The Deepwater Horizon oil spill in the spring/summer of 2010 occurred during the peak spawning season of the blue crab Callinectes sapidus in the northern Gulf of Mexico. The potential for contamination of larvae by crude oil and dispersants associated with the spill was high given the life history of blue crabs. The oil spill occurred in offshore waters considered important for blue crab larval development and there was high spatial and temporal overlap between blue crab larvae and the incident area. Exposure to contaminants may have occurred in both the offshore developmental phase and the nearshore settlement stage. Fluorescence spectroscopy techniques were developed to detect polycyclic aromatic hydrocarbon contamination in composite samples of tissue of 50 megalopae. Samples as low as 400 µl were analyzed allowing for detection of contaminants in very small sample sizes. Evidence of petroleum contamination was found in all megalopae harvested from the wild.