Browsing by Subject "management strategy evaluation"

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    Fisheries management under climate and environmental uncertainty: control rules and performance simulation
    (Oxford University Press, 2014) Punt, Andre´ E; A’mar, Teresa; Bond, Nicholas A; Butterworth, Doug S; de Moor, Carryn L; De Oliveira, Jose´ A A; Haltuch, Melissa A; Hollowed, Anne B; Szuwalski, Cody
    The ability of management strategies to achieve the fishery management goals are impacted by environmental variation and, therefore, also by global climate change. Management strategies can be modified to use environmental data using the “dynamic B0” concept, and changing the set of years used to define biomass reference points. Two approaches have been developed to apply management strategy evaluation to evaluate the impact of environmental variation on the performance of management strategies. The “mechanistic approach” estimates the relationship between the environment and elements of the population dynamics of the fished species and makes predictions for population trends using the outputs from global climate models. In contrast, the “empirical approach” examines possible broad scenarios without explicitly identifying mechanisms. Many reviewed studies have found that modifying management strategies to include environmental factors does not improve the ability to achieve management goals much, if at all, and only if the manner in which these factors drive the system is well known. As such, until the skill of stock projection models improves, it seems more appropriate to consider the implications of plausible broad forecasts related to how biological parameters may change in the future as a way to assess the robustness of management strategies, rather than attempting specific predictions per se.
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    Management strategy evaluation for Greenland halibut (Reinhardtius hippoglossoides) in NAFO Subarea 2 and Divisions 3LKMNO
    (2008) Miller, David C M; Shelton, Peter A; Healey, Brian P; Brodie, William B; Morgan, Joanne M; Butterworth, Doug S; Alpoim, Ricardo; González, Diana; González, Fernando; Fernandez, Carmen; Ianelli, James; Mahé, JeanClaude; Mosqueira, Iago; Scott, Robert; Vazquez, Antonio
    A rebuilding plan for the 2+3KLMNO Greenland halibut stock developed by NAFO Fisheries Commission has been in effect since 2004. Under the plan, ad hoc TAC reduction steps were specified to 2007. The most recent assessment of this stock indicates that the rebuilding plan has been ineffective in initiating any recovery. Fishing mortality is still at high levels and spawner biomass has remained at very low levels. Management Strategy Evaluation provides a way of examining the performance of candidate management strategies with respect to rebuilding the stock. In particular, it allows the robustness of these strategies to be considered relative to alternative operating models of the “real world”, for example the nature of the stock-recruit function for this stock. A preliminary MSE presented at the 2007 NAFO Scientific Council meeting has been updated following the NAFO SC Study Group on Rebuilding Strategies for Greenland Halibut meeting held in Vigo in February 2008. The analysis is carried out in FLR (Fisheries Libraries in R) environment, an open source framework for the development and evaluation of management strategies. A reference set of 20 possible operating models is presented, four of which are examined further. Results are presented in detail for five potential management strategies tested on these four operating models. A suite of performance statistics for this stock are used to assess these management strategies. The results of this MSE exercise are evaluated in the context of the NAFO approach to fisheries management and the potential for further progress with regard to the application of MSE on this stock in general is considered.
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    A scientific alternative to moratoria for rebuilding depleted international tuna stocks
    (Wiley, 2015) Hillary, Richard M; Preece, Ann L; Davies, Campbell R; Kurota, Hiroyuki; Sakai, Osamu; Itoh, Tomoyuki; Parma, Ana M; Butterworth, Doug S; Ianelli, James; Branch, Trevor A
    There is considerable international concern and scientific debate about the current state and future of tuna stocks worldwide and the capacity of Regional Fisheries Management Organisations to manage the associated fisheries effectively. In some cases, this concern has extended to predictions of imminent collapse with minimal chances of recovery, even under a commercial catch moratorium. As a viable alternative to a full fishery closure, the Commission for the Conservation of Southern Bluefin Tuna (CCSBT) has adopted a scientifically tested, adaptive rebuilding strategy for the depleted southern bluefin tuna (Thunnus maccoyii) stock. The management procedure (MP) adopted involves a harvest control rule that fully specifies the total allowable catch as a function of key indicators of stock status, adjusting future harvest levels every three years so as to meet the rebuilding targets agreed by CCSBT. It was chosen from a subset of candidate MPs selected following extensive simulation testing. This involved first selecting a wide range of plausible scenarios for stock status and input data, ranging from pessimistic to optimistic, against which the alternative candidate MPs were tested to ensure that they were robust to important uncertainties. This is the first time that a comprehensively evaluated MP has been adopted for an internationally managed tuna stock. Both the process and the outcomes have broad applicability to other internationallymanaged stocks.