In the past decade, significant efforts have been made to describe fish-habitat associations. However, most studies have oversimplified actual connections between fish assemblages and their habitats by using univariate correlations. The purpose of this study was to identify the features of habitat forming corals that facilitate and influences assemblages of associated species such as fishes. For this we developed three-dimensional models of colonies of Acropora cervicornis to estimate geometry (length and height), structural complexity (i.e., volume, density of branches, etc.) and biological features of the colonies (i.e., live coral tissue, algae). We then correlated these colony characteristics with the associated fish assemblage using multivariate analyses. We found that geometry and complexity were better predictors of the structure of fish community, compared to other variables such as percentage of live coral tissue or algae. Combined, the geometry of each colony explained 40% of the variability of the fish assemblage structure associated with this coral species; 61% of the abundance and 69% of fish richness, respectively. Our study shows that three-dimensional reconstructions of discrete colonies of Acropora cervicornis provides a useful description of the colonial structural complexity and may explain a great deal of the variance in the structure of the associated coral reef fish community. This demonstration of the strongly trait-dependent ecosystem role of this threatened species has important implications for restoration and conservation efforts.

Eight years ago (2007), the distribution and status of Acropora palmata was quantified throughout Los Roques archipelago in Venezuela. The aim was to produce a baseline study for this species which combined population genetics with demographic data. The results highlighted that A. palmata had the potential to recover in at least 6 out of 10 sites surveyed. Recovery potential was assumed to be high at sites with a relatively high abundance of the coral, low disease prevalence, high genetic diversity, and high rates of sexual reproduction. However, as noted, Zubillaga et al. (2008) realized recovery was still strongly dependent on local and regional stressors. In 2014 (this study), the status of A. palmata was re-evaluated at Los Roques. We increased the number of sites from 10 in the original baseline study to 106. This allowed us to assess the population status throughout the entirety of the MPA. Furthermore, we also identified local threats that may have hindered population recovery. Here, we show that A. palmata now has a relatively restricted distribution throughout the park, only occurring in 15% of the sites surveyed. Large stands of old dead colonies were common throughout the archipelago; a result which demonstrates that this species has lost almost 50% of its original distribution over the past decades. The majority of corals recorded were large adults (∼2 m height), suggesting that these older colonies might be less susceptible or more resilient to local and global threats. However, 45% of these surviving colonies showed evidence of partial mortality and degradation of living tissues. Interestingly, the greatest increase in partial mortality occurred at sites with the lowest levels of protection (; df = 4, p < 0.05). This may suggest there is a positive role of small scale marine management in assisting reef recovery. We also recorded a significant reduction (; df = 8; p < 0.05) in the density of A. palmata in sites that had previously been categorized as having a high potential for recovery. One explanation for this continued decline may be due to the fact that over the past 10 years, two massive bleaching events have occurred throughout the Caribbean with records showing that Los Roques has experienced unprecedented declines in overall coral cover. We therefore conclude that although local protection could promote recovery, the impacts from global threats such as ocean warming may hamper the recovery of this threatened species.

Global and local stressors are causing the worldwide loss of coral cover and structural complexity at an unprecedented pace on reefs. In consequence, the habitat of coral reef fish has suffered a profound degradation affecting the abundance, biodiversity and species composition of this taxonomic group. Thus, understanding the link between coral reef fish assemblages and their habitats is paramount to predict their responses to increasing human threats. Herein, we implemented Structure from Motion (SfM) techniques and digital mosaics to characterize the habitat of reef fish in terms of structural complexity and cover of benthic organisms, and we examined the relationships between these metrics and the variation in fish assemblages among sites using a multivariate approach. We found that attribute of fish assemblage varied across reef sites in Los Roques, depending on the highly specific features of the benthic habitat. Results indicate that 69% of the variation in species-specific abundances of fish (i.e., reef fish assemblage structure) was explained by cover of massive coral and turf algae, the number and sizes of holes, and the site. Furthermore, when fish biomass per species was utilized as a response variable, 64% of the variation in assemblage structures was explained by a model that included: cover of crustose coralline algae (CCA), variation and the maximum height of reef structures along the transect, the number of holes and the site. All these variables together also explained >60% of variation of total abundance, biomass and species richness. When data were sorted by trophic groups, CCA cover explained 70% of the variation in forager biomass, whereas the number of holes explained up to 60% of variation in carnivore biomass. These results suggest that each trophic group relates differently to the benthic habitat. We conclude that variation in fish assemblages among sites can be explained by features of the benthic habitat, but more importantly the absence of specific attributes may impact fish trophic groups differently.

Adaptation to changes in the delivery of ecosystem services while maintaining resilience of natural systems is one of the main challenges faced by multi-use marine protected areas (MPAs). To overcome this, it is crucial to improve our understanding of interdependencies among resource users and ecosystems. In this study we used networks to model the socio-ecological system of a multi-use MPA in the southern Caribbean. Using a mixed-method approach, we built a socio ecological network (SEN) from the flow of economic benefits that stakeholders obtain from coral reefs in Los Roques National Park. We specifically looked at how these benefits are distributed among stakeholder groups and how the structure and other network properties can inform management. For this, four networks (simple, weighted, directed and directed-weighted) were built from 125 nodes representing three services and six stakeholder groups, linked through 475 edges. The SEN structure indicated an open resource use pattern with reduced social capital, suggesting that community-based management could be challenging. Only 31% of the benefits from ecosystem services stay within the SEN. Regulation services, derived from the coral reef framework were the most important in terms of maintaining the flow of benefits through the SEN; however, most benefits depended on provisioning services. This approach, based on network theory allowed identification of inequalities in the access to benefits among groups, externalities in benefits derived from fisheries and trade-offs between provisioning and regulation services. Our results suggest that Los Roques might be falling into a socio-ecological trap. Improving access to benefits and increasing trust need be prioritized. Low-cost management intervention can help internalize financial benefits and reduce trade-offs affecting more vulnerable stakeholder groups. However, these would require changes in governance and institutions at the executive level.