Short-term constant catch projections for the Atlantic bluefin stocks based on the reconditioned MSE Operating Models.

The reconditioned MSE Operating Models (OMs) for Atlantic bluefin are used to provide SSB trend estimates for the two stocks of origin under different constant catches for the west area for the next five years. The purpose is to complement results from refined and updated conventional assessment methods. The result for a west area TAC of 2,350t (i.e., unchanged from 2021) is a median (across the weighted OMs) increase in the western stock of 10.6% or 4.5% from 2022 to 2023, with a 21% or 31% probability of a decrease, depending on whether or not results from R3 OMs are included in the computations. The median for the eastern stock either increases or drops slightly, respectively. When the R3 OMs are excluded, and allowance is made for an east area TAC increase to 40,000t from 2023 onwards, an annual west area TAC of 3,000t would, in median terms, maintain increases in the abundance of the western SSB for the next five years. The advantages and disadvantages of this approach compared to the conventional area-based assessment methods are discussed briefly.