The yellow bass (Morone mississippiensis) is a common, yet lesser known species of the Mississippi River drainage basin; few life history studies on the species have been published throughout its range. To describe population level gonad development, seasonal abundance, and age and growth, yellow bass were collected every 7-14 days with monofilament gill nets from 14 November 2008 to 17 November 2009 from the upper Barataria Estuary (UBE) in south Louisiana. Mean catch-per-unit effort (CPUE) was highest from February-April, indicating that yellow bass used the UBE seasonally. Yellow bass abundance peaked as temperatures reached 18-22 C. Total length, weight, and gonadosomatic index (GSI) were measured from each whole fish collected (n = 1043). Age was estimated using sagittal otoliths and annulus formation was confirmed by marginal increment analysis. Although yellow bass ranged from age 1 to age 4, the population was dominated (95%) by age 2 fish. Gonad samples (n = 200) collected throughout the year were examined histologically to determine spawning period. Spawning activity was confirmed by the presence of post-ovulatory follicle complexes in female gonads collected from January 2009-April 2009. Similarly, GSI noticeably decreased as temperatures reached 18-22 C, indicating spawning had occurred. The use of the UBE by yellow bass was related to spawning activity. The paucity of information on yellow bass throughout its range led to the development and conduction of this study which provides important seasonal use, age structure, and reproductive data for yellow bass in the lower Mississippi River drainage basin.