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Zang A.R.,VISGRAF Laboratory | Felinto D.,Fisheries Center | Velho L.,VISGRAF Laboratory
SIGGRAPH Asia 2012 Posters, SA 2012

Ask for a programmer and an artist what is the Holy Grail of computer graphics and you may hear completely different answers. It is part of the competence of computers to strive for reproducing reality, to mimic it bit by bit, photon by photon. It is in the core of graphics to go beyond and expand our experience of the reality with the creative input of the artist. In this project we are trying to combine both views of the field of computer graphics expanding the possibilities of photo-realistic rendering of synthetic elements combined with a captured environment. Our work is focused on (but not exclusive to) full panorama renders. The novelty of our method is the use of light-depth maps to increase the accuracy in the rendering process, as presented in our previous work [Felinto et al. 2012]. Panorama images have been extensively used in the past. As a final representation of a set, a background plate, as reflection maps, as environment light maps or even to support the modeling of the environment geometry. However, panoramas with the light field representation when combined with the scene geometry can achieve rendering calculations not yet explored. Those particular sets of panoramas are here called light-depth maps. The intent of this project is to show how they can produce more accurate photorealistic rendering of shadows, light and reflections for synthetic elements inserted in a captured scene than its current alternatives. The relevance of this project is reinforced by the growing demand for panorama content production. This is in part due to the modernization of old planetariums into digital fulldome projection systems, the existence of panorama capturing devices such as Gigapan and LadyBug and new gyroscope friendly consumer devices and applications such as Google Street View, and the soon to be released Nintendo Wii U Panorama View. Additionally, panoramas can be used for traditional film-making aimed at conventional displays. light-depth maps can be built in affordable ways and increase the quality of the augmented reality rendering productions. Copyright is held by the author / owner(s). Source

Gurney L.J.,Ocean and Atmospheric Science | Pakhomov E.A.,Ocean and Atmospheric Science | Christensen V.,Fisheries Center
Ecological Modelling

A model of an ecosystem provides a useful tool for the exploration of management options to achieve desired objectives. With the move to a more holistic approach to marine resource management, ecosystem models and the indicators that can be derived using them, are providing a means to move away from single species management and allow for the ecosystem effects of population dynamics to be explored. This work describes the construction of an ecosystem model of the Prince Edward archipelago. The archipelago consists of two islands, Marion and Prince Edward, which are situated southeast of the southern tip of Africa at 46°46'S, 37°51'E. The islands are host to millions of seabirds and seals that use the islands as a refuge for breeding and moulting. Using the Ecopath software, the ecosystem is described across three separate decades (1960s, 1980s, 2000s). All trophic links are described based on the rich published literature that exists for the islands. Local survey data for population estimates and trophic linkages were sourced for defining and quantifying the food web. The system is summarised into 37 functional groups which include 4 primary producer groups at the lower trophic spectrum, and 14 land based top predator groups (seals and seabirds) representing the majority of the higher trophic levels. Two detrital groups are included. The food web is compared across the three time periods with transfer efficiencies declining for the higher trophic levels through time, suggesting a decline in energetic coupling between groups. Comparison of the PEI ecosystem with eight other modeled sub Antarctic/Antarctic systems showed the ecosystem size (as measured in total biomass throughput per year, year-1) to be lower than all other systems and was found to be most similar to the Kerguelen Islands for the ecological metrics assessed. Future research priorities are highlighted based on an assessment of data availability, data gaps and sensitivity testing. The construction of this model provides a much needed tool for the advancement of management for the archipelago, which have both fisheries and conservation concerns. © 2014 Elsevier B.V. Source

Okamura H.,Japan National Research Institute of Fisheries Science | McAllister M.K.,Fisheries Center | Ichinokawa M.,Japan National Research Institute of Fisheries Science | Yamanaka L.,Pacific Biological Station | Holt K.,Pacific Biological Station
Fisheries Research

Offshore lingcod (Ophiodon elongatus) in British Columbia (BC) make seasonal migrations that differ by sex: in winter most adult males aggregate in shallow water and most adult females aggregate in deep water, while in summer both sexes distribute equally in deep and shallow water. We developed a semi-age structured delay-difference model that accommodates sex-, and age/depth-specific seasonal migration and examined the sensitivity of biological reference points for BC offshore lingcod to migration pattern and the allocation of fishing effort across seasons and depths. When a migration pattern with a homogeneous distribution of males and females in shallow and deep water throughout the year was assumed, the estimated maximum sustainable yield (MSY), biomass at MSY (BMSY), and percent spawning per recruitment at MSY (%SPRMSY) were robust to changes in effort allocation. However, when a migration pattern that assumed a winter distribution of 95% of adult males in shallow water and 95% of adult females in deep water was used, the estimated MSY, BMSY, and %SPRMSY were markedly sensitive to changes in effort allocation. These results suggest that incorporating sex-, age/depth-, and season-specific structuring in stock assessment models could enable improved evaluations of management options for BC lingcod and other species with sex- and season-specific migrations. © 2013 Elsevier B.V. Source

Kerby T.K.,University of East Anglia | Kerby T.K.,CEFAS - Center for Environment, Fisheries and Aquaculture Science | Cheung W.W.L.,University of East Anglia | Cheung W.W.L.,CEFAS - Center for Environment, Fisheries and Aquaculture Science | And 2 more authors.
Reviews in Fish Biology and Fisheries

This study compiles 100 years of North Sea demersal landings, focusing on the UK, and relating them to historical events and political, technological and economical drivers that influenced demersal fisheries. In the early twentieth century, aided by technological advances, the UK, and in particular England, had unchallenged dominance in North Sea demersal fisheries. Since then, the two World Wars and other political developments have had a great impact on British fisheries. Between the 1920s and 1960s, English ports shifted their interests away from the North Sea towards highly profitable distant waters, whereas the Scottish fleet relied less on these fishing grounds. Meanwhile, especially in the 1960s, other European countries expanded their fisheries, undermining Britain's lead. In the 1970s and 1980s, Scotland benefitted from mainly fishing in the North Sea. Firstly, the assertion of 200 nautical miles Exclusive Economic Zones made the distant waters inaccessible to English fleets at a time when England's fisheries were highly dependent on them. Secondly, the relatively minor activity in the North Sea by the English compared to the Scottish fleets coincided with the establishment of the Common Fisheries Policy. This had implications when total allowable catches were first implemented because quota allocations to countries were based on their recent catches from the North Sea. Thus, after the loss of fishing opportunities in distant waters, the North Sea once more became an important fishing ground for Britain, just as in the early twentieth century, however, the emphasis of fisheries had shifted from England to Scotland. © 2012 Her Majesty the Queen in Rights of the United Kingdom. Source

McGregor A.M.,University of Alberta | McGregor A.M.,Environment Canada | Davis C.L.,Ontario Ministry of Natural Resources | Walters C.J.,Fisheries Center | Foote L.,University of Alberta
Ecology and Society

Increased population sizes of Double-crested Cormorants (Phalacrocorax auritus) and small-bodied (<15 cm total length) yellow perch (Perca flavescens) have occurred at Lac la Biche, Alberta, Canada, since fisheries collapsed the walleye (Sander vitreus) population. A walleye restoration program was introduced in 2005, but uncertainty around the ecosystem’s response to management made it difficult to evaluate program success. This study used 40 variations of Ecopath with Ecosim models representing ecosystem conditions over 200 years to test the potential for multiple attractors, i.e., possible ecosytem states, in a large lake ecosystem. Results suggest that alternate stable states, defined by walleye-dominated and cormorant-dominated equilibriums, existed in historical models (1800, 1900), whereas contemporary models (1965, 2005) had a single cormorant-dominated attractor. Alternate stable states were triggered by smaller perturbations in 1900 than in 1800, and model responses were more intense in 1900, suggesting a decline in system resilience between model periods. Total prey biomass consumed by walleye was up to four times greater than the biomass consumed by cormorants in historical models, but dropped to 10% of cormorant consumption in 2005 models. Differential size-selection pressures of cormorants and walleye on yellow perch provided strong feedback that stabilized each state. These results provide important theoretical support for alternate stable states as well as practical insights for restoration of large lake ecosystems affected by human induced overharvest of top-level fish predators. © 2015 by the author(s). Source

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