226 
Fishery Bulletin 11 6(3-4) 
ence of an extant population (senior author and D. 
Peterson, unpubl. data). Despite the limited sample 
size obtained there, preliminary genetic analyses of 
tissue samples from those juveniles indicate that they 
represent a unique population within the DPS for the 
southeastern United States, one likely produced from 
a remnant population of subadults that survived the 
era of commercial fishing (Wirgin 6 ). 
Although the St. Johns River channel has been 
dammed and dramatically altered, the river still poten¬ 
tially could support a population of Atlantic sturgeon. 
Water temperatures and levels of dissolved oxygen 
measured during this study were quite comparable to 
those in nearby rivers with extant populations. Conse¬ 
quently, we emphasize that additional assessments are 
needed in the future (every 2-3 years) to definitively 
ascertain the status of Atlantic sturgeon within the 
St. Johns River system. If neither RRJs nor spawning 
adults can be captured in future studies, the use of 
modern environmental DNA (eDNA) methods could be 
used to help establish the presence of spawning adults 
within the upper reaches of the St. Johns River. A simi¬ 
lar approach was used recently by Pfleger et al. (2016) 
to document the presence of the Alabama sturgeon 
(Scaphirhynchus suttkusi) in the Mobile River basin, 
Alabama. 
The data collected in this study confirm the seasonal 
presence of both adult and MMJ Atlantic sturgeon in 
the lower St. Johns River estuary during the late win¬ 
ter and early spring months. The seasonal presence of 
adult and MMJ individuals was detected on all acous¬ 
tic receivers within our array. All 8 migrants originally 
had been tagged in either the mid-Atlantic or south¬ 
eastern United States, indicating that the St. Johns 
River may still provide important wintering habitat for 
nonresident Atlantic sturgeon. Similar movement pat¬ 
terns have been documented in several other river sys¬ 
tems of the southeastern United States (senior author 
and D. Peterson, unpubl. data); however, more infor¬ 
mation is needed to better understand the seasonal im¬ 
portance of nonspawning migrations. Regardless, the 
results of this study indicate that adult fish are most 
abundant in the St Johns River estuary during the 
late winter and early spring. As range-wide recovery of 
Atlantic sturgeon continues, seasonal abundance with¬ 
in the lower St. Johns River will likely increase even 
in the absence of a natal population. Consequently, 
we emphasize the need for future studies with sample 
sizes larger than those in our study because the use of 
larger sample sizes will help to better define seasonal 
patterns of habitat use by migrating Atlantic sturgeon 
within the St. Johns River estuary. 
Acknowledgments 
This work was funded by the Naval Facilities Engi¬ 
neering Command Southeast, U.S. Department of the 
Navy; the National Marine Fisheries Service (NMFS); 
and the National Institute of Food and Agriculture, 
U.S. Department of Agriculture. Our thanks to C. Wat- 
terson, D. Fox, M. Loeffler, J., W. Post, J. Galvez, C. 
Williams, I. Wirgin, D. Kazyak, T. King, and D. Hig¬ 
ginbotham. This study was conducted under NMFS 
Permits 16482, 16507, 16442, 16422, and 16375, and 
the University of Georgia Animal Use and Care Permit 
A2013 01-012-Y3-A1. 
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