This dataset is from a study of a simulated angling tournament livewell holding in June of 2023 on Largemouth Bass (Micropterus nigricans) on Clinton Lake, Illinois. Fish were collected via electrofishing, weighed, measured and assessed for physical injury prior to receiving a commercially available cull tag and being placed in a simulated livewell. After a six hour livewell holding period, fish were removed from the livewell assessed for physical injury and then assessed for reflex action mortality predictors prior to being placed in a net pen for 3 days of observation. This dataset includes, weights, total lengths, physical injury scores, and reflex action mortality predictor scores for Largemouth Bass and water quality parameters of livewells and the lake in net pens.