Overwinter survival, age, and growth of juvenile tarpon (Megalops atlanticus) in a shallow, tidally-restricted habitat in South Carolina

Early life stage tarpon (Megalops atlanticus) have been collected in the western Atlantic Ocean north of Florida where it has been assumed that individuals migrate from estuarine areas at the onset of winter because water temperature during winter is too low for survival. However, there is anecdotal evidence of juvenile tarpon present during winter in this region. We conducted a tag-recapture study to examine potential overwinter survival in a tidally-restricted, upland pond in coastal South Carolina where tarpon have been observed during winter months. We also estimated the age structure of tarpon in this location to determine if age-0 fish were temporarily using this pond or if there were older individuals present, indicating the pond may be occupied for extended periods of time. We recaptured 29 of the 95 individuals tagged and released during January 2016 through October 2018. Of those 29 recaptured individuals, 13 survived one winter and two survived over two winters. Water temperature during winter in a nearby tidal creek was lower than in the pond, which appeared to provide a thermal refuge for tarpon. Estimated ages for 36 individuals ranged from 0 to 3 years (n = 10, 20, 5, 1, respectively). To our knowledge this is the northernmost documented overwintering of juvenile tarpon. Determining the extent of this type of habitat in the region and examining the population dynamics of tarpon in these locations could ultimately help determine how this region contributes to the productivity of adult tarpon populations.