The use of discrete group censusing for assessment and monitoring of reef fish assemblages

The accuracy and precision of a new method of visually assessing reef fish assemblages were tested in the "The Living Seas" at Walt Disney World's EPCOT Center (the world's largest aquarium) and in the Key Largo National Marine Sanctuary. The new method, called Discrete Group Censusing, involves dividing the total number of species to be censused into separate groups of 4-5 species. Each discrete group is then censused separately along a consistent path for 20 minutes. All groups are then combined to form a more accurate picture of the assemblage structure. The Discrete Group Censusing method was tested against a traditional strip transect method in which all species are sampled simultaneously. This new method was found to be far more precise and accurate than the strip transect method which is commonly used for assessment and monitoring of reef fish assemblages.; The Discrete Group Censusing method was then used to assess and monitor five coral reef fish assemblages in the Key Largo National Marine Sanctuary. Samples were obtained quarterly from Winter 1988 to Fall 1990 to investigate a possible relationship between the variability of reef fish assemblages and human disturbance. Two types of disturbances were studied; a ship grounding that had occurred four years previously, and intensive sport skin and SCUBA diving. These disturbances appeared to have no short-term effect on the temporal variability of the reef fish assemblages during the study period. Furthermore, the assemblages at all five study sites appeared to be extremely stable over the two year period of the study. These results support the theory that coral reef fish assemblages are highly ordered and stable over relatively large spatial scales.