Methods for Estimating Discards of Shortfin Mako (isurus Oxyrinchus) by the Portuguese Longline Fleet in the North Atlantic

This document presents preliminary information to start addressing the ICCAT Commission request for estimation of discards of shortfin mako (Isurus oxyrinchus) (ICCAT Rec 21-09), with a view to eventually allow for a possible future retention allowance in the North Atlantic. The intent of this paper is to provide an example of a possible approach for estimation of discards of shortfin mako in the Portuguese pelagic longline fleet, with known effort data, including date and location. The estimation is based on GAM models that modelled both total catches and discards of shortfin mako from fishery observer data between 2019 and 2022. With those models, and as an example, we then provide predictions for the dead discards and live releases in years 2020 and 2021.