The Dependence of Biomass and Yield on Movement and Fishery Rates

Recent implementation of Marine Protected Areas (MPAs) along the California coast has provided the opportunity for monitoring and assessment of their effects, according to the principles of adaptive management.  That monitoring has begun, and early results will be reported in a presentation by Carr, et al. in this symposium.  Here we report on modeling studies to describe the short-term, transient responses that should be expected of populations responding to MPA implementation.  Earlier modeling studies – focused on long-term equilibrium conditions – indicated that changes in biomass and yield in the long term depended critically on the level of fishing outside MPAs, as well as larval dispersal distances and movement of juvenile and adult fish.  These same factors influence transient responses of populations within several years of MPA implementation.  We describe how the transient responses of populations with lower fishing rates, larger home ranges and longer larval dispersal distances will be more difficult to detect.  We place these in the context of results from monitoring thus far and in the future.