Abstract
In South Florida and the Caribbean, fish populations have experienced significant declines due to overfishing, habitat degradation, and rising ocean temperatures (Lirman et al., 2019). Marine protected areas have proven effective in conserving marine ecosystems, often resulting in increased fish biomass, density, and occurrence (Marcos et al., 2021). Since 2002, the South Florida/Caribbean Monitoring Network of the National Park Service (NPS) has conducted long-term monitoring and inventory of fish communities within national parks in the region, encompassing many fished and protected areas. Dry Tortugas National Park, located approximately 110 km west of Key West, encompasses extensive coral reef systems and is a critical site for marine conservation (Herbig et al., 2024). In 2007, the Research Natural Area (RNA) was established within the park as a no-take zone, protecting natural resources while allowing for ongoing scientific research (Ault et al., 2013). With nearly two decades of monitoring data available, this project used long-term Reef Visual Census (RVC) survey data to assess how no-take management influences reef fish community structure by comparing fish density, occurrence, and size across protected and fished areas. Temporal trends in fish populations inside and outside the RNA were evaluated under the hypothesis that fish populations would increase across all zones from pre-RNA baseline levels, with consistently higher metrics inside the RNA reflecting both direct protection and potential spillover effects. Results indicate that responses to protection were species-specific. Yellowtail snapper and mutton snapper exhibited strong positive responses, whereas other species, such as black grouper, showed limited recovery or continued declines. Overall, fish density, occurrence, and size were generally higher inside the RNA than in fished areas, highlighting the effectiveness of no-take protection. These patterns underscore the role of species-specific life-history traits in shaping responses to management and demonstrate the value of long-term monitoring for evaluating marine reserve performance and broader ecological benefits in the region.