Description of the co-viability framework.
Two sets of constraints define the viability of the fishery:
- the first set of constraints relates to the population viability of the three species
- the second set of constraints relates to the economic viability of each individual sub-fleet.
Population Viability is defined as the requirement that the Spawning Stock Biomass of each individual species is maintained above a threshold value. . The constraint is specified as:The Economic Viability constraint consists in maintaining positive profits for the sub-fleets over time :
Co-Viability Analysis (CVA) of the fishery seeks to assess whether a management strategy allows for both sets of constraints to be observed simultaneously. The ecological and economic viability constraints characterize an acceptable sub-region of the phase space within which the fishery evolves. A particular trajectory followed by the fishery will be called viable if it remains in this region during the prescribed period of time, with a sufficiently high probability.
Management strategies rely on different combinations of effort multipliers uf. Projections are computed over twenty years (T = 2028) starting from the initial stock abundances Ns,a(t0) at year t0 = 2008.