69 Abstract—Submersible surveys at nu- Deep reef fish surveys by submersible on merous reefs and banks in the north- western Gulf of Mexico (NWGOM) were Alderdice, McGrail, and Sonnier Banks in conducted as part of the Sustainable Seas Expedition (SSE) during July/August the Northwestern Gulf of Mexico 2002 to identify reef fish communities, characterize benthic habitats, and iden- Douglas C. Weaver tify deep coral reef ecosystems. To iden- tify the spatial extent of hard bottom reef Emma L. Hickerson communities, the Flower Garden Banks George P. Schmahl National Marine Sanctuary (FGBNMS) Flower Garden Banks National Marine Sanctuary, NOAA and the U.S. Geological Survey (USGS) 4700 Avenue U, Building 216 mapped approximately 2000 km2 of the Galveston, TX 77551 Northwestern Gulf of Mexico (NWGOM) Email (for Weaver): [email protected] continental shelf during June 2002 with high-resolution multibeam bathymetry. Previous investigations conducted on the features of interest (with the exceptions of East and West Flower Garden and Son- nier Banks, accessible by SCUBA) had Introduction The reefs and banks of the north- not been conducted since the 1970s and western Gulf have been afforded some 1980s, and did not have the use of high- resolution maps to target survey sites. The The northwestern Gulf of Mexico protection since the early 1970s. The base maps were instrumental in navigating (NWGOM) reefs and banks are asso- MMS recognized early on that these submersibles to specific features at each ciated with the surface expression of sensitive areas should not be subjected study site during the Sustainable Seas salt domes, and have been identified to the direct impacts of offshore oil and Expedition (SSE)—a submersible effort as unique biological features warrant- gas development, and defined them as culminating from a partnership between the National Atmospheric and Oceanic ing protection by Minerals Manage- “no activity” zones (Fig. 1). However, Administration (NOAA) and the National ment Service (MMS) from oil and gas these features are subject to a variety Geographic Society (NGS). We report the activities. The most recent investiga- of other potential impacts unrelat- initial findings of our submersible surveys, tions of reef fishes on the shelf-edge ed to offshore development, which including habitat and reef fish diversity at features in the northwestern Gulf may not be regulated sufficiently. McGrail, Alderdice, and Sonnier Banks. A total of 120 species and 40,724 indi- (with the exceptions of East and West These impacts include those of com- viduals were identified from video surveys Flower Garden, Stetson and Sonnier mercial shipping (predominantly an- at the three banks. Planktivorous fishes Banks) were conducted during the choring), fishing, cultural resource constituted over 87% by number for the 1970s and 1980s (Rezak et al., 1985; recovery and recreational activities. three banks, ranging from 81.4% at Son- Dennis and Bright, 1988a, 1988b), There is recent emphasis on the in- nier Banks to 94.3% at Alderdice Bank, indicating a direct link to pelagic prey without the use of high-resolution creased use of marine protected areas communities, particularly in the deep multibeam bathymetry or high-resolu- (MPA’s) in many ocean regions as a reef zones. High numbers of groupers, tion camera systems. method to consolidate management snappers, jacks, and other fishery spe- The Sustainable Seas Expedition under a coordinated mechanism. Ac- cies were observed on all three features. (SSE) was a five-year collaborative curately identifying the resources in These sites were nominated as Habitat Areas of Particular Concern (HAPC) by effort between NOAA and the Na- the northwestern Gulf will contribute the Gulf of Mexico Fishery Council in tional Geographic Society (NGS) to greatly to this effort. March 2004. Data obtained during this explore important marine ecosystems project will contribute to benthic habitat with special emphasis on the nation’s characterization and assessment of the as- National Marine Sanctuaries. Led by Background sociated fish communities through future SCUBA, ROV, and submersible missions, Sylvia Earle, Explorer-in-Residence of and allow comparisons to other deep reef the NGS, the SSE program utilized The Department of Oceanography ecosystems found throughout the Gulf of both manned and unmanned sub- at Texas A&M University (TAMU) Mexico and western Atlantic Ocean. mersible technologies to explore the conducted studies on “topographic NWGOM in 1999, 2001, and 2002. features”—Outer Continental Shelf The use of the submersibles allowed (OCS) reefs and banks—during the the Flower Garden Banks National 1970s and 1980s. Funding was pro- Marine Sanctuary (FGBNMS) team vided by the U.S. Department of the to visit several of the reefs and banks Interior (DOI), Bureau of Land Man- of the NWGOM and conduct explor- agement (BLM), out of which MMS atory dives to investigate reef fish and later emerged through reorganiza- benthic communities in July 2002. tion. The purpose of the TAMU study 70 Professional Paper NMFS 5 Figure 1 Location of outer shelf banks in the northwestern Gulf of Mexico. was to provide the MMS with data on the geologic, sandstone outcrops on the crests of these features. The biologic, hydrologic, and chemical characteristics of the Algal-Sponge Zone covers the largest area among the reefs and banks, to be used as a basis for management reef-building zones on shelf-edge banks. The dominant decisions on tracts nominated for oil and gas leasing organisms of the zone are the coralline algae, which (Rezak et al., 1985). are the most important carbonate producers through As a comparison, the technology used for the his- algal nodules and algal reefs (Minnery et al., 1985). The toric surveys conducted by Rezak et al. (1985) included nodules range from 1 to 20 cm in size, cover up to 80 bathymetric mapping using a LORAN-C positioning sys- percent of the bottom, and generally occur between 55 tem for navigation, a 3.5kHz subbottom profiler, EG&G and 85 m. Partly Drowned Reefs are also a major biotope Uniboom seismic system for subbottom information, occurring at similar depths to the Algal-Sponge Zone, and EG&G side-scan sonar systems for bottom char- and are defined as massive reefal structures covered with acterization. Direct observations of the sea floor were living crusts of coralline algae. With increased water made using the Texas A&M submersible DRV Diaphus depth, the assemblages of the zone become less diverse, (Rezak and Tieh, 1984; Dennis and Bright, 1988a). characterized by antipatharians, comatulid crinoids, di- Each of the survey sites has a distinct biological zona- minished leafy or coralline algae, and limited fish. High tion associated with base depths and water turbidity, turbidity, sedimentation, and re-suspension occur in the and the following zones (when present), described dur- Nepheloid Zone, where exposed rocks lack encrusting ing the early TAMU/MMS studies (Rezak et al., 1985; coralline algal crusts. Drowned Reefs occurring in this 1990). The Stephanocoenia-Millepora Zone is inhabited zone are often covered with a thin veneer of sediment, by a low-diversity coral assemblage of 12 hermatypic and epifauna are scarce. This zone occurs on all banks, coral species and can be found at the FGBNMS, Mc- but its depth differs at each bank and extends to the Grail Bank, and Bright Bank to depths of 50 m. On surrounding soft bottom. midshelf banks, such as Stetson and Sonnier Banks, the The Sonnier Bank complex (historically referred Millepora-Sponge Zone occupies depths less than 36 m. to as Three Hickey Rock and Candy Mountain) is a Crusts of the hydrozoan coral, Millepora, sponges, and mid-shelf bank, defined by Rezak et al. (1985, 1990) as other epifauna occupy the tops of siltstone, claystone, or salt dome structures rising from depths of 80 m or less Weaver et al: Reef fish surveys by submersible in the Northwestern Gulf of Mexico 71 and having a relief of about 4 to 50 m. The banks are northwestern Gulf of Mexico continental shelf1. Multi- located 135 km south of the Louisiana border, at posi- beam bathymetry data sets were used as base maps to tion 28°20ʹN/92°27ʹW. As noted by Rezak et al. (1985) guide submersible surveys of select topographic features the Sonnier Bank complex consists of eight separate during the 2002 Sustainable Seas Expedition to the banks or peaks associated with a single salt dome. The northern Gulf of Mexico, conducted by the FGBNMS peaks are nearly conical features with a maximum re- in conjunction with the NGS. lief of about 30 m. Observations made by SCUBA and The SSE missions initiated an ongoing multidisci- submersible have characterized the reef habitat on the plinary project led by the FGBNMS to revisit the reefs peaks as entirely encrusted with fire coral (Millepora and banks of the NWGOM and build on the descrip- sp.) and sponges (primarily Neofibularia nolitangere and tion and characterization effort conducted during past Ircinia sp.) (Rezak et al., 1985). This is the basis for the research programs. zonation name of Millepora-Sponge Zone. Rezak et al. During the SSE missions, submersible dives were con- (1985) reported three species of coral from the crests ducted on the East Flower Garden (EFGB), West Flower at Sonnier Banks: Stephanocoenia sp., Millepora sp., and Garden (WFGB), Jakkula, Sidner, Alderdice, Bright, Agaricia sp. In 1997, SCUBA surveys conducted by MMS McGrail, and Sonnier Banks. Results from the SSE and FGBNMS representatives compiled coral observa- submersible surveys at Alderdice, McGrail, and Sonnier tions on the two shallowest peaks (24 m and 18 m) of Banks are reported herein, due to the more extensive Sonnier Banks. Other hermatypic coral species added surveys conducted at these features. by MMS diver surveys include Madracis decactis, M. mirabilis, M. pharensis, Siderastrea radians, Montastraea cavernosa, and Agaricia fragilis.