Marine Protected Areas (MPAs) are designed to conserve and preserve the ecosystems and cultural resources of the ocean. In theory, protected populations flourish, replenish adjacent regions, and are self-sustaining. However, describing the efficacy of MPAs requires long-term monitoring. Queen conch Lobatus gigas are iconic Caribbean denizens with populations that have been decimated by overfishing and are slow to rebound due to density-dependent breeding. The Exuma Cays Land and Sea Park (ECLSP) is a well-enforced, no-take, old, and large MPA. Surveys in 1994, 2011, and 2016 were used to track changes in the abundance, size, and age structure of conch within the park. Statistical models suggested that abundances of adults in 50 km of repeated towed-observer surveys had declined by 71% in 2016 relative to 2011. Further, the remaining conch populations were associated with tidal channels, and these model results agreed with independent observations in 40 km of expanded survey area. Measurements of shell lip thickness, an estimator of relative age, showed an increase relative to 1994 with the greatest effect in 2016, indicating senescence. The ECLSP population appears to be slowly dying of old age, and an early life history process has been altered. Upstream populations have been heavily fished while habitats within the park remain productive, suggesting that low local retention and a lack of exogenous larval sources are driving the decline. A network of MPAs encompassing the entire life cycle and dispersal envelope of targeted organisms is needed for proper conch conservation. Surveys focused on tidal channels could locate candidate upstream populations of conch.

Quantifying successful ecological spillover from marine protected areas (MPAs) is challenging yet crucial for conservation planning. The queen conch (Lobatus gigas) supports an iconic Bahamian fishery, but populations are declining. Here we provide evidence for MPAs as a solution: showing that a well-enforced MPA supplies ecological spillover through larval supply. Dive surveys throughout the Exuma Cays, including a centrally-located MPA, provided information on abundance, size, and age. Data showed higher-adult abundance within the MPA and positive associations between enforcement and conch size and age. A biophysical model estimated that MPA larvae settled in unprotected areas, and that MPA larval sources included unprotected sites with densities too low for reproduction. The MPA is currently sustaining nearby populations, yet its future is in jeopardy without upstream larval sources. Our results and consultations with stakeholders regarding management of the Bahamian conch fishery support creating a network of MPAs that exchange larvae for a sustainable future.

Establishing marine reserves can increase biomass and diversity relative to surrounding areas. However, such changes presumably alter species compositions, interactions, and associated demographic processes such as predation. We investigated relative predation pressure by fish inside and outside of a well-established no-take reserve using standardized predation tether units: Squidpops. We deployed Squidpops (N = 990) monitored by cameras to examine predation, as estimated by consumption rates, between paired seagrass and patch reef habitat sites proximate to the Exuma Cays Land and Sea Park, a well-enforced no-take Bahamian reserve since 1986. Surprisingly, there was no significant park effect on consumption nor observed diversity. Significantly higher consumption rates were found at patch reef sites relative to seagrass sites, occurred in association with higher fish diversity and with longer soak times. Observed fish diversity was predicted by habitat and distance inshore with more species found on patch reefs and further from the deep water Exuma Sound. Recorded fish bites were positively associated with patch reef habitat, with reef dwelling fish, and increased as the species became more commonly encountered. Deployment-specific factors, including temperature, depth, and time of day had little impact on measured predation, an expected result as the experiments occurred in similar locations over a fine temporal scale. In our experiment, ecosystem-based factors outweighed the place-based management effects that we expected from being within the oldest well-enforced no-take marine reserve in the Caribbean versus the surrounding actively fished waters. Despite well-documented increases in abundances across trophic levels from primary consumers to apex predators within the reserve, predation rates were not significantly different than adjacent areas. Evaluating the efficacy of a marine reserve in protecting vital ecosystem processes requires studies beyond abundance and diversity surveys. By focusing on predation on two of the most ubiquitous habitats throughout the region and on common species, rather than on exceptional sites and charismatic species, we reveal a process that seems relatively unchanged by strict marine conservation management.