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Reef fish assemblage survey results using Transect, Point, and Random in situ visual assessment techniques were evaluated and compared on a coral reef biotope off the southwestern coast of Puerto Rico. Parameters compared were: number of species, number of individuals, and species diversity (H'). No significant effect attributable to the time-of-day when the surveys were conducted was noted to occur. Variability in observations between divers was not noted for any of the dependent variables while conducting the Transect method. Divers using the Random technique recorded the highest number of species per survey, while the assemblage parameters recorded using Transect and Point methods were statistically similar for most dependent variables. Point surveys, however, had a higher and less variable species diversity. When the data were adjusted for amount of survey time and area it was determined that divers were more efficient in sampling numbers of individuals when using the Transect method.Recently, an interest has developed in the underwater visual assessment of reef fishes (e.g., Barans and Bartone 1983;Harmelin-Vivien et a/. 1985). This interest is due to several reasons as natural reefs serve as important biotopes for testing evolutionary/ecological hypotheses (see Bartone eta/. 1986 for a partial review). Additionally, to assess the relative "health" of natural reefs in terms of productivity, accurate community data are required. Furthermore, advances in the technology of artificial reef design (Buckley et a/. 1985) depend on the development of accurate, quantitative data on fish community abundance and biomass (Bohnsack and Sutherland 1985).Visually gathered reef fish abundance data avoids the substrate disrupting effects of traditional, surface tended collecting devices such as trawling (Bardach 1959 , Brock 1982, DeMartini and Roberts 1982, Kimmel 1985, Sanderson and Solonsky 1986. These studies have used various visual methods to assess fish abundance and employed several analytical techniques to clarify some problems but there remains no clear consensus as to what method is the "best" for all or any specific set of conditions.To help answer this methodological question, two observers compared six different methods under a variety of reef conditions (Bartone eta/. 1986). The conclusion of that study was that all of the compared methods are roughly equivalent in their ability to qualitatively describe a fish assemblage. Methods that produce the most information (i.e., number of species and number of individuals) tend to have less variance and more accurately associate environmental parameters with a particular assemblage. Also, the amount of sample time (and perhaps area) appears to be the most significant variable affecting the similarity of assemblage assessments, regardless of method. This suggests that, of the methods tested, those which produce the greatest amount of information in the least amount of time (or area surveyed) would be the most effective. Given that conventional scientific di...

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