Comparative Accuracies of Visual Assessment Methods for Coral Reef Fishes

Four methods of visually assessing reef fish assemblages were compared in “The Living Seas” at Walt Disney World, EPCOT Center. An accurate “standard of reference” (proportionate abundance of 44 species) was provided by approximately 43 man-hours of repetitive sampling of small groups (1–6) of species. Twenty 5-min censuses were obtained by (1) a remotely operated vehicle (ROV), (2) a SCUBA diver recording observations on a plastic slate (Slate), (3) a diver using an underwater tape recorder (Audiotape), and (4) a diver using a video camera (Cinetransect). The methods were evaluated and compared on the basis of their ability to accurately estimate the relative abundances and rank orders of pools of 44 and 31 species. The relative efficiencies of the four methods were also compared. Here, efficiency was defined as the amount of time necessary to achieve a stabilized picture of assemblage structure. Of the four methods tested, the Audiotape was the most accurate and efficient in estimates of proportionate abundance. Species rankings (based on abundance) produced by all methods were highly correlated. Unexpectedly, a variation of the basic method used to determine the reference standard was found to be far more accurate, for about the same amount of sampling effort, than any of the methods tested. This method, herein called Discrete Group Censusing, is based on sampling only a few community members at a time, and combining these data into an overall picture of assemblage structure.