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Based on simulation evaluations of candidate harvest control rules by Adam and Bentley (2013),
Bentley and Adam (2014a,b, 2015, 2016), reviewed and endorsed by the Working Party on
Tropical Tunas (WPTT), Working Party on Methods (WPM), and the Scientific Committee
(SC), the IOTC adopted Resolution 16/02 “On Harvest Control Rules for Skipjack in the IOTC
Area of Competence.” This described the harvest control rule (HCR) to be used for setting a
recommended catch for skipjack (SKJ) and stated that its first implementation will be based
upon the 2017 stock assessment agreed by the WPTT and then endorsed by SC. Implementation
of the HCR to give a recommended catch limit for 2018–2020 is described in IOTC (2017a). The
Resolution also requested a further review and possible modification of the HCR to be conducted
no later than 2021.
In 2018, the IOTC WPM noted that the SKJ HCR is not a fully specified Management Procedure
(MP), since the underlying data required and assessment methodology are not defined. Hence
the WPM suggested that the review and potential revision required under Resolution 16/02 be
conducted with the aim of determining a full MP for SKJ. This was noted by the SC in 2018 and
provides the motivation and basis for the current work.
An MP includes the assessment or estimation method on which the HCR is based, as well as
the data inputs and the HCR itself. Simulation evaluation requires an operating model (OM),
to describe dynamics of the resource and how it responds to harvesting, plus a computational
framework that will generate artificial observations, apply the MP to estimate a management
recommendation, and then simulate the implementation of that recommendation in a closed
loop forward projection. The current report describes initial developments of such a framework,
specifically implementing Stock Synthesis III as the OM. Closed loop simulation evaluations of
the current HCR are performed so as to demonstrate the framework’s functionality.
