Initial robustness trial of empirical MPs for Indian Ocean skipjack tuna

The objective of this work is to develop a Management Procedure (MP) for Indian Ocean
Skipjack tuna (SKJ), which includes specification of the data inputs, harvest control rule (HCR)
and management outputs, and that has been fully tested using an appropriate simulation
framework.
A simulation framework has been proposed to the Working Party on Methods (WPM; Edwards,
2020, IOTC, 2020a) and the Technical Committee on Management Procedures (TCMP;
Edwards, 2021b, IOTC, 2021c), and evaluations of an empirical MP were delivered to the
WPM (Edwards, 2021a), and the MSE Task Force (Edwards, 2022a). At the TCMP in 2022, a
preliminary set of MPs was presented (Edwards, 2022b) and received feedback from the TCMP
(IOTC, 2022b). In particular:
67. The TCMP NOTED that previously, a request had been made to the
developer to remove positive bias in catches and therefore implementation
error had been removed from the OM tuning. The TCMP AGREED that it
is best practice to include implementation error and this option should once
again be explored in the tuning. In addition, the tuning should continue to
use the three options for being in the green zone of 50%, 60% and 70%.
In response, candidate MPs were tuned to the 50%, 60% and 70% turning criteria under the
assumption of constant, positive implementation error values of 10%, 20%, 30% and 40%.
These results were presented by Edwards (2022c) to the WPM (IOTC, 2022a). The current
work is a first step towards testing robustness of these candidate MPs to recruitment failure,
and ability of the MPs to recover the fishery.