Status of the MSE work

• The reference operating model for the Indian Ocean swordfish stock was developed over the last three years and has been endorsed by the IOTC scientific committee. The OM was developed based on the 2020 WPB SS3 assessment, and covered the dynamics of the swordfish until the year 2018. This OM was updated to the current year, 2023, by projecting the stock forward based on the reported catches for 2019, 2020 and 2021 and assuming a 2022 catch at the 2021 level.
• The choices made in 2020 for the construction of the OM by the previous researcher have been revisited. following the feedback received during the 2022 working party on billfish (WBP20). The structural uncertainty grid (different options for the stock assessment model parameters) was simplified by removing those parameters that were found to have little impact on the assessment (e.g. choice of the scaling method for the CPUE indices). This change in the grid resulted in a reduced number of combinations to consider, but in the end in a higher number of valid stock assessment models that can serve as the basis for the OM.
• Further developments to the swordfish MSE included the development and application of two types of candidate MPs, one model-based and one data-based, and the tuning of these MPs (i.e. defining the MP parameters that achieve a certain management goal) for a range of management objectives over the next 11 to 15 years.
• An in-depth analysis of the impact of the choices of the parameters for the CPUE MP was conducted in order to make an informed choice of the value of those parameters that are not obtained by tuning. On the basis of this investigation, a configuration of the CPUE MP with low reactivity to the changes and values in the CPUE index used for management was proposed.