Eastern oyster, Crassostrea virginica, larval performance is dependent on ambient endogenous (i.e., physiological variation) and exogenous (i.e., environmental and food conditions) factors. In 2019, a mass mortality event decimated oyster populations in the western Mississippi Sound, ultimately causing the closure of the oyster fishery in the state of Mississippi. Slow recovery suggests impacted larval performance post-2019. Little is known about larval performance in relation to food particle size under field conditions. Monitoring of oyster food supply size composition in 2024 provides a basis for such an evaluation through the use of a biochemically based larval performance model. In this study, Mississippi Sound food composition data acquired in 2024 are evaluated by a larval performance model to investigate how the food assemblage interacts with larval performance, which may ultimately influence local oyster population recovery. The goal of this study is to relate real-time observations of local larval development with the food assemblage with respect to food size. Simulations with varying biochemical compositions within food assemblages and particle size compositions corroborate that food quality and quantity are important for larval growth, and further suggests that the size of the food available throughout larval development is impactful in the larva’s ability to undergo successful metamorphosis. Assessments of the food assemblage requires distinguishing these size classes are consistent with well-known size classes of phytoplankton (i.e. picoplankton, <5 mm; nanoplankton, 5-20 mm; and macroplankton, >20 mm).