We collected biological, health, and parasite-infection (e.g., Anguillicoloides crassus [a swim-bladder nematode]) data for 609 Anguilla rostrata (American Eel), and population-genetics data from a subset of 299 individuals captured throughout Florida from 2014 through 2016. We did not find evidence of genetic differentiation between groups and concluded that a single American Eel stock extends through the Atlantic-coast drainages into the Gulf of Mexico. We found spatial and seasonal differences in swim-bladder condition and in prevalence and incidence of A. crassus infection in Florida's American Eels. Average values for the ratio of swim-bladder to length and health indices were similar between regions, among seasons, and between uninfected and infected American Eels. Information gathered by this study will be important in future conservation and management efforts.