A prevalent problem in shared fisheries is competition between commercial and recreational fishers for access to a resource that is subject to increasing utilisation pressure. For most shared fisheries in New Zealand, the commercial sector is efficiently managed with a regime of individual transferable quota (ITQ), but the recreational fishing is only minimally managed. A model is developed that can be used to explore the size of the total allowable catch (TAC) that is both sustainable AND maximises the value to the NZ economy of the combined commercial and recreational catch when the commercial catch is regulated via a total allowable commercial catch (TACC) while the recreational catch (RC) is self regulating. Determinants of the optimal catch allocation include: • the relative size of annual value to recreational fishers vis-à-vis the value of one unit of ACE to the commercial fishing sector from a unit decrease in the TACC • the relation between value to recreational fishers and size of stock biomass • the biology, and in particular the population dynamics of the fishery • the nature of the functional relationship between the self regulating recreational catch and stock biomass. The model can be applied to a fishery of interest by quantifying the above variables and relationships.