An illustrative example of a management procedure for Eastern North Atlantic Bluefin tuna.
reportposted on 25.03.2022, 13:11 authored by Rebecca A Rademeyer, Doug ButterworthDoug Butterworth
This document provides an illustrative example of the development of Candidate Management Procedures (MPs) for the Eastern North Atlantic bluefin tuna resource. Its purpose is to draw attention to key components of this process, including the specification of a number of alternative Operating Models (OMs) which describe plausible dynamics for the resource, the choices of abundance indices for use for input to MPs and of the error structures associated with the generation of future data corresponding to those indices, and consideration of key performance statistics related to future catch levels and resource conservation to allow consideration of the different trade-offs between these for alternative MPs. The MPs examined use a combination of target and slope based approaches applied to simulated future abundance indices from Japanese longline operations and a larval survey in an area of the western Mediterranean. MP trials are carried out for four OMs which reflect alternative resource assessments and choices for relationships between recruitment and spawning biomass. The greatest challenge appears to come from a scenario with both high and low recruitment regimes when there is a change from the former to the latter. If catches are allowed to go high to benefit from the period of high recruitment, can the change in regime be identified sufficiently soon to allow for adequate catch limit reductions to ensure resource conservation during the later years of lower recruitments?