Abstract. — Reef fish communi- 

 ties at Gray's Reef National Marine 

 Sanctuary, Georgia, differed over 

 five different habitat types. Num- 

 bers of species and overall densi- 

 ties were highest on ledge habitat, 

 intermediate on live-bottom (three 

 categories of low relief [<15 cm] 

 rock outcroppings covered by algae 

 and macrofauna), and lowest over 

 sand. On average, abundance over 

 ledges exceeded that over sand bot- 

 toms by a factor of 50. Generally, 

 community composition at sites 

 over ledges and dense live-bottom 

 areas was similar and distinct from 

 sites found over sparse live-bottom 

 and sand. Many species were found 

 in more than one habitat and few 

 individual species could be consid- 

 ered indicators of a single habitat 

 type. A nondestructive, repeatable 

 procedure of randomly dispersed 

 video transects was devised for as- 

 sessing diurnally active fishes. 



A video transect method for 

 estimating reef fish abundance, 

 composition, and habitat utilization 

 at Gray's Reef National 

 Marine Sanctuary, Georgia 



Richard O. Parker Jr. 

 Alexander J. Chester 

 Russell S. Nelson 



Beaufort Laboratory, Southeast Fisheries Science Center 



National Marine Fisheries Service, NOAA 



Beaufort Laboratory, Beaufort, North Carolina 28516-9722 



Manuscript accepted 22 February 1994. 

 Fishery Bulletin 92:787-799. 



The geographic and depth distribu- 

 tion of fishes associated with reefs or 

 hard bottom off the southeastern U.S. 

 coast is generally known (Struhsaker, 

 1969; Huntsman and Manooch, 1978; 

 Miller and Richards, 1980; Powles 

 and Barans, 1980; Wenner, 1983; 

 Chester et al., 1984; Sedberry and 

 Van Dolah, 1984; Parker and Ross, 

 1986). Most of these studies have 

 demonstrated changes in commu- 

 nity structure associated with dif- 

 ferent depths and water tempera- 

 tures. Although trawl collections 

 over sand have been compared with 

 collections over hard bottom 

 (Wenner, 1983; Sedberry and Van 

 Dolah, 1984), no quantitative in situ 

 studies of the distribution of reef 

 fishes by type of substrate have 

 been published. 



Gray's Reef National Marine 

 Sanctuary (GRNMS), Georgia, one 

 of 14 Marine Sanctuaries managed 

 by the National Oceanic and Atmo- 

 spheric Administration (NOAA), 

 encompasses nearly 32 km 2 at a 

 depth of about 22 m. Compared with 

 surrounding areas, Gray's Reef con- 

 tains extensive, but patchy and dis- 

 continuous, hardbottom of moder- 

 ate relief (up to 2 m). Rock outcrops 

 or "ledges" have formed in a north- 

 west to southeast direction (Fig. 1 ). 



Ledges are often separated by wide 

 expanses of sand and are subject to 

 weathering, shifting sand, and 

 slumping, which create a complex 

 habitat with caves, burrows, troughs, 

 and overhangs (Hunt, 1974). Sandy 

 areas between the ledges consist of 

 coarse shell with varying amounts 

 of "rock-like" litter (Henry and Van 

 Sant 1 ). 



Reef fish assemblages are diffi- 

 cult to sample because of the diver- 

 sity and mobility of the fauna and 

 because of the variety of microhabi- 

 tats within complex reef substrates 

 (Russell et al., 1978). The applica- 

 bility and limitations of various 

 techniques for estimating reef fish 

 abundance have been reviewed 

 (Russell et al., 1978; Sale, 1980; 

 Sale and Douglas, 1981; Brock, 

 1982; DeMartini and Roberts, 1982; 

 Sale and Sharp, 1983; Kimmel, 

 1985; Sanderson and Solonsky, 

 1986; Bortone and Kimmel, 1991). 



Henry, V. J., Jr., and S. B. Van Sant. 1982. 

 Results of reconnaissance mapping of the 

 Gray's Reef National Marine Sanctuary, a 

 report prepared for the Georgia Depart- 

 ment of Natural Resources, Coastal Re- 

 sources Division, Brunswick, GA, under co- 

 operative agreement with the Sanctuary 

 Programs Division of the National Oceanic 

 and Atmospheric Administration (No. 

 NA81AA44-C2098, Amendment 1), 21 p. 



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