Functional diversity of Cuban reef fish: implications of fishing intensity and regulation enforcement

Human pressures and climate change are transforming coral reef ecosystems, threatening both the biodiversity and the services they provide. These disturbances can reshape the functional composition of reef fish communities, weakening the ecological processes that support reef stability and resilience. Understanding these changes is essential for informing effective management and conservation. Here, we present findings from an expedition that surveyed 64 Cuban reefs along a 2000 nautical-mile route, examining variation in enforcement and fishing intensity. We hypothesized reef fish functional diversity declines where enforcement is weak and fishing pressure is high, predicting strong associations between diversity indices, enforcement strength, and fishing intensity. We quantified species biomass, defined functional traits using ten ordinal and nominal variables, and calculated functional alpha- and beta-diversity indices at each site. To analyze patterns in alpha and beta-diversity, we used linear models and multivariate statistics, respectively, with enforcement and fishing intensity as covariates. All alpha diversity indices, except functional evenness, increased with stronger enforcement and decreased with higher fishing intensity, indicating local fish communities responded strongly to management. Beta diversity analyses revealed significant differences in community composition across sites, also following gradients of stronger enforcement but, conversely, lower fishing intensity. Our results highlight clear trends: (1) unprotected sites showed predator depletion, while (2) well-protected sites supported higher biomass and larger mobile predators due to fishing exclusion. Together, these findings demonstrate the critical role of effective enforcement in maintaining reef fish functional diversity and protecting the ecological processes that support coral reef resilience.