Nesting preference for areas cleared of woody debris over areas cluttered with such debris was indicated by more nesting in cleared areas at the beginning and end of the breeding season, and more spawning activity in cleared areas. During heavy nesting, however, no preference was observed due to the density-dependent constraint of a high breeding population limiting available nesting space. This lack of difference in nesting densities at peak times indicates that breeding density cannot be enhanced in pumpkinseed sunfish by the creation of additional environmental boundaries. Nest density was influenced by the type of substrate of the site. In cluttered sections, nest diameters and distances to nearest cover were less than, and nearest neighbor distances not sigrificantly different from, those in cleared sections.