Abstract

The continental shelf of the northwestern Gulf of Mexico has many, widely scattered, high-relief, bathymetric features (or banks) that represent important naturally occurring aggregation areas for exploited fish species (especially snappers and groupers). While a few of these banks are protected and monitored as national marine sanctuaries (e.g., Flower Garden Banks), most are unprotected and poorly studied. Here, we present initial results of a study of one such bank, Sonnier Bank, where we are developing survey approaches with sidescan sonar, seismic devices, SCUBA, ROV (remotely operated vehicle), and fish traps. Sonnier Bank appears as a ring of topographic peaks, covering approximately 12.6 km 2 . At the shallowest depths (< 30 m) we have observed a diverse community of unexploited reef fishes associated with millepora coral and sponges. In this shallower environment, rock hind (Epinephelus adscensionis) were the dominant serranid. The deeper (45 to 60 m) bathymetric features of Sonnier Bank had the greatest numbers of exploited reef fish species. Sidescan and ROV surveys identified these areas as more gradually sloping with large pieces of rubble (1 to 4 m in diameter). Notable aggregations of vermilion snapper (Rhomboplites aurorubens), red snapper (Lutjanus campechanus), and gray snapper (L. griseus) were present, and yellowmouth grouper (Mycteroperca interstitialis) and graysby (Cephalopholis cruentata) were also observed. Our ongoing efforts include the calibration of a laser array for measuring distances with ROV video/images, and comparisons of fish counts and measurements between divers and the ROV. The development of approaches with ROV may be an effective way to quantify and monitor commercially important snappers and groupers in these deeper, structurally-complex habitats.

PDF Preview