Conditioning an operating model for Indian Ocean albacore

This document presents the process of conditioning and the current state of the Operating Model (OM) for
Indian Ocean albacore. The OM is being used for the initial evaluation of Management Procedures for the
stock following the guidelines providing by recent meetings of the TCMP (IOTC 2021b). The OM is based on
a grid of alternative runs based on the stock assessment for albacore (Langley 2019) carried out and accepted
by WPTmT in 2019.
Three system characteristics of the Operating Model and the Observation Error Model are likely to have the
greatest inuence in the performance of an MP: scale, noise and trend. The strategy for development of an
MP described here tries to ensure that a realistic range of options for those three quantities are present in the
OM set.
Model runs have been selected based on four criteria related to their t to the data, prediction skill, and ability
to explain recent catches. A large proportion of model runs did not pass these tests. Finally, the remaining
runs were resampled using sampling weights based on their prediction skill for the two CPUE indices to be
used in future projections.