There is a need to understand the potential impacts on ecosystems and economies from shifting fisheries management towards individual transferable quota (ITQ) programmes. Multispecies fisheries present the challenge of understanding spatial patterns in fisher behaviour as they strive to balance profitable target catches while avoiding species with low catch limits. A spatially explicit model of biological and fleet dynamics was constructed to evaluate how the limited-entry groundfish trawl fleet off the US west coast and selected groundfish species (targeted Dover sole, and overfished darkblotched rockfish) were affected by two approaches to management: trip limits and ITQs. The model includes regional populations for both species, provides biological and socio-economic outputs, and determines quota price endogenously when applied for ITQs. Under ITQ management, effort and the total landings of the overfished species, darkblotched rockfish, were lower, coastwide profits higher, and the centre of fishing activity shifted south to areas with lower landing rates of darkblotched rockfish. The framework presented holds promise for obtaining insight about how new, untested management alternatives affect coastal and marine resources and those who rely on them.