481 research outputs found
Protecting Marine Biodiversity: A Comparison of Individual Habitat Quotas (IHQs) and Marine Protected Areas
Fisheries managers in the United States are required to identify and mitigate the adverse impacts of fishing activity on essential fish habitat (EFH). There are additional concerns that the viability of noncommercial species, animals that are habitat dependent and/or are themselves constituents of fishery habitat may still be threatened. We consider a cap-and-trade system for habitat conservation, individual habitat quotas for fisheries, to achieve habitat conservation and species protection goals cost effectively. Individual quotas of habitat impact units (HIUs) would be distributed to fishers with an aggregate quota set to maintain a target habitat “stock” of EFH conservation. Using a dynamic, spatially explicit fishery simulation model we explore the efficiency and cost effectiveness of an IHQ policy versus alternative marine protected area (MPA) configurations, at reducing the risk of extinguishing a habitat dependent species of unknown spatial distribution. Our findings indicate that an IHQ policy with a conservatively established habitat target is better suited to the protection of non-target species than a rotating or fixed MPA policy.Fisheries management, Individual transferable quota, ITQ, Individual habitat quota, IHQ, Essential fish habitat, EFH, Marine protected areas, MPA, Non-target species
Extinction correction and on-sky calibration of SCUBA-2
Commissioning of SCUBA-2 included a program of skydips and observations of
calibration sources intended to be folded into regular observing as standard
methods of source flux calibration and to monitor the atmospheric opacity and
stability. During commissioning, it was found that these methods could also be
utilised to characterise the fundamental instrument response to sky noise and
astronomical signals. Novel techniques for analysing on-sky performance and
atmospheric conditions are presented, along with results from the calibration
observations and skydips.Comment: 10 pages, 7 figure
A Rigorous Free-form Lens Model of Abell 2744 to Meet the Hubble Frontier Fields Challenge
Hubble Frontier Fields (HFF) imaging of the most powerful lensing clusters
provides access to the most magnified distant galaxies. The challenge is to
construct lens models capable of describing these complex massive, merging
clusters so that individual lensed systems can be reliably identified and their
intrinsic properties accurately derived. We apply the free-form lensing method
(WSLAP+) to A2744, providing a model independent map of the cluster mass,
magnification, and geometric distance estimates to multiply-lensed sources. We
solve simultaneously for a smooth cluster component on a pixel grid, together
with local deflections by the cluster member galaxies. Combining model
prediction with photometric redshift measurements, we correct and complete
several systems recently claimed, and identify 4 new systems - totalling 65
images of 21 systems spanning a redshift range of 1.4<z<9.8. The reconstructed
mass shows small enhancements in the directions where significant amounts of
hot plasma can be seen in X-ray. We compare photometric redshifts with
"geometric redshifts", finding a high level of self-consistency. We find
excellent agreement between predicted and observed fluxes - with a best-fit
slope of 0.999+-0.013 and an RMS of ~0.25 mag, demonstrating that our
magnification correction of the lensed background galaxies is very reliable.
Intriguingly, few multiply-lensed galaxies are detected beyond z~7.0, despite
the high magnification and the limiting redshift of z~11.5 permitted by the HFF
filters. With the additional HFF clusters we can better examine the
plausibility of any pronounced high-z deficit, with potentially important
implications for the reionization epoch and the nature of dark matter.Comment: Accepted for publication in ApJ with newly identified lensed images
in complete HFF dat
Coupled economic-ecological models for ecosystem-based fishery management: Exploration of trade-offs between model complexity and management needs
Ecosystem based fishery management has moved beyond rhetorical statements calling for a more holistic approach to resource management, to implementing decisions on resource use that are compatible with goals of maintaining ecosystem health and resilience. Coupled economic-ecological models are a primary tool for informing these decisions. Recognizing the importance of these models, the International Council for the Exploration of the Seas (ICES) formed a Study Group on Integration of Economics, Stock Assessment and Fisheries Management (SGIMM) to explore alternative modelling approaches that bring the multiple disciplines of economics, ecology, and stock assessment into integrated ecosystem models. The theme session was designed to be an extension of a series of workshops and theme sessions organized by the SGIMM, but highlighted the economic component of coupled models. Although economic and ecological systems are inherently complex, models are abstractions of these systems incorporating varying levels of complexity depending on available data and the management issues to be addressed. The objective of this special session was to assess the pros and cons of increasing model complexity to incorporate linkages between ecosystem components and processes. While more complex ecosystem models may provide greater insight into how management decisions and human actions propagate through the ecosystem and impact the value of ecosystem services, the resources and information required to develop and parameterize them is greater and these models tend to require trade-offs such as the inability to quantify uncertainty or model human behaviour as accurately as can be done with models of individual fisheries. The theme session was organized as a moderated panel format representing a progression of economic-ecological models from less to increasingly complex. The panel was selected to represent a range of models from fully integrated, highly detailed and dynamic economic-ecological models such as Atlantis to models that may be less detailed or not fully dynamic or integrated. The special session focused primarily on management issues that are of a longer term strategic nature such as the implications of climate change, fundamental regime change, or the role of forage species in an ecosystem. Each panellist provided an overview of their model including the management questions the model was designed to address, the data and time requirements, as well as any lessons learned. The panellist presentations were followed by an open discussion among the panellists and the audience. The abstracts for each of the panellist presentation are provided below followed by a summary of the issues raised during the moderated discussion sessio
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Evolving Bycatch Risk in the Pacific Groundfish Trawl IFQ
Catches of several potential choke species in the Pacific groundfish IFQ are highly uncertain and tend to be concentrated while quota is broadly distributed. An analysis prior to implementation of the IFQ suggested substantial risk of individual vessels accidentally exceeding quota allocations for several rockfish species and Pacific halibut. Many fishermen lacked confidence that they would be able to acquire quota on the market to cover incidental catch and consequently joined risk pools to mitigate this risk. I update the analysis of bycatch risk using tow level catch data since implementation of the IFQ. The analysis indicates that expected catch rates of most choke species have declined suggesting more effective bycatch avoidance behavior. However, there remains a significant risk that vessels’ catch of some choke species can be several times median quota allocations, in part because many vessels have increased catch and effort by leasing quota pounds, but quota share ownership has remained distributed. The results underscore the importance of an efficient quota market to redistribute quota to match realized catches, but a recent analysis suggests that the quota market is not distributing quota effectively and is subject to high transactions costs. This provides and explanation for the persistence of risk pools despite the fact that aggregate catches of overfished rockfish species and Pacific halibut have remained well below total quotas.
Integrated System Health Management (ISHM): Systematic Capability Implementation
This paper provides a credible approach for implementation of ISHM capability in any system. The requirements and processes to implement ISHM capability are unique in that a credible capability is initially implemented at a low level, and it evolves to achieve higher levels by incremental augmentation. In contrast, typical capabilities, such as thrust of an engine, are implemented once at full Functional Capability Level (FCL), which is not designed to change during the life of the product. The approach will describe core ingredients (e.g. technologies, architectures, etc.) and when and how ISHM capabilities may be implemented. A specific architecture/taxonomy/ontology will be described, as well as a prototype software environment that supports development of ISHM capability. This paper will address implementation of system-wide ISHM as a core capability, and ISHM for specific subsystems as expansions and evolution, but always focusing on achieving an integrated capability
A Free-Form Prediction for the Reappearance of Supernova Refsdal in the Hubble Frontier Fields Cluster MACSJ1149.5+2223
The massive cluster MACSJ1149.5+2223(z=0.544) displays five very large lensed
images of a well resolved spiral galaxy at . It is within
one of these images that the first example of a multiply-lensed supernova has
been detected recently as part of the Grism Lens-Amplified Survey from Space.
The depth of this data also reveals many HII regions within the lensed spiral
galaxy which we identify between the five counter-images. Here we expand the
capability of our free-form method to incorporate these HII regions locally,
with other reliable lensed galaxies added for a global solution. This improved
accuracy allows us to estimate when the Refsdal supernova will appear within
the other lensed images of the spiral galaxy to an accuracy of 7\%. We
predict this supernova will reappear in one of the counter-images
(RA=11:49:36.025, DEC=+22:23:48.11, J2000) and on November 1 2015 (with
an estimated error of 25 days) it will be at the same phase as it was
when it was originally discovered, offering a unique opportunity to study the
early phases of this supernova and to examine the consistency of the mass model
and the cosmological model that have an impact on the time delay prediction.Comment: 12 images, 11 pages. Mateches accepted version in MNRAS. MNRAS in
pres
ISHM Implementation for Constellation Systems
Integrated System Health Management (ISHM) is a capability that focuses on determining the condition (health) of every element in a complex System (detect anomalies, diagnose causes, prognosis of future anomalies), and provide data, information, and knowledge (DIaK) "not just data" to control systems for safe and effective operation. This capability is currently done by large teams of people, primarily from ground, but needs to be embedded on-board systems to a higher degree to enable NASA's new Exploration Mission (long term travel and stay in space), while increasing safety and decreasing life cycle costs of systems (vehicles; platforms; bases or outposts; and ground test, launch, and processing operations). This viewgraph presentation reviews the use of ISHM for the Constellation system
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Impacts of the 2008-2009 US West Coast Salmon Ocean Fishery Closure on Salmon Troll Vessels
As anthropogenic changes interact with natural climate cycles, the variability of marine ecosystems is likely to increase. This variability influences the behaviour of fishers, which can affect the profitability and sustainability of stocks and may have wider economic and ecological effects. We use data from the US West Coast salmon troll fishery before, during, and after a large-scale closure to illustrate how altered resource availability influences the behaviour of fishing vessels in heterogeneous ways. We find that vessels were less likely to participate in fishing during the closure, with >40% of vessels ceasing fishing temporarily and 17% exiting permanently. Vessels that were more dependent on salmon were more likely to cease fishing, and more diversified vessels were more likely to continue. In spite of a high level of cross-participation, we find limited evidence that vessels increased their participation in other fisheries. Ports that obtained more of their revenue from salmon troll vessels saw larger decreases in their revenue during the closure. Overall, the closure was associated with a loss of ~$43 million in fishery revenue relative to the five year period before the closure. Based on our models and the composition of the current fleet, we predict that a closure in the near future would cause another economic disaster and lead to a large fraction of vessels exiting fishing. However, our results suggest that effects on fisheries linked by cross-participation are likely to be low.
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