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Browsing by Author "Plagányi, Éva E"

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Investigating the consequences of Marine Protected Areas for the South African deep-water hake (Merluccius paradoxus) resource

Author: Edwards, Charles T T ; Rademeyer, Rebecca A ; Butterworth, Doug S ; Plagányi, Éva E Date: 2009 Protected areas are often touted as important management tools to mitigate the uncertainty inherent in marine ecosystems, and thereby improve the long-term prospects for sustainable resource use. However, although they certainly play an ... Read more
Investigating the use of interview data regarding the illegal sector in the stock assessments for abalone in Zones E and G

Author: Edwards, Charles ; Hauck, Maria ; Plagányi, Éva E Date: 2007 Read more
Leslie matrix based estimates of maximum growth rate for the African penguin population

Author: Butterworth, Doug S ; Plagányi, Éva E Date: 2007 Log linear regressions of breeder numbers of African penguins over 1996-2005 for Robben Island and the Western Cape as a whole (ASWS/JUL07/PENG/DAT/1, Table 1) reflect annual increase rates of 11.4% and 9.6% respectively. How consistent are ... Read more
Making management procedures operational—innovations implemented in South Africa

Author: Plagányi, Éva E ; Rademeyer, Rebecca A ; Butterworth, Doug S ; Cunningham, Carryn L ; Johnston, Susan J Date: 2007 Operational management procedures (OMPs) have become an indispensable fisheries management tool in South Africa in light of their ability to consider the consequences of the main sources of assessment uncertainty. An overview is provided of ... Read more
Management procedures for the South African hake resource in the 2000s

Author: Rademeyer, Rebecca A Date: 2012 The two-species South African hake fishery (deep-water Merluccius paradoxus and shallow-water M. capensis) has been managed using Operational Management Procedures (OMPs) since 1990. This thesis summarises the development of two OMPs: OMP-2007, ... Read more
Modeling a regime shift in a kelp-forest ecosystem caused by a lobster range expansion

Author: Blamey, Laura K ; Plagányi, Éva E ; Branch, George M Date: 2013 The South African West Coast rock lobster, Jasus lalandii (H. Milne-Edwards, 1837), has expanded its range to the southeast, where its abundance has increased radically. The ecological consequences of this “invasion” are likely to be considerable. ... Read more
Multi-species considerations in planning methodologies for possible joint South African-Namibian hake assessments

Author: Plagányi, Éva E ; Butterworth, Doug S ; Rademeyer, Rebecca A Date: 2006 There are increasing pressures for an EAF (an Ecosystem Approach to Fisheries - Garcia et al. 2003) both in South Africa and Namibia as well as world-wide. The management of the major South African and Namibian fisheries is currently based ... Read more
Multi-species models of Antarctic krill predators : do competitive effects influence estimates of pre-exploitation whale abundance and recovery?

Author: Mkango, Sara Date: 2008 Includes abstract. Includes bibliographical references (leaves 92-111). Read more
Observer effects on pelagic fleet operations and Bayesian-based explorations of the mass balance model ECOPATH

Author: Somhlaba, Sobahle Date: 2006 This thesis comprises two sections. The first deals with the analysis of observer data from pelagic commercial vessels with a particular focus being to examine whether there is any indication of dumping (discarding) that is provided by these ... Read more
Participatory assessment of the South African abalone resource and its impact on predicted population trajectories

Author: Edwards, Charles T T ; Plagányi, Éva E Date: 2008 Illegal harvesting is a cause for concern in many of the world's fisheries. Over the last decade, the abalone resource in South Africa has come under severe fishing pressure, largely because of increased and unmitigated levels of poaching. ... Read more c b
Preliminary analysis of catch-per-unit-effort data for abalone in Zones A-D

Author: Plagányi, Éva E Date: 2008 The General Linear Model (GLM) approach used last year needs to be updated for use in standardising the commercial abalone CPUE time series (1980 – 2006) of abalone for the influence of other factors on the CPUE apart from resource abundance. ... Read more
Preliminary GLM standardisation of the commercial CPUE series for abalone in Zones E and G from 1980 to 2007

Author: Edwards, Charles ; Plagányi, Éva E ; Butterworth, Doug S Date: 2007 The commercial CPUE series is considered during modeling of resource dynamics as an index of population abundance. However, a number of factors other than abundance may influence recorded values. Where sufficient data exists, General Linear ... Read more
Preliminary model of the impact of pelagic fishing on the South African west coast in the vicinity of seal and penguin colonies

Author: Plagányi, Éva E Date: 2005 Preliminary work is summarised here concerning the development of a model of the impact of pelagic fishing on the South African west coast in the vicinity of seal and penguin colonies, for report to the CCAMLR Scientific Committee to parallel ... Read more
Proposed performance statistics for evaluating the effects of pelagic fishing on African Penguin populations

Author: Plagányi, Éva E ; Robinson, William Date: 2008 Given the move towards adopting an ecosystem approach to fisheries in the pelagic sector, the new pelagic OMP needs to be tested in the light of not only the risk parameters as considered previously, along with catch statistics for the anchovy ... Read more
Reference-case 2008 assessment model for abalone in Zones A, B, C and D

Author: Plagányi, Éva E Date: 2008 A summary is presented of the results obtained from the 2008 Reference-case model and two variants that was fit to Zones A, B, CNP, CP and D in combination (hereafter referred to as the “combined ABCD model”). The full details of the spatial- ... Read more
Report on an investigation of reasons for differences between outputs from ASPM and ADAPT-VPA assessments of the Gulf of Maine cod stock

Author: Butterworth, Doug S ; Rademeyer, Rebecca A ; Plagányi, Éva E Date: 2005 The application of ADAPT-VPA and ASPM assessment methods to the same data set for the Gulf of Maine cod stock allows two primary reasons for earlier differences in assessment results from these two approaches to be identified: • the longer ... Read more
Response to MCM/2010/PEL/48: Suggestions for improving the penguin modeling framework

Author: Butterworth, Doug S ; Robinson, William M L ; Plagányi, Éva E ; de Moor, Carryn L Date: 2010 As general background, it should be noted that the brief for document MCM/2010/SWG-PEL/35 was to combine into a single convenient reference a number of documents that contributed to the discussion and decision on the issue of possibly amending ... Read more
Results for an illustrative empirical decisison rule for hake projections for C3 scenarios in the context of alternative options for initial TAC reduction levels

Author: Rademeyer, Rebecca A ; Plagányi, Éva E ; Butterworth, Doug S Date: 2005 This paper reports further investigations of the performance of an illustrative EMPIRICAL decision rule (OMP) for the hake resource for C3 scenarios only because these reflect (on average) a current spawning biomass ratio for M. capensis ... Read more
Retrospective and exploratory analyses using the abalone ASPM for Zones A-D

Author: Plagányi, Éva E ; Butterworth, Doug S Date: 2008 The following exploratory analyses were done using the 2007 abalone assessment model Read more
Review of the causes of the rise of the illegal South African abalone fishery and consequent closure of the rights-based fishery

Author: Raemaekers, Serge ; Hauck, Maria ; Burgener, Markus ; Mackenzie, Angus ; Maharaj, Genevieve ; Plagányi, Éva E ; Britz, Peter J Date: 2011 The rise of organised illegal fishing and trade in abalone from the late 1990s destabilised South Africa’s historically stable, quota-managed fishery, culminating in its closure in 2008. The development of the fishery is described in a ... Read more c b n d

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