Geomorphic characterization of reef fish aggregation sites in the upper Florida keys, USA, using single-beam acoustics

The objective of this study was to determine if multiple reef fish aggregation sites in the upper Florida Keys share characteristic geomorphic features. A commercial single-beam acoustic seabed classification system was used to map the seabed in the vicinity of reported or observed black grouper (Mycteroperca bonaci), mutton snapper (Lutjanus analis), and yellowtail snapper (L. chrysurus) aggregation sites. Results showed that drowned, margin-parallel, rocky ridges, known locally as outlier reefs, were features found in proximity to all of the mapped aggregation sites. In particular, three geomorphic characteristics were observed at most sites: a steep slope of the landward boundary of the upper slope terrace, an exposed outlier reef forming the seaward boundary of the upper slope terrace, and at least one other exposed outlier reef on the upper slope terrace. The results suggest that the acoustic-mapping technologies used herein could be valuable when considering the placement of marine reserves.