LONG-TERM PATTERNS OF MICROHABITAT USE BY FISH IN A SOUTHERN APPALACHIAN STREAM FROM 1983 TO 1992 - EFFECTS OF HYDROLOGIC PERIOD, SEASON AND FISH LENGTH

We quantified microhabitat use by members of a southern Appalachian st ream fish assemblage over a ten-year period that included both floods and droughts. Our study site (37 m in length) encompassed riffle, run and pool habitats. Previous research indicated that species belonged t o either benthic or water-column microhabitat guilds. Most species exh ibited non-random microhabitat use in all seasons, and benthic and wat er column species generally were over-represented in the deeper portio ns of the sire, In addition, water column species generally were overr epresented in microhabitats with lower average velocities. The majorit y of seasonal shifts in microhabitat use were passive (i.e. correlated with changes in microhabitat availability), whereas, most shifts asso ciated with hydrological periods appeared to be active responses to ch anging environmental conditions, Most species exhibited length-related shifts in microhabitat use, which were strongly affected by hydrologi c period for four of ten species. Microhabitat use patterns of assembl age members appeared to be a consequence of species-specific responses to changing environmental conditions, The highly flexible patterns of microhabitat use exhibited by these species necessitate that decision s regarding their management be based on data covering a range of envi ronmental conditions.