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rupestris) and longear sunfish (Lepomis megalotis). I studied behavior of individual fish by underwater observation and telemetry; documented population characteristics of density, biomass, and condition; and attempted to relate habitat use by individuals to the well-being of the population. I documented daytime habitat use in summer using underwater observation. After I corrected for differences in the amount of open water and each cover type observed, over 90% of individuals of each species were found to be positioned within 1 m of cover. Overlaps in cover use between species sug- gested that cover is not important in interspecific segregation. Species segregation was strongest by current velocity, with small mouth bass using cover in the fastest water and longear sunfish using cover in the slowest water. Current velocity was also im- portant to smallmouth bass and longear sunfish as an element of intraspecific segregation. Strong positive linear relations between water depth and fish size were noted for all three species, but water depth was not important in interspecific segrega- tion. Substrate use appeared to be dependent on cover use, and results were inconclusive. All three species shifted habitat throughout the day, but the greatest shifts occurred at night. Telemetry studies on small mouth bass substan- tiated the observational studies and added informa- tion on fish habitat associations in winter, when fish used boulders almost exclusively. Both studies showed that small mouth bass avoided shallow areas and existed almost exclusively in current velocities <0.2 m/s. I believe that the results of studies em- phasizing individual fish can be used with other studies to delineate essential habitat conditions for smallmouth bass populations. Regression models from population studies showed that depth and current did not correlate with standing crop of smallmouth bass. Perhaps these variables are important but are available in greater ~ ~~ounts than needed. What the regression model ~ show is that boulders had a positive relation ~ - '- ~ , CENTRARCHID-HABITAT ASSOCIATIONS 19 to standing crops. Perhaps boulders are an essen- tial habitat or a limiting factor for smallmouth bass in these streams because of some important, yet still unclear, function during cold-water periods. Fish may be more energetically efficient when associated with boulders during stressful periods. The significant, positive, but weak relation between boulders and fish density or biomass indicates that fish use boulder areas in a nonlinear fashion. Under- water observations indicated that a single boulder properly situated could accommodate as many as eight adult smallmouth bass. Thus, while a particular aspect of the habitat may be essential, its quality may be far more important than its quantity. These studies suggest that obtaining the information necessary for effective management of a fish popula- tion requires several approaches, and all these ap- proaches have to be repeated for different life stages. Information Sources Covington, W. G., R. E. Marteney, and C. F. Rabeni. 1983. Population characteristics of rock bass and smallmouth bass in the Ozark National Scenic Riverways. Trans. Mo. Acad. Sci. 17:27-35, McClendon, D. D., and C. F. Rabeni. 1986. A comparison of electrofishing and underwater observations in evaluating population characteristics of stream centrar- chids. Proc, Annu. Conf. Southeast. Assoc. Fish Wild!. Agencies 40:92-10l. Probst, W" C. F. Rabeni, C. G. Covington, and R. E. Marteney. 1984, Resource partitioning between stream- dwelling rock bass (Ambloplites rupestris) and small- mouth bass (Micropterus dolomieui). Trans. Am. Fish. Soc. 113:283-294. Rabeni, C. F., D. D. McClendon, W. Probst, B. Todd, A. Livingstone, and D. I. Foster. 1990. Management of smallmouth bass (Micropterus dolomieui) in the Ozark National Scenic Riverways, Proceedings of the Con- ference on Science in the National Parks, July 1986, Fort Collins, Colo. In press. Todd, B. L., and C. F. Rabeni. 1989. Movement and habitat use by stream-dwelling smallmouth bass. Trans. Am. Fish. Soc, 118:229-242.