Several studies conducted at the scale of islands, or small sections of continental coastlines, have suggested that mangrove habitats serve to enhance fish abundances on coral reefs, mainly by providing nursery grounds for several species known to have different habitats as juveniles and adults. However, evidence of such enhancement at a regional scale has not been reported, and recently, some researchers have questioned the mangrove-reef subsidy effect. Authors of this paper used the REEF database to evaluate mangrove-reef connectivity at the Caribbean regional scale. They specifically asked: (1) Are reef fish abundances limited by mangrove forest area?; and (2) Are mean reef fish abundances proportional to mangrove forest area after taking human population density and latitude into account? They tested for Caribbean-wide mangrove forest area effects on the abundances of 12 reef fishes that have been previously characterized as “mangrove-dependent”. Results showed that average reef fish densities of at least six of the 12 focal fishes were directly proportional to mangrove forest area. This is the first scientific study to show that at a large regional scale (i.e., the Wider Caribbean), greater mangrove forest size generally functions to increase the densities on neighboring reefs of those fishes that use these shallow, vegetated habitats as nurseries.
This study is a great example of the power and impact that long-term, wide-spread citizen science programs such as the REEF Volunteer Fish Survey Project can have on addressing important ecological and management questions that would otherwise be near impossible to evaluate.