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To forecast resource and fishery responses to artificial reefs deployed within no-take marine protected areas, we discuss an application of E cospace , a policy evaluation tool based on spatially explicit simulation of ecosystem dynamics. We analyse a recent initiative to establish human-made reefs inside Marine Special Areas in Hong Kong. Simulations commence with a static mass-balanced model of trophic flows among he functional groups of an ecosystem (E copath ), which is then used to structure dynamic simulations of the biomass fluxes in response to fishing (E cosim ). Spatial modelling is achieved through definition of dispersion, foraging, and predator avoidance parameters for each group in relation to a range of defined habitats (E cospace ). The ecosystem model comprised 27 functional groups and 7 sectors of the Hong Kong fishery, which were assumed to increase their catching power by 3% year −1 . Seven fishery sectors and gear types are defined, and their operations are simulated spatially to maximize operating profit within the areas where they are allowed to fish. Parameters for E copath , E cosim , fishery, and habitats were obtained from recent surveys and assessments. Additional parameter values were obtained from meta-analyses and other literature on fishes of the South China Sea. More than 250 fish species were assigned to reef-associated and non-reef-associated functional groups with the help of an expert consultation. Results express average spatial responses to fishing and protected reefs. First, E cospace was used to evaluate biomass responses and catch returns from a range of artificial reefs/marine protected area complexes in which size, perimeter, and corridor design were varied according to biogeographical theory. Benefits that might be deliberately forgone to obtain the cooperation of fishers by allowing them to fish designated reefs were also estimated. Secondly, five specific policy scenarios were evaluated using a spatial map of Hong Kong waters. Gains and losses to different fishery sectors were tracked, along with shifts in the species composition of the catches. While small protected areas with human-made reefs achieve little to avert collapse of the fisheries or a shift towards catches of low-value species, larger protected areas can do much to restore valuable fisheries for reef-associated fish. Precise results, but not the overall patterns, are sensitive to uncertainties in many model parameters. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved .