222 
Fishery Bulletin 11 6(3-4) 
Table 1 
Sampling effort by net type within the St. Johns River, Florida, during the summers of 2014 and 2015 in our 
study of the seasonal occurrence of Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus). 
Year 
Gill nets 
Trammel nets 
Annual totals 
No. of sets 
Soak time (h) 
No. of sets 
Soak time (h) 
No. of sets 
Soak time (h) 
2014 
30 
24 
1 
1 
31 
25 
2015 
105 
127 
14 
22 
119 
149 
Combined totals 
135 
151 
15 
23 
150 
174 
Results 
Sampling of sturgeon 
Initial sampling was conducted from 25 June through 
2 July 2014 to identify suitable sampling sites within 
the estuary where anchored nets could be safely fished 
without impeding commercial or recreational vessels. 
During this period, we set 31 nets for a total of 24.3 h 
of soak time (Table 1). Between 23 June and 10 July 
2015, we set 119 nets for a total of 149.4 h of soak 
time. Only one MMJ Atlantic sturgeon (786 mm FL, 
920 mm TL) was captured during this study, and sub¬ 
sequent genetic analysis assigned this individual to the 
population of the Altamaha River, Georgia, with 98% 
probability (Wirgin 6 ). 
Acoustic telemetry 
The single Atlantic sturgeon captured at rkm 40 in 
July 2015 was was tagged with an acoustic tag, but 
it was never detected on the acoustic array. The ar¬ 
ray did, however, detect 8 previously tagged Atlantic 
sturgeon that had been captured and released by other 
researchers working outside St. Johns River (Table 2, 
Fig. 1). At the time of tagging, these individuals were 
either MMJs (n= 3) or adults (n=5). We examined data 
recorded by the acoustic receivers from June 2014 
through June 2016. All detections of Atlantic sturgeon 
obtained during the period of this study occurred in 
winter or early spring (Figs. 2 and 3)—a temporal pat¬ 
tern that was consistent in both 2014 and 2015. Most 
of these migrant Atlantic sturgeon (n= 5, 62.5%) were 
never detected upriver from receiver STJ02 (rkm 9), 
and only one individual (12.5%) was detected as far 
upstream as receiver STJ06 (rkm 48). 
Water quality 
During the summer sampling period, mean daily wa¬ 
ter temperatures in the St. Johns River estuary were 
comparable to those obtained in other nearby rivers 
6 Wirgin, I. 2017. Personal commun. Sch. Med., New York 
Univ., 57 Old Forge Rd., 2 nd FL, Tuxedo, NY 10987. 
where populations of Atlantic sturgeon have been well 
documented (Table 3, Fig. 4). Dissolved oxygen levels 
in the St. Johns River were also well within the range 
of those observed in other rivers of the southeastern 
United States with extant populations of Atlantic stur¬ 
geon (Table 3, Fig. 5). 
Discussion 
After expending 174 net hours of sampling effort dis¬ 
persed over 150 individual net-sets, we could not con¬ 
firm the presence of a juvenile cohort of Atlantic stur¬ 
geon within the St. Johns River estuary. Our sampling 
efforts included many of the same sampling sites used 
in previous surveys of sturgeon in the St. Johns River 
(Holder et al. 3 ), and these sites were primarily estab¬ 
lished on the basis of incidental captures of sturgeon in 
commercial and recreational fisheries that target other 
species. Although salinities at specific sampling sites 
varied depending on tidal cycle and seasonal precipita¬ 
tion, the range of salinities that we observed within 
our sampling area was similar to those documented 
in other nearby rivers (e.g., Altamaha and Satilla riv¬ 
ers in Georgia) where several RRJ cohorts have been 
documented in recent years (Schueller and Peterson, 
2010; Bahr and Peterson, 2016; Fritts et al., 2016). 
Likewise, water temperatures and levels of dissolved 
oxygen at sampling sites in this study were well within 
the known tolerances of juvenile Atlantic sturgeon and, 
again, were comparable to those in other nearby rivers 
with extant populations of Atlantic sturgeon. Genetic 
analysis of the tissue sample obtained from the single 
Atlantic sturgeon captured indicates that this fish was 
almost certainly a subadult migrant from the Altama¬ 
ha River. 
During 2 summers of sampling in the St. Johns 
River, we captured no RRJ Atlantic sturgeon. Concur¬ 
rent sampling was conducted in several nearby estu¬ 
aries, including the Ogeechee and Altamaha rivers in 
Georgia and St. Marys River on the border of Georgia 
and Florida; the same methods and gear successfully 
captured RRJ Atlantic sturgeon in those rivers (senior 
author and D. Peterson, unpubl. data). Furthermore, 
the catch rate for Atlantic sturgeon (at all life stages) 
