Spatial ecology of Nassau Grouper at home reef sites: using acoustic telemetry to track a large, long-lived epinephelid across multiple years (2005-2008)

Characterizing the behavior of coral reef fishes at home reef sites can provide insight into the mechanisms of spatial ecology and provide a framework for spatial resource management. In the Caribbean, populations of Nassau grouper Epinephelus striatus have declined due to fishing impacts on spawning aggregations. Despite local and regional efforts by fisheries managers to implement regulations protecting spawning aggregations, few Nassau grouper populations appear to be recovering. In order to improve management strategies for this critically endangered species, it is necessary to understand the spatial ecology of the species across seasons and years. In the Cayman Islands, we used a multi-year, presence/absence, depth-coded acoustic tagging dataset of Nassau grouper to characterize patterns in the species’ behavior and vertical habitat use at home reef sites. Twenty acoustically tagged individuals (56-84 cm, 70.01 ± 7.40 cm; total length, mean ± SD) maintained consistent home reef sites, although some fish regularly shifted activity centers within the home site, often following a seasonal spawning migration. Seven fish with depth-coded tags showed a higher probability of vertical movement in the hours immediately following dawn and preceding dusk. We found evidence of a positive relationship between the fish condition factor and depth of home reef site. The finding of persistent home reef sites across years suggests that properly sized spatial reserves at home reef sites can be a useful complement to spawning aggregation protection when considering management strategies for Nassau grouper.