L. E. MIRANDA AND M. S. ALLEN, Mississippi Cooperative Fish and Wildlife Research Unit, P.O. Drawer BX, Mississippi State, Mississippi 39762, USA

Dissolved oxygen concentrations in areas with abundant aquatic macrophytes are often reduced to levels seemingly unsuitable for most fish species. Yet, abundance of fish within aquatic macrophytes is high. Our objective was to investigate how juvenile largemouth bass are able to inhabit densely vegetated sites that often have unsuitable oxygen levels. We measured oxygen levels and largemouth bass abundance in vegetated and unvegetated sites, to document fish distributions relative to oxygen levels. Then, we tested (1) if fish left densely vegetated sites during periods of low oxygen concentrations, and (2) if variability of dissolved oxygen concentrations within densely vegetated sites allowed fish to find refugia with tolerable oxygen levels. Our results suggest that fish do not leave vegetated areas during periods of low oxygen. Instead, horizontal and vertical variability in dissolved oxygen concentrations within plant beds allow fish to find areas which meet minimum oxygen requirements.