Reef assessment and spatial prioritization for validating the adequacy of a three-decades-old marine protected area zoning

Alacranes, the largest bank reef in the Gulf of Mexico, was decreed as a Marine Park in 1997, and its management program was published in 2006 based on field data collected during the early 1990s. The current global trend of coral reef degradation provides a strong rationale to reassess the ecological basis of legacy management frameworks. We evaluated the adequacy of the existing marine protected area zoning of Alacranes Reef using a spatial conservation prioritization approach. A robust stratified sampling design encompassing 111 sites across the reef platform was implemented, supported by high-resolution satellite imagery. At each site, surveys consisted of a 50 m2 benthic video transect and a 100 m2 visual fish census. Contemporary field data (benthic and fish communities, 2022; RapidEye imagery, 2017) were integrated with historical records (benthic and fish data, and Landsat 7 imagery from 1999 to 2000) to conduct a multi-criteria spatial conservation prioritization analysis, generating spatial layers of habitat change, habitat prioritization, patch complexity, habitat connectivity, and beta diversity. The environmental assessment indicated that coral structural habitats are currently in fair condition, while biomass of key commercial fish species was classified as very good, evidencing a marked recovery relative to records from 25 years ago. Cartographic analysis showed that the current total protection zone encompasses 58% of high-priority habitats, supporting the overall adequacy of the existing zoning; however, spatial prioritization identified three additional high-value areas outside current no-take boundaries, which could be added to the total protection zone when the management program is updated.