mantle with a scale length of a few hundreds kilometers and greater but that the resolving power decreases rapidly in the lower mantle. The model for the Tonga-Hawaii corridor reveals several interesting features, the most significant being a regular pattern of high and low shear velocities in the upper mantle between Tonga and Hawaii. These variations, which are well resolved by the data set, have a horizontal wavelength of 1500 km, a vertical dimension of 700 km, and an amplitude of about 3%, and they show a strong positive correlation with seafloor topography and geoid-height variations along this corridor. The geoid highs correspond to a series of northwest-trending swells associated with the major hotspots of the Society, Marquesas, and Hawaiian Islands. Where these swells cross the corridor, they are underlain by high shear velocities throughout the uppermost mantle, so it is unlikely that their topography is supported by thermal buoyancy. This result is substantiated by the model from the Ryukyu-Hawaii corridor, which exhibits a prominent, fast region that extends beneath the entire Hawaiian swell. This anomaly, which resides in the uppermost 200-300 km of the mantle, is also positively correlated with the undulations of the Hawaiian-swell height. The other dominant features in the Ryukyu-Hawaii model include the high-velocity subducting slabs beneath the Ryukyu and Izu-Bonin seismic zones, which extend throughout the entire upper mantle; a very low-velocity in the uppermost 160 km of the mantle beneath the northern Philippine Sea, which is ascribed to the presence of extra water in this region; and a pronounced minimum in the amount of radial anisotropy near Hawaii, which is also seen along the Tonga-Hawaii corridor. A joint inversion of the data from the two corridors reveals the same anomaly pattern and clearly demonstrates that the swells in the Central Pacific are underlain by fast velocities. It is therefore implied that the topography of the swells in the central Pacific is supported by a chemical buoyancy mechanism which is generated by basaltic volcanism and the formation of its low-density peridotitic residuum. While the basaltic depletion mechanism can produce high shear velocities in the uppermost 200 km, it cannot explain the depth extent of the fast anomalies beneath the swells which, along Tonga-Hawaii corridor, extend well into the transition zone. It is therefore hypothesized that the central Pacific is underlain by a system of convective rolls that are confined above the 660-km discontinuity. It is likely that these rolls are predominantly oriented in the direction of plate motion (like "Richter rolls ") but the limited depth of the fast anomaly beneath the Hawaiian swell (200-300 km) suggests that their pattern is probably more complicated. Nevertheless, this convection pattern appears to be strongly correlated with the locations of the Tahitian, Marquesan, and Hawaiian hotspots, which raises interesting questions for Morgan's hypothesis that these hotspots are the surface manifestations of deep-mantle plumes.

Description: This research was supported by the National Science Foundation under grant EAR- 9628351 and by the Defense Special Weapons Agency under grant DSW A-F49620-95-1- 0051.

Description: Submitted in partial fulfillment of the requirements of the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2004

Description: Laterally extensive, well-developed clinoforms have been mapped in Early Cretaceous deposits located in the northeastern 27,000 km2 of the Colvile Basin, North Slope of Alaska. Using public domain 2-D seismic data, well logs, core photographs, and grain size data, depositional geometries within the Nanushuk and Torok formations were interpreted in order to constrain the transport conditions associated with progradation of the shoreline and construction of the continental margin out of detritus shed from the ancestral Brooks Range. Using STRATA, a synthetic stratigraphic modeling package, constructional clinoform geometries similar to those preserved in the North Slope clinoform volume (32,400 km3) were simulated. Sediment flux, marine and nonmarine diffusivities, and basin subsidence were systematically varied until a match was found for the foreset and topset slopes, as well as progradation rates over a 6 milion year period. The ability of STRATA to match the seismically interpreted geometries allows us to constrain measures of possible water and sediment discharges consistent with the observed development of the Early Cretaceous c1inoform suite. Simulations indicate that, in order to reproduce observed geometries and trends using constant input parameters, the subsidence rate must be very small, only a fraction of the most likely rate calculated from the seismic data. Constant sediment transport parameters can successfully describe the evolution of the prograding margin only in the absence of tectonic subsidence. However, further work is needed to constrain the absolute magnitude of these values and determine a unique solution for the NPR-A clinoforms.