A methodology that endogenously determines catchability functions that link fi shing mortality with
contemporaneous stock abundance is presented. We consider a stochastic age-structured model for
a fishery composed by a number of fi shing units (fleets, vessels or métiers) that optimally select
the level of fishing effort to be applied considering total mortalities as given. The introduction of
a balance constrain which guarantees that total mortality is equal to the sum of individual fi shing
mortalities optimally selected, enables total fishing mortality to be determined as a combination
of contemporaneous abundance and stochastic processes affecting the fishery. In this way, future
abundance can be projected as a dynamic system that depends on contemporaneous abundance.
The model is generic and can be applied to several issues of fisheries management. In particular, we
illustrate how to apply the methodology to assess the floating band target management regime for
controlling fishing mortalities which is inspired in the new multi-annual plans. Our results support
this management regime for the Mediterranean demersal fishery in Northern Spain.This work was funded by the European Commission as part of the MINOUW project (H2020-SFS-2014-2, number 634495) and the Spanish Ministry of Economy, Industry and Competitiveness (ECO2016-78819-R, AEI/FEDER, UE
