REGIONAL EVALUATION OF THE RELATION OF HABITAT TO DISTRIBUTION AND ABUNDANCE OF SMALLMOUTH BASS AND LARGEMOUTH BASS IN MISSOURI STREAMS

Fish-habitat models for streams were developed to help explain the dec line and possible replacement of smallmouth bass Micropterus dolomieu by largemouth bass M. salmoides in the Ozark Border region of Missouri . We identified habitat conditions associated with the distribution an d abundance of both species in sympatric and allopatric situations by means of correlation analysis and multiple linear regression models. M aximum summer temperature and percent pool area explained most of the variability in total densities, adjusted densities (fish larger than 1 00 mm total length), and biomass for both species. Smallmouth bass wer e negatively associated with each variable, whereas largemouth bass we re positively associated. Physical habitat that is unable as cover was not associated with the abundance of either species. Final models exp lained about 50% of the variation in the population characteristics of both species and showed good accuracy and precision across years. Adj usted-density models appeared to be the most appropriate management to ol and had the greatest predictive abilities across years. Results sug gest that human activities have altered stream environments to favor l argemouth bass populations in the Ozark Border region.