Parker et al.: Reef fish abundance, composition, and habitat use 



797 



Table 4 



Ten most abundant and common hardbottom species observed by divers or caught by trawl. 



Trawls A 2 



Stenotomus eaprinus 

 Haemulon aurolineatum 

 Chromis enehrysurus 

 Monacanthus hispidus 

 Centropristis striata 

 Rhomboplites aurorubens 

 Calamus leucosteus 

 Holocanthus bermudensis 

 Equetus umbrosus 

 Apogon psuedomaculatus 



Trawls B 3 



Stenotomus eaprinus 

 Haemulon aurolineatum 

 Rhomboplites aurorubens 

 Equetus lanceolatus 

 Centropristis striata 

 Prionotus carolinus 

 Calamus leucosteus 

 Equetus umbrosus 

 Urophyeis regia 

 Monocanthus hispidus 



' This study, 22 m deep. 



8 Wenner, 1983; < 18-183 m deep, day and night catches combined. 



3 Sedberry and Van Dolah, 1984; 16-67 m deep. 



formed five counts of species and individuals 

 (Nicholson 4 ). Although all divers were experienced in 

 underwater surveys and were familiar with the 

 fauna, the mean percent similarity for the five teams 

 was only 57% and ranged from 47% to 64%. Video- 

 taping reduces the variance in error among observ- 

 ers and allows virtually unlimited time for study of 

 the images by many individuals ( Ebeling et al. , 1980 >. 

 In choosing between transect and point sampling, 

 we considered the particular conditions at GRNMS. 

 When properly applied, the precision of both proce- 

 dures can be high (Keast and Harker, 1976; Sale and 

 Douglas, 1981; DeMartini and Roberts, 1982; 

 Bohnsack and Bannerot, 1986; Witzig, 1988). Lim- 

 ited visibility at GRNMS was thought to bias point 

 counts for some species. Bohnsack and Bannerot 

 ( 1986) found that point samples with a radius of 2 m 

 or less underestimated abundances of 11 of 15 spe- 

 cies observed. In contrast, Parker ( 1990) found that 

 during low visibility some species of reef fish (e.g. 

 gag, black sea bass, and white grunt) concentrate 

 under and around ledges. Extrapolating density of 

 these fish in a small visible area to the total popula- 

 tion over an entire reef that consists mostly of low 

 profile (<1 m) rock outcroppings sparsely inhabited 

 by fishes grossly overestimates their abundance. Off- 

 bottom tidal currents, frequently in excess of 20 cm/s 

 at GRNMS, make it impossible for the vessel to re- 

 main stationary for the 5 to 10 minutes necessary to 

 conduct enumerations. For these reasons we devel- 

 oped a random transect technique that allowed us to 

 swim with the prevailing current, covering 86 to 544 

 m per transect. Because visibilities at GRNMS can 

 be consistently less than 5 m, this technique allowed 

 us to sample large areas with minimum underwater 

 time. The technique is a consistent, repeatable pro- 



cedure for assessing the noncryptic, diurnally active 

 fishes at GRNMS. 



Acknowledgments 



This work is the result of research sponsored by the 

 U.S. Department of Commerce, National Oceanic and 

 Atmospheric Administration, National Ocean Ser- 

 vice, Office of Ocean and Coastal Resource Manage- 

 ment, Sanctuary Programs Division, under contract 

 NA84DOC-C2004. We sincerely thank the Georgia 

 Department of Natural Resources, Coastal Resources 

 Division, and in particular the captain of the RV 

 George T. Bagby, the late David Ansley, and the crew, 

 Henry Ansley, Byron Kroscavage, and Tom and Matt 

 Dougherty, for the vessel, for diver support, and for 

 suggestions on survey methods. Special thanks is 

 extended to Dave Colby of this laboratory and two 

 anonymous reviewers for their suggestions and re- 

 views of the final drafts of the manuscript. Finally, 

 we thank Beverly W Harvey for typing and quick 

 turnaround of the many drafts of this paper. 



Literature cited 



Alevizon, W. S., and M. G. Brooks. 



1975. The comparative structure of two western 

 Atlantic reef fish assemblages. Bull. Mar. Sci. 

 25:482-490. 

 Anderson, G. R V., A H. Ehrlich, P. R. Ehrlich, 



J. D. Roughgarden, B. C. Russell, and F. H. Talbot. 

 1981. The community structure of coral reef fishes. 

 Am. Nat. 117:476-495. 

 Bardach, J. E. 



1959. The summer standing crop offish on a shal- 

 low Bermuda reef. Limnol. Oceanogr. 4:77-85. 



