Assessment of Commercially Important and Herbivorous Fish Species Ten Years After the Akumal Fishery Refuge Zone Decree

Abstract

Fishing Refuge Zones (FRZs) are intended to promote the recovery of exploited populations, but their ecological outcomes can be difficult to interpret on reefs where fisheries protection coincides with persistent habitat degradation, multiple local pressures, and limited implementation or continuity of management. We compared reef-fish assemblages and benthic condition at 23 repeatedly sampled stations within the Akumal Fishery Refuge Zone in 2015 and 2025. Fish biomass, abundance, and richness were evaluated for commercially important fishes, herbivores, and other reef fishes across shallow and deep fore-reef zones, together with differences in benthic cover and coral assemblages. These metrics were analyzed using generalized linear mixed models (GLMMs); exploratory redundancy analyses (RDAs) were additionally used to examine fish–benthic associations, and kernel density estimation (KDE) curves were used to describe size distributions. Total fish biomass was higher in 2025 when both reef zones were considered together, although this pattern varied spatially and was not accompanied by consistent differences in abundance or species richness. Commercially important fishes showed particularly low biomass in the deep fore reef in 2025 (238 to 31 g·100 m−2) and remained below the Healthy Reefs critical biomass threshold when both reef zones were considered together. In contrast, herbivore biomass was higher in 2025 (1578 to 2453 g·100 m−2), whereas abundance was 24% lower and species richness decreased from 5.7 to 4.7 species per transect. Concurrently, model-estimated hard-coral cover decreased from 10.5% to 5.5%, while macroalgal cover increased from 37.2% to 50.7%. Overall, these results provide no evidence of a generalized ecological recovery within the Akumal FRZ and highlight the importance of maintaining long-term monitoring programs that jointly integrate reef-fish communities and habitat condition.