Temporal persistence of Red Grouper holes and analysis of associated fish assemblages from towed camera data in the Steamboat Lumps Marine Protected Area.
The Red Grouper Epinephelus morio is an ecologically and economically important Gulf of Mexico reef fish species. The well-documented excavation behavior of this species generates several-meter-wide holes that serve as habitat in otherwise structureless areas. These mesohabitats are notably dense within the Steamboat Lumps (SL) Marine Protected Area (MPA) in the eastern Gulf of Mexico. Previous work in the SL-MPA used high-resolution multibeam bathymetry to analyze changes in hole density and structure (width, height, and slope) between 2006 and 2009. The present study utilizes additional multibeam data collected in 2017 to further these analyses. Overall, the density of holes within the SL-MPA continued to increase, but no definite trend in structural changes could be identified. Additionally, a towed camera was used to directly observe 95 holes, of which 63 had detectable reef fishes. Within the occupied holes, approximately 46% had a Red Grouper or other grouper species (Epinephelidae) present. The most frequently observed species within the occupied holes were invasive lionfish Pterois spp., which were present in 84% of the holes. The increasing density of Red Grouper holes in the SL-MPA indicates that the closure of the area may be resulting in a more robust local population of this species. However, quick colonization of the holes by lionfish has occurred, and additional studies are necessary to determine the impact of this on grouper and other native reef fish populations found within this type of uniquely created habitat.