Browsing by Author "Plagányi, Éva E"
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- ItemOpen AccessA History of recent bases for management and the development of a species-combined Operational Management Procedure for the South African hake resource(2008) Rademeyer, R; Butterworth, Doug S; Plagányi, Éva EThe bases for historical catch limits placed on the hake fishery are reviewed in brief for earlier years and then in some depth over the period from 1991 when the Operational Management Procedure (OMP) approach was introduced for this fishery. The new OMP implemented from 2007 was the first to be based on the use of rigorous species-disaggregated assessments of the resource as Operating Models. The paper describes the Reference Set and range of robustness trials, together with the associated Operating Models, which were used for the simulation testing of the new OMP. Performance statistics for a number of candidate OMPs are compared, and the two key trade-off decisions in the selection process discussed (substantial Merluccius paradoxus and catch per unit effort [CPUE] recovery, and total allowable catch [TAC] stability constraints). Details of the OMP adopted and how its formulae depend on recent trends in CPUE and survey estimates of abundance are provided. OMP-2007, which is tuned to a median 20-year recovery target of 20% of pristine spawning biomass for M. paradoxus and a 50% increase in CPUE over the next 10 years, has been adopted for recommending hake TACs over the 2007–2010 period until the next scheduled major review. A set of general guidelines adopted for the process of possible overruling of recommendations from OMPs or bringing forward their reviews within an otherwise intended four-year cycle is detailed.
- ItemOpen AccessAbalone poaching confiscation trends for Zones A-D up until 2007(2007) Plagányi, Éva EPoaching confiscation data have been updated using all data currently available up until the end of May 2007. The data have been reworked in terms of a standard Model year y that is taken to run from October of year y-1 to September of year y. This was necessary for reasons of internal consistency in the assessment process which uses a Model year as thus defined.
- ItemOpen AccessAbalone spatial- and age-structured assessment model preliminary results for Zones A, B, C and D in 2007(2007) Plagányi, Éva EThis document provides preliminary results from fitting the abalone spatial- and agestructured production model (ASPM) to Zones/Subareas A, B, CNP, CP and D in combination (hereafter referred to as the “combined ABCD model”) using the updated 2007 data. The full details of the spatial- and age-structured production model are provided in Appendix 1 and 2 of this document (see also WG/AB/07/Jun/01). A summary of model parameters and some of the basic features of the model are given in Tables 1 and 2
- ItemRestrictedAbalone spatial- and age-structured assessment model preliminary results for Zones A, B, C and D in 2008(2008) Plagányi, Éva EA summary is presented of the results obtained from the 2008 Reference-case model 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- and age-structured production model (ASPM) are provided in previous documents (Plagányi and Butterworth 2007). The 2008 base-case model uses an updated CPUPE index, and differs from last year’s base-case in estimating one more parameter for Zone A (the historic catch multiplier). The results of an “Alternative Policing Efficiency index” model version are also presented, based on the “Pedro case” series as described in document SWG-AB17. Model base-case results estimate a pristine spawning biomass, B sp 0 (in tonnes), of 8185, 5735, 6765 and 9064 for Zones A, B, C and D respectively. The current (inshore+offshore) spawning biomasses of abalone in Zones A, B and D are estimated at ca. 33 %, 35 % and 13 % respectively of their pre-exploitation levels. The “nonpoached” CNP and “poached” CP areas of Zone C are estimated at ca. 5 % and 4 % respectively with the inshore region particularly depleted: the model predicts zero remaining abalone in the inshore CNP, CP and Zone D areas. Equivalent est8imates for Zones A and B are 16% and 32%. Natural mortality is reasonably estimated (e.g. 0.33 yr-1 for age 0 and 0.14 yr-1 for age 15+) and in Zones C and D, the additional mortality estimated for 0-yr old abalone (due to the ecosystem-change effect) corresponds to near zero current annual survival rates. Poaching is severely impacting the resource, with Zone A particularly impacted in recent years. The combined Zones A-D model-predicted 2008 poaching estimate is 580 MT and corresponds to the assumption that, on average, 23% of all poached abalone are confiscated.
- ItemOpen AccessAbalone spatial- and age-structured assessment model results for Zones A, B, C and D in 2005(2005) Plagányi, Éva E; Butterworth, Doug SA summary is presented of the results obtained from the 2005 Reference-case model 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- and age-structured production model (ASPM) are provided in Appendix 1. Model results estimate a pristine spawning biomass, Bsp 0 (in tonnes), of 11930, 6190, 6890 and 7900 for Zones A, B, C and D respectively. The current spawning biomasses of abalone in Zones A, B and D are estimated at ca. 38 %, 40 % and 28 % respectively of their preexploitation levels. The “nonpoached” CNP and “poached” CP areas of Zone C are estimated at ca. 23 % and 10 % respectively with the inshore region particularly depleted: the model predicts zero remaining abalone in the inshore CP area. Natural mortality is reasonably estimated and in Zones C and D, the additional mortality estimated for 0-yr old abalone (due to the ecosystem-change effect) corresponds to near zero current annual survival rates. Poaching is severely impacting the resource, with Zone A particularly impacted in recent years. The combined Zones A-D model-predicted 2005 poaching estimate of 1150 MT (corresponding to the assumption that, on average, 19% of all poached abalone are confiscated) is more than six times the legal 2005 commercial TAC for these zones.
- ItemRestrictedAspects of modelling Robben Island African Penguin Spheniscus demersus populations(2006) Plagányi, Éva E; Butterworth, Doug SCrawford et al. (2006) present relationships between the breeding success of Robben Island African penguins Spheniscus demersus and the abundances of both anchovy Engraulis encrasicolus and sardine Sardinops sagax. Based on their analysis, they suggest that the management of the purse-seine fishery should ensure adequate escapement of fish to maintain the combined biomass of anchovy and sardine above two million tons. Given that this potentially has important repercussions for the management of the pelagic fishery, their analyses have highlighted the importance of further and more detailed investigations into this issue. This paper provides a brief summary of some further considerations in this regard.
- ItemRestrictedAssessing the adequacy of current fisheries management under changing climate: a southern synopsis(Oxford University Press, 2011) Plagányi, Éva E; Weeks, Scala J; Skewes, Tim D; Gibbs, Mark T; Blamey, Laura K; Soares, Muri; Robinson, William M L; Poloczanska, Elvira S; Norman-Lopez, AnnaClimate change is likely to have a significant impact on both target and non-target marine stocks worldwide, with the concomitant need for management strategies capable of sustaining fishing in future. We use several southern hemisphere fisheries to highlight the likely impacts of climate change at a range of levels, from individual to population responses, as well as ecosystem ramifications. Examples span polar (Antarctic krill fishery), temperate (west coast pelagic fishery, abalone and rock lobster), and tropical (Torres Strait rock lobster) commercially important fisheries. Responses of these fisheries to either past observed environmental changes or projected future changes are used to deduce some anticipated implications of climate change for fisheries management, including economic impacts and governance considerations. We evaluate the effectiveness of current single-species assessment models, management strategy evaluation approaches and multispecies assessment models as future management tools to cope with likely climaterelated changes. Non-spatial stock assessment models will have limited ability to separate fishery effects from the impacts of climate change. Anthropogenic climate change is occurring at a time-scale relevant to current fisheries management strategic planning and testing. Adaptive management frameworks (with their feedback loops) are ideal for detecting and adapting to changes in target stocks
- ItemMetadata onlyAssessing the adequacy of current fisheries management under changing climate:a southern synopsis(ICES Journal of Marine Science, 2012) Plagányi, Éva E; Weeks, Scala J; Skewes, Tim D; Gibbs, Mark T; Blamey, Laura K; Soares, Muri; Robinson, William M L; Norman-Lopez, AnnaClimate change is likely to have a significant impact on both target and non-target marine stocks worldwide, with the concomitant need for management strategies capable of sustaining fishing in future. We use several southern hemisphere fisheries to highlight the likely impacts of climate change at a range of levels, from individual to population responses, as well as ecosystem ramifications. Examples span polar (Antarctic krill fishery), temperate (west coast pelagic fishery, abalone and rock lobster), and tropical (Torres Strait rock lobster) commercially important fisheries. Responses of these fisheries to either past observed environmental changes or projected future changes are used to deduce some anticipated implications of climate change for fisheries management, including economic impacts and governance considerations. We evaluate the effectiveness of current single-species assessment models, management strategy evaluation approaches and multispecies assessment models as future management tools to cope with likely climaterelated changes. Non-spatial stock assessment models will have limited ability to separate fishery effects from the impacts of climate change. Anthropogenic climate change is occurring at a time-scale relevant to current fisheries management strategic planning and testing. Adaptive management frameworks (with their feedback loops) are ideal for detecting and adapting to changes in target stocks
- ItemRestrictedAssessment of the South African Hake resource taking its two-species nature into account(National Inquiry Services Centre, 2008) Rademeyer, Rebecca A; Butterworth, Doug S; Plagányi, Éva EThe commercially valuable hake fishery off South Africa consists of two morphologically similar species, the shallow-water Cape hake Merluccius capensis and the deep-water Cape hake M. paradoxus. Because catch-and effort statistics collected from the fishery are not species-disaggregated, previous published quantitative assessment methods have treated the two hake species as one. Furthermore, recent evidence suggests that (although treated as two separate populations in past assessments) the South and West coasts components of each species form a single stock. This paper describes the development of the first fully species-disaggregated coast-wide baseline assessment of the South African hake resource. M. paradoxus is estimated to be currently at <10% of its pre-exploitation level whereas M. capensis is estimated to be well above its maximum sustainable yield level. By taking into consideration the primary sources of uncertainty in this assessment, a Reference Set of 24 operating models is developed to be used in Operational Management Procedure testing.
- ItemRestrictedA brief introduction to some approaches to multispecies/ecosystem modeling in the context of their possible application in the management of South African fisheries(National Inquiry Services Centre (NISC), 2004) Butterworth, Doug S; Plagányi, Éva EAspects of the potential application of multispecies/ecosystem modelling to advise the management of South African fisheries are discussed. In general, reliable predictive ability from such models is likely to be achieved sooner for top predators, because relatively fewer links need to be modelled. Accordingly, discussion concentrates on the deliberations of scientific workshops on modelling marine mammal – fisheries interactions held by two international marine mammal commissions during 2002. Five questions are posed, and some responses suggested, relating to the development of a framework for multispecies/ecosystem modelling to contribute to South African fisheries management: (1) should such models be used for testing or making decisions; (2) do they appreciably reduce uncertainties associated with single-species models; (3) are whole ecosystem or minimum realistic models more appropriate; (4) what computer software is best suited to implement such approaches; (5) what are the overall cost implications? Caution is expressed that general scientific acceptance of predictive reliability for such models (as required for their use for management) is unlikely in the short term, and will probably require considerable data collection and complex analysis at not insubstantial cost.
- ItemOpen AccessA comparison between ADAPT-VPA and ASPM-based assessments of the Gulf of Maine cod stock(2005) Butterworth, Doug S; Rademeyer, Rebecca A; Plagányi, Éva EADAPT-VPA and ASPM assessment methods are applied to the same data set for the Gulf of Maine cod stock to attempt to ascertain the reasons for the rather different results provided by past applications of the two approaches. A number of sensitivity tests for the ASPM assessment are also conducted. Results indicate the primary reasons for the past differences to be the longer period of data which the ASPM approach is able to take into account, and the fact that this approach estimates selectivity to be decreasing at larger ages whereas the ADAPT-VPA method assumes the selectivity at such ages to be flat. Arguments are presented that an ASPM-based assessment of this resource would provide a better basis for management advice than the current ADAPT-VPA method. Since the former consistently indicates current status of the resource to be appreciably better relative to the sp BMSY reference point than does the latter, such a suggestion has important implications for current management measures for the Gulf of Maine cod fishery.
- ItemRestrictedConditioning SMOM using the agreed calendar of observed changes in predator and krill abundance: a further step in the development of a management procedure for krill fisheries in area 48(2008) Plagányi, Éva E; Butterworth, Doug SThe updated version of the Spatial Multi-species Operating Model (SMOM) of krill-predatorfishery dynamics described in an accompanying paper is conditioned using the WG-SAM set of reference observations for Area 48 (the SAM calendar). Results are presented for two implementations of SMOM, one with the time series of krill abundance fixed on input, and the other incorporating an explicit model of krill dynamics. Additional versions of SMOM that may need to be conditioned are discussed. In general the two SMOM implementations are broadly successful in reproducing the direction and timing of observed changes in predator abundance. The main method of conditioning involved estimating a shape parameter (the “steepness”) of the predator-prey interaction formulation. The steepness values estimated suggest that penguins respond sooner than other predators to decreasing levels of krill abundance. Given data on fish catches, the model estimates the starting (1970) fish abundance level, with results suggesting that fish populations in several of the SSMUs are much reduced compared to their 1970 levels. The conditioned operating models presented here constitute a further step towards the development of a spatially-structured Management Procedure (MP) for the krill fishery by contributing to the set of such operating models to be used to simulation test candidate MPs for robust performance. The next step involves agreeing the relative plausibilities (weights) for the different operating models. An outline of suggested future steps in the MP development process is discussed.
- ItemRestrictedA critical look at the potential of Ecopath with ecosim to assist in practical fisheries management(National Inquiry Services Centre, 2004) Plagányi, Éva E; Butterworth, Doug SEcosystem-orientated thinking is increasingly incorporated into fishery management. Given the complexity of ecosystem processes, there is a need to evaluate the tools used to steer this thinking critically. ECOPATH with ECOSIM (EwE), an aggregate system-modelling package, is currently the most widely employed approach to assess the ecosystem effects of fishing. The basic equations and assumptions, strengths and weaknesses, and the potential of this approach to contribute to practical fisheries management advice are reviewed. Strengths include the structured parameterization framework, the inclusion of a well-balanced level of conceptual realism, a novel representation of predator-prey interaction terms, and the inclusion of a Bayes-like approach (ECORANGER) to take account of the uncertainty associated with values for model inputs. Weaknesses in model structure include the constraining nature of the mass-balance assumption (of ECOPATH) for initiating projections, the questionable handling of life history responses such as compensatory changes in the natural mortality rates of marine mammals, overcompensatory stock-recruit relationships that result from default parameter settings, possible problems in extrapolating from the microscale to the macroscale, as well as some (not too far-reaching) mathematical inconsistencies in the underlying equations. There is a paucity of systematic and stepwise investigations into model behaviour and properties, and users are cautioned against non-critical use of the default settings. An important limitation related to the predominant use of EwE as a "black-box" modelling tool is that some users fail to consider a range of alternative interaction representations. As with all multispecies approaches, the major limitation in applying the EwE approach lies in the quality and quantity of available data. Current EwE applications generally do not adequately address uncertainty in data inputs and model structure. Prudent EwE applications that utilize good data and are based upon rigorous statistical analyses can complement the quantitative predictions of traditional single-species models. They could be particularly useful in some contexts if output in the form of probability distributions encompassing a range of likely ecosystem responses were to be coupled with attempts to extend Operational Management Procedure (OMP) approaches to fisheries management beyond the singlespecies level. In particular, such applications could serve as the operating models of the underlying dynamics that are used for computer simulation testing of OMPs.
- ItemRestrictedData inputs for the African Penguin Spheniscus demersus model to be coupled to the pelagic OMP(2008) Plagányi, Éva E; Robinson, WilliamThis document serves as an updated compilation of all data currently available as inputs to the African penguin spatial model which is to be coupled to the pelagic OMP. The data are presented here together with some comments as to how they are to be used in the model and notes on their derivation and potential reliability. The model presented thus far is spatial in that different populations of penguins are represented, and different levels of movement between these populations are modelled. The main focus of the model is on Dassen and Robben Islands, which were originally combined for reasons of simplicity and because of their close proximity to each other, suggesting that the effects of external factors such as food availability would be highly correlated between the two. However, data that have recently become available indicate differences between these two colonies which suggest that it may no longer be appropriate to pool the two; hence they are split in the model. The third population is Dyer Island because it has the next largest numbers of penguins, recent declines in the population there are of concern and it is considered an important breeding site for penguins given the eastward shift of sardines. The fourth population is Boulders. Although relatively small, this colony was considered important to include because of its position, its role as the focus of several other studies and because penguins are known to have moved from Dyer Island to Boulders, Robben and Dassen, and hence it is useful to quantify to what extent movement of birds away from Dyer Island could account for observed declines at Dyer and increases at these other colonies. A summary of all the breeding colonies of penguins in so-called area i) is provided in Fig. 1 which also shows the relative abundance of breeding pairs in the different sub-areas, computed from data in Underhill et al. (2006). The regional penguin population is dominated (in terms of numbers) by two large colonies, namely Robben Island and Dassen Island; thus the model here has focused on these two colonies, with the next most important colony being Dyer Island. Fig. 2 maps the extent of strata corresponding to pelagic fish biomass estimates used to link to penguin breeding success in the model. Initially relationships were investigated with the west of Cape Agulhas pelagic spawner biomass and the west of Cape Infanta recruit abundances rather than the total South African pelagic fish abundance. More recently, this has been refined further still to use the Cape Columbine to Cape Point spawner biomass component only since this more accurately depicts the biomass available to penguins in the west coast model area. The west of Cape Infanta recruit estimates are retained because the anchovy and sardine recruits move down the West Coast. The model time step is one year and hence average trends are modelled. Penguins in each subarea are modelled starting from 1986.
- ItemRestrictedEcosystem modelling provides clues to understanding ecological tipping points(Inter Research, 2014) Plagányi, Éva E; Ellis, Nick; Blamey, Laura K; Morello, Elisabetta B; Norman-Lopez, Anna; Robinson, William M L; Sporic, Miriana; Sweatman, HughEcological thresholds, associated with abrupt changes in the state and organisation of ecosystems, challenge both scientists and managers. Adaptive response to such changes, and planning for their occurrence, requires an understanding of the underlying drivers and system responses as well as appropriate monitoring. In addition to field studies, modelling can advance our ability to anticipate or deal with such major ecosystem shifts. Here, we used an existing multispecies model with smooth continuous functions that were modified to include thresholds representing 3 alternative scenarios of predator responses when prey numbers drop below a critical threshold: (I) no threshold-like response; (II) an abrupt decrease in breeding success by 90%, and (III) an abrupt halving of adult survival. Second, we analysed field observations from 3 independent marine case studies (abalone, starfish, penguins) for evidence of abrupt non-linear responses of predators to changes in abundance of principal prey. Third, we compared the model output with empirical results and tested (using both a statistical method and by fitting multispecies models) the 3 alternative response scenarios. With this approach, we found evidence for nonlinear changes in population parameters (such as survival rate) of predators as prey numbers declined below critical thresholds. As an example of the potential for this approach to inform management, we found that abundances of a range of marine predators become more variable as prey numbers decline, which may be a useful indicator that a system is approaching a tipping point.
- ItemOpen AccessFurther results using the 2008 abalone assessment model for Zones A, B, C and D(2008) Plagányi, Éva EA summary is presented of the results obtained from the 2008 Reference-case model and three 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- and age-structured production model (ASPM) are provided in previous documents (Plagányi and Butterworth 2007). The 2008 base-case model uses an updated CPUPE index, and differs from last year’s base-case in estimating one more parameter for Zone A (the historic catch multiplier).
- ItemRestrictedA history of recent bases for management and the development of a species-combined Operational Management Procedure for the South African hake resource(National Inquiry Services Centre, 2010) Rademeyer, Rebecca A; Plagányi, Éva E; Butterworth, Doug SThe bases for historical catch limits placed on the hake fishery are reviewed in brief for earlier years and then in some depth over the period from 1991 when the Operational Management Procedure (OMP) approach was introduced for this fishery. The new OMP implemented from 2007 was the first to be based on the use of rigorous species-disaggregated assessments of the resource as Operating Models. The paper describes the Reference Set and range of robustness trials, together with the associated Operating Models, which were used for the simulation testing of the new OMP. Performance statistics for a number of candidate OMPs are compared, and the two key trade-off decisions in the selection process discussed (substantial Merluccius paradoxus and catch per unit effort [CPUE] recovery, and total allowable catch [TAC] stability constraints). Details of the OMP adopted and how its formulae depend on recent trends in CPUE and survey estimates of abundance are provided. OMP-2007, which is tuned to a median 20-year recovery target of 20% of pristine spawning biomass for M. paradoxus and a 50% increase in CPUE over the next 10 years, has been adopted for recommending hake TACs over the 2007–2010 period until the next scheduled major review. A set of general guidelines adopted for the process of possible overruling of recommendations from OMPs or bringing forward their reviews within an otherwise intended four-year cycle is detailed.
- ItemRestrictedIllegal and unreported fishing on abalone—Quantifying the extent using a fully integrated assessment model(Elsevier, 2011) Plagányi, Éva E; Butterworth, Doug S; Burgener, MarkusIllegal, unregulated and unreported (IUU) fishing is a major problem in many of the world's fisheries. The stocks most severely impacted centre on those characterised by high economic value, such as abalone, as well as long lived and slow growing species such as Patagonian toothfish (Dissostichus eleginoides). Effective management of these stocks as well as assessment of the impacts of IUU fishing on the resources is impeded by the technical difficulties associated with determining the magnitude of the IUU catches. The South African abalone Haliotis midae fishery rates as an extreme example of extraordinarily high levels of illegal and unreported (IU) catch. To assess the level and trends in IU catches, we used a combination of approaches that included collation of confiscation records from law enforcement, development of a novel index (the confiscations per unit policing effort—CPUPE), estimation of illegal catches using a spatial and age-structured assessment model, and cross-checking of model outputs through comparison with trade data on abalone imports in destination countries. The model-predicted 2008 IU estimate was 860 tonnes, more than 10 times the total allowable catch (TAC) for that year, and implied that, on average, 14% of all IU catches are confiscated. Associated management responses included the listing of H. midae on Appendix III of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora), and a temporary closure of the commercial fishery. We summarise both technical and management lessons to be learnt from this integrated approach to assess and verify the magnitude of IU fishing.
- ItemOpen AccessAn Illustrative Management Procedure for exploring dynamic feedback in krill catch limit allocations among small-scale management units(2006) Plagányi, Éva E; Butterworth, Doug S; Butterworth, Doug SA Management Procedure (MP) approach is proposed to assist in advising regarding the subdivision of the precautionary catch limit for krill among 15 small-scale management units (SSMUs) in the Scotia Sea to reduce the potential impact of fishing on land-breeding predators. The Spatial Multi-species Operating Model (SMOM) developed in Plaganyi and Butterworth (2006) is used as an operating model which simulates the “true” dynamics of the resource with tests across a wide range of scenarios for the underlying dynamics of the resource. Unlike static catch allocation options, the illustrative MPs developed here have a feedback structure, and hence are able to react and self-correct. It is important, as with the static allocation options, to ensure that the likely performances of these MPs in terms of low risk to predators within each SSMU are reasonably robust to the primary uncertainties about such dynamics. A MP module separate from the operating model contains the methods and rules that are used to subdivide the krill catch between SSMUs. Different MPs are then simulation tested with their performances being evaluated on the basis of a set of performance statistics which essentially compare the risks of reducing the abundances of predators (and krill) below certain levels, as well as the variability in future average krill catches per SSMU associated with each MP. The key assumption made here is that data will be regularly available in future to monitor the impact/s of different krill catch limits. For illustrative purposes, it is assumed that two main sources of data will be available for use in a MP: (1) indices of absolute or relative abundance, or performance of the various predators (i.e. the CEMP series), and (2) survey estimates of krill absolute or relative abundance per SSMU. The approach proposed is readily modified if, for example, no krill abundance indices are available. Given that “future” data are required as inputs to test a MP including feedback, these data are generated with random variation about their underlying values and assuming the same variance as estimated from the past data
- ItemOpen AccessIllustrative outputs of the age-structured model of African penguin populations for linking to the pelagic OMP testing process(2008) Robinson, William M L; Plagányi, Éva E; Butterworth, Doug SGiven the move towards adopting an ecosystem approach to fisheries in the pelagic sector, the new joint OMP needs to be tested in the light of not only the risk parameters as considered previously, along with catch statistics, but also parameters denoting risk to the African penguin population(s) Spheniscus demersus. Penguins have been chosen as a key predator species to consider because of their conservation status, and because of their potential sensitivity to changes in pelagic fish abundance and distribution as a consequence of their land-based breeding sites. A model of penguin dynamics has been developed for use as a penguin Operating Model to be coupled to the pelagic fish OMP. This paper summarises the base-case penguin model and proposed method for use in evaluating the impact on penguins of predicted future pelagic fish trajectories under alternative harvest strategies (OMPs).