Does MPA mean ‘Major Problem for Assessments’? Considering the consequences of place-based management systems John C. Field 1* , Andre ´ E. Punt 2 , Richard D. Methot 3 & Cynthia J. Thomson 1 1 Fisheries Ecology Division, Southwest Fisheries Science Center, NOAA Fisheries, 110 Shaffer Rd., Santa Cruz, CA 95062, USA; 2 School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98195-5020, USA; 3 Office of Science and Technology, NOAA Fisheries, 2725 Montlake Blvd. E, Seattle, WA 98112, USA Introduction 285 MPAs, stock assessments and spatial modelling in marine ecosystems 286 The role of fisheries science in management 287 Fishery-dependent information 288 Life-history information 290 Catch demographic data 291 Fishery-independent surveys 291 Spatial variability and movement patterns 293 Structure of assessment models 293 Fisheries management objectives and obligations 296 Abstract Marine protected areas (MPAs) have been increasingly proposed, evaluated and implemented as management tools for achieving both fisheries and conservation objectives in aquatic ecosystems. However, there is a challenge associated with the application of MPAs in marine resource management with respect to the consequences to traditional systems of monitoring and managing fisheries resources. The place-based paradigm of MPAs can complicate the population-based paradigm of most fisheries stock assessments. In this review, we identify the potential complica- tions that could result from both existing and future MPAs to the science and management systems currently in place for meeting conventional fisheries manage- ment objectives. The intent is not to evaluate the effects of implementing MPAs on fisheries yields, or even to consider the extent to which MPAs may achieve conservation oriented objectives, but rather to evaluate the consequences of MPA implementation on the ability to monitor and assess fishery resources consistent with existing methods and legislative mandates. Although examples are drawn primarily from groundfish fisheries on the West Coast of the USA, the lessons are broadly applicable to management systems worldwide, particularly those in which there exists the institutional infrastructure for managing resources based on quantitative assessments of resource status and productivity. Keywords fisheries assessment, fisheries management, fish stock, marine protected area, spatial model *Correspondence: John C. Field, Fisher- ies Ecology Division, Southwest Fisheries Science Center, NOAA Fisheries, 110 Shaffer Rd., Santa Cruz, CA 95062, USA Tel.: +1-831-420- 3907 Fax: +1-831-420- 3977 E-mail: john.field@ noaa.gov Received 26 May 2006 Accepted 15 Aug 2006 284 Ó 2006 Blackwell Publishing Ltd F I S H and F I S H E R I E S , 2006, 7, 284–302