Re-considering the appropriate risk level for anchovy in OMP-13 development

De Moor, Carryn L; Butterworth, Doug S

Re-considering the appropriate risk level for anchovy in OMP-13 development

Working Paper

2013

Publisher

University of Cape Town

Publisher

University of Cape Town

Department

Marine Resource Assessment and Management Group

Faculty

Faculty of Science

Abstract

The acceptable level of risk changes from one MP to the next given changes in the perceived level of productivity of a resource resulting from the inclusion of revised and new data in the underlying operating models. This is because the more or less the abundance of an unexploited resource fluctuates naturally (see, for example, the biomass distributions in the absence of catches that are implied by different operating models which are shown in Figure A.1), the more or less resilient it is likely to be to reduction to a specified level through exploitation, and hence the greater or lesser the acceptable probability that fishing reduce the resource to below that level. de Moor and Butterworth (2010) developed an objective method for determining an acceptable level of risk for a new MP that maintained comparability with that adopted in selecting the previous MP. This method was applied to obtain a revised level of risk for sardine in developing Interim OMP-13 (de Moor and Butterworth 2012b). However, the application of this method to obtain a revised level of risk for anchovy for Interim OMP-13 was not straightforward given changes (supported by analyses of updated time series of data) in the selected natural mortality values and stock-recruitment relationships from the operating model used to develop OMP-08 (de Moor and Butterworth 2012a).

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