989 research outputs found

    The report of the southern Western Australian Shark working group.

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    The southern Western Australian Shark Working Group was formed to investigate the southern shark fishery and advise the Minister for Fisheries on options for future management. Membership comprised six fishermen from regional professional fishermen\u27s associations and two Fisheries Department officers. The Working Group considered that each shark fisherman obtaining an entitlement should then be restricted in the length of fishing gear he can use and the number of months he can fish. The individual\u27s time and gear entitlement would be approximately that length of gear being used and time spent fishing in a period shortly before the bench mark date. To give more flexibility a fisherman should be allowed to nominated, at short notice, the particular month(s) be wishes to fish. These entitlements should be fully transferable. To ensure the minimum disruption to their activities supplementary access has also been proposed for fishermen who occasionally fish for shark

    Management measures for the Shark Bay snapper fishery 1987 season.

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    The 1986 Shark Bay snapper fishing season mirrored in almost all respects the situation which will apply when the limited entry regime is put into effect. It was thus an opportunity to assess how effective the measures recommended in the Report of the Shark Bay Snapper Fishery Working Group were in reducing effort in the fishery

    Draft management plan for the Perth Metropolitan Purse Seine Fishery

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    As part of a development strategy for inshore purse seine fishing along the Western Australian coast this plan proposes management measures for the purse seine fishing boats operating along the coast near the greater Perth Metropolitan area. Using as a basis the restricted entry Cockburn sound purse seine fishery, the plan proposes the introduction of a limited entry regime for inshore purse seine fishing between Lancelin to just south of Mandurah. This regime will permit management of the available pelagic fish stocks in the area and also protect the economic position of the existing participants by providing an environment for controlled development

    Future policy for charter fishing operations in Western Australia.

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    About 40 boats in Western Australia gain some of their income from taking recreational fishing parties out on charter. Half of these charter boats are also licensed commercial fishing boats. There are few Fisheries Department controls over charter boat fishing at present. However, with increasing tourism and leisure time, there are sound reasons for the Minister for fisheries to tighten up the controls over charter boat fishing to prevent over-exploitation in some areas or on particular stocks

    Fifth forces and discrete symmetry breaking

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    Modifications of general relativity often involve coupling additional scalar fields to the Ricci scalar, leading to scalar-tensor theories of Brans-Dicke type. If the additional scalar fields are light, they can give rise to long-range fifth forces, which are subject to stringent constraints from local tests of gravity. In this talk, we show that Yukawa-like fifth forces only arise for the Standard Model (SM) due to a mass mixing of the additional scalar with the Higgs field, and we emphasise the pivotal role played by discrete and continuous symmetry breaking. Quite remarkably, if one assumes that sufficiently light, non-minimally coupled scalar fields exist in nature, the non-observation of fifth forces has the potential to tell us about the structure of the SM Higgs sector and the origin of its symmetry breaking. Moreover, with these observations, we argue that certain classes of scalar-tensor theories are, up to and including their dimension-four operators, equivalent to Higgs-portal theories. In this way, ultra-light dark matter models may also exhibit fifth-force phenomenology, and we consider the impact on the dynamics of disk galaxies as an example

    Long term management measures for the Cockburn Sound restricted entry fisheries.

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    The objective of this management plan is to introduce rules which will ensure there is a real reduction in professional fishing units and fishing effort in the medium to long term. This reduction should enable a small professional fishery to co-exist with the recreational sector, supply fresh fish to the metropolitan area, ensuring there is no proliferation of shamateur fishing and providing a supply of recreational angling bait

    Further options for management of the Shark Bay Snapper Fishery : discussion paper.

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    A limited entry fishing regime for snapper was introduced in Shark Bay in order to constrain growth in fishing effort. Additional measures were introduced to reduce the number of vessels in the fishery, control areas fished and limit permitted fishing gear, with the ultimate objective of reducing catches from traditional fishing areas to long term sustainable levels

    The South West Trawl Fishery draft management plan.

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    This paper outlines a proposal for management of trawl fisheries operating in waters less than 200m deep between the Moore River north of Perth and Cape Leeuwin. Off Fremantle, potential and actual user conflicts between trawling and the requirements of recreational fishing and other forms of commercial fishing point to the need to gradually phase out trawling in this area. A limited entry fishery, with no licence transferability, is therefore proposed

    Kadanoff-Baym Approach to Flavour Mixing and Oscillations in Resonant Leptogenesis

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    We describe a loopwise perturbative truncation scheme for quantum transport equations in the Kadanoff-Baym formalism, which does not necessitate the use of the so-called Kadanoff-Baym or quasi-particle ansaetze for dressed propagators. This truncation scheme is used to study flavour effects in the context of Resonant Leptogenesis (RL), showing explicitly that, in the weakly-resonant regime, there exist two distinct and pertinent flavour effects in the heavy-neutrino sector: (i) the resonant mixing and (ii) the oscillations between different heavy-neutrino flavours. Moreover, we illustrate that Kadanoff-Baym and quasi-particle ansaetze, whilst appropriate for the flavour-singlet dressed charged-lepton and Higgs propagators of the RL scenario, should not be applied to the dressed heavy-neutrino propagators. The use of these approximations for the latter is shown to capture only flavour oscillations, whilst discarding the separate phenomenon of flavour mixing.Comment: 35 pages, 4 figures; further discussion added and typos corrected; final published versio

    Flavour Covariant Formalism for Resonant Leptogenesis

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    We present a fully flavour-covariant formalism for transport phenomena and apply it to study the flavour-dynamics of Resonant Leptogenesis (RL). We show that this formalism provides a complete and unified description of RL, consistently accounting for three distinct physical phenomena: (i) resonant mixing and (ii) coherent oscillations between different heavy-neutrino flavours, as well as (iii) quantum decoherence effects in the charged-lepton sector. We describe the necessary emergence of higher-rank tensors in flavour space, arising from the unitarity cuts of partial self-energies. Finally, within a Resonant Ï„\tau-Genesis model, we illustrate the importance of this formalism by showing that the final lepton asymmetry can vary by as much as an order of magnitude between partially flavour-dependent treatments, which do not capture all of the pertinent flavour effects.Comment: 7 pages, 2 figures; numerical example revised; Contribution to the Proceedings of the ICHEP 2014, Valencia, Spai
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