Abstract

Before-after-control-impact (BACI) statistical approaches have been seldom applied to document spatio-temporal changes in no-take marine protected areas (MPAs) effectiveness. BACI approaches have been applied to detect environmental impacts in spite of the fact that the same basic principle of detecting impacts applies when analyzing management responses. In this study we applied a BACI approach to fish community long-term monitoring data from the Luis Peña Channel No-Take Natural Reserve, Culebra Island, Puerto Rico. The reserve was established in 1999. Data was collected using stationary visual censuses from a core zone site (Carlos Rosario Beach), a boundary zone site (Punta Melones), and from an outside control site (Punta Soldado). Data was averaged by depth zone (<5 m, 5 - 15 m) and comparisons were conducted among sites. The statistic of interest is called the Effect Size= ?CIB. – ?CIA, where ?CIB. is the “delta” or the change in the mean value of any given parameter in a control site when compared to an impacted site Before, and ?CIB. is the “delta” in the mean value of any given parameter in a control site when compared to an impacted site After. Effect size was calculated for fish species richness, abundance, total biomass, and biomass of total herbivores, scrapers, total carnivores, piscivores, and target fishery species. Calculations were independently made for both depth zones at each site to test for BACI effects. Results suggest that effect size was highly positive in the reserve core zone for all of the above parameters, particularly between 1999 and 2002. Reserve’s core zone showed a dramatic positive effect of fish recovery during the first three years following no-take designation when compared to boundary and control sites. Also, the boundary site showed a dramatic negative effect when compared to the core and control zones, suggesting a fish community collapse. Punta Melones has suffered the increasing effects of severe runoff pulses and possibly increasing fishing pressure from recreational fishers displacement from the reserve. Data from the core zone following year 2002 showed a declining trend in the effect size statistic for most parameters, suggesting illegal fishing effects. There was also a similar trend for many of the fishery target species. Effect size statistic can be a useful tool that can be applied to adaptive management strategies of no-take MPAs and should be incorporated into regular monitoring efforts.

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