Plausibility and uncertainty of basic data and parameter selection on stock assessments: A review of some input data used in the 2017 Assessment of the Shortfin Mako (Isurus oxyrinchus) of the northern Atlantic stock

Three key-elements for the case of shortfin mako used in 2017 assessment of North Atlantic stock are reviewed. The catch scenarios implemented indicate that historical T1 considered in base case scenario (C1) have greatly underestimated the level of catches during several of the initial decades, taking into consideration the history of the fisheries, fleet’s capacity and fishing effort by fleet. A hypothetical catch scenario also used (C2) probably overestimated in an important amount the catch levels of some fleets and fleets combined for the most recent period of that series. The review of CPUE series suggests that there may be qualitative and/or quantitative limitations in some of them which would likely affect some series being considered as indicators of abundance. Some key biological parameters considered in the assessment are also reviewed and discussed, such as the growth model implemented and the age of first reproduction of the females, within a context compared to other studies, preliminary estimations from tagging-recapture data and those parameters applied in other stock of the same specie, and in other species from the same family.