Indian Ocean Tellowfin Tuna SS3 Model projections

This document presents the projections and Kobe II Strategy Matrix (K2SM) for the 2021 Indian Ocean yellowfin Stock Synthesis assessment model. Deterministic projections for 2021-2030 were conducted for the 96 reference grid scenarios assuming a constant level of catch at 60%-120% of the 2020 catch. The projections incorporate the range of uncertainty among alternative model structures but do not describe uncertainty due to parameter estimation error or stochastic future recruitment variability.
The present projections incorporate an explicit recruitment bias adjustment to avoid the likely overly optimistic results as identified by the Working Party on Tropical Tunas during the 23rd WPTT Stock Assessment meeting (WPTT, 2021, paragraph 125), if no explicit bias adjustment controls are used in the forecast. Also, as requested at the WPTT 23rd Stock Assessment meeting, we examine a reference model with and without bias correction to see how different the output projections are. It is important to note the importance of adjusting bias correctly