Fox et al.: Seasonal occurrence of Acipenser oxyrinchus oxyrinchus in the St. Johns River, Florida 
221 
Legend 
* Sampling site 
☆ Sturgeon capture 
Receiver station 
20 
■ Kilometers 
_ 
3 Receiver River 
station kilometer 
STJ01 
6 
STJ02 
9 
STJ03 
18 
STJ04 
14 
STJ05 
22 
STJ06 
26 
STJ07 
48 
Atlantic Ocean 
Florida 
Figure 1 
Map of sites where sampling was conducted during 2014- 
2015, the location where an Atlantic sturgeon (Acipenser 
oxyrinchus oxyrinchus ) was captured in July 2015 (☆), and 
the stations (01-07) where acoustic receivers were deployed 
in the St. Johns River (STJ) in Florida. Inset A depicts the 
rivers of the southeastern United States, including several 
rivers nearby the St. Johns River with documented popula¬ 
tions of Atlantic sturgeon: Ogeechee (OGE), Altamaha (ALT), 
and Satilla (SAT) in Georgia and St. Marys (STM) along the 
border of Georgia and Florida. Approximate river kilometers 
(rkm) of the locations of the receivers from the mouth of the 
estuary are listed in inset B. 
transponder tag was injected under the 4 th 
dorsal scute and a small tissue sample was 
taken from the dorsal fin for genetic analysis. 
The fish was then placed on a custom-made, 
v-shaped surgical board that held the fish in 
lateral recumbency. A small bilge pump (473.2 
L/h) was used to maintain a gentle flow of river 
water over the gills. A sterile scalpel was then 
used to make a 1-cm incision along the midline 
of the ventrum for insertion of a 69-kHz Vemco 
V7-4x 5 sonic transmitter (Vemco, Bedford, Can¬ 
ada). The incision was closed by using a 2/0 ab¬ 
sorbable monocryl suture (Monoswif L943, CP 
Medical, Inc., Norcross, GA) as a simple suture 
with interrupted stiches as described by Boone 
et al. (2013). Once the incision was closed, the 
fish was allowed to recover and returned to the 
river at its original capture site. 
Fish ages were estimated by using a length- 
frequency histogram based on Schueller and 
Peterson (2010); individuals with TL<550 mm 
were considered to be age-1 RRJs. 
Acoustic telemetry 
A passive array of 7 stationary acoustic receiv¬ 
ers (Vemco VR2W) were distributed in June 
2014 throughout the St. Johns River estuary to 
monitor the spatial and temporal movements 
of acoustically tagged Atlantic sturgeon. The 
submerged acoustic receivers were attached to 
channel markers and other stationary struc¬ 
tures by using aluminum u-channel or stain¬ 
less steel cables and hardware. All acoustic 
receivers were affixed in an upright position, 
2-3 m below the surface to ensure that they re¬ 
mained completely submerged throughout the 
tidal cycle. Range testing conducted at receiver 
locations indicated an average tag detection ra¬ 
dius of approximately 400 m (range: 200-800 
m). Once the receivers were deployed, data 
from these acoustic receivers were downloaded 
every 3-5 months throughout the duration of 
this study. 
obstruction-free bottoms. On sampling days, crews set 
5-12 anchored gill and trammel nets perpendicular to 
the channel and soaked them for approximately 30- 
90 min, depending on conditions. Gill nets 91.4 m in 
length and 3.1 m deep, were composed of panels of 7.6-, 
10.2-, and 15.3-cm monofilament mesh (stretch mea¬ 
sure). Trammel nets were of similar dimensions and 
material and were composed of one 7.6-cm inner panel 
and three 30.5-cm outer panels. As nets were retrieved, 
entangled sturgeons were quickly removed and placed 
in a floating net pen. 
Once all nets had been recovered, each captured 
sturgeon was measured to the nearest millimeter (to¬ 
tal length [TL] and fork length [FL]) and was inspected 
for tags. If no tag was present, a passive integrated 
Water-quality 
To monitor variations in water quality throughout the 
sampling period, we collected measurements of water 
temperature (degrees Celsius), dissolved oxygen (milli¬ 
grams per liter), and salinity at each fish sampling site 
during June-July in 2015 and 2016. These measure¬ 
ments were obtained at the surface and at 0.5 m from 
the bottom at each netting site by using a portable YSI 
Pro2030 multiprobe (YSI, Inc., Yellow Springs, OH). 
5 Mention of trade names or commercial companies is for iden¬ 
tification purposes only and does not imply endorsement by 
the National Marine Fisheries Service, NOAA. 
