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Summer habitat use and relative abundances of different size classes of yellow perch (Perca fk-ivescens) were determined using gill nets set in the main basin, deep bays, and shallow bays of a lake. Niche overlap indices were used t s quantify resource use patterns. Size classes spatially segregated into different habitats, but not different depths within a habitat type. Segregation of sexes at different depths was observed with females occupying warm, shallow areas, whereas males were more common in coo!, deep water. Formation of an anoxic hypolimnion restricted perch to the epiiimnion in late summer, but patterns of habitat segregation observed prior to thermocline formation were maintained. Food partitioning was relatively unimportant in reducing niche overlap. Spatial segregation of perch size classes and sexes may compensate for high diet overlap between conspecifics and reinforces the importance of habitat parti-tioning in structuring fish communities. On a 6tudi6 I'utilisation de I'habitat estival et l'abondance relative des differentes categories de taille de la perchaude (Peaca flavescens) par des echantillonnages au filet maillant effectues dans le bassin principal, les baies prsfondes et Bes baies peu profondes d'un lac. Pour quantifier t'utilisation des ressources, on s'est servi d'indices de recoupement des niches. Les differentes categories de taille occupaient des habitat