Fox et al.: Juvenile Agpenser oxyrinchus desoto/ in the Apalachicola River in Florida 249 
the JWLD was never detected in the Brothers 
River, but it was detected with receivers in the 
ME Tagged Apalachicola Estuary as it moved downriver in 
==) Detected the fall. 
[-—_) Confirmed survived 
20-4 
Recruitment 
—s 
oa 
——— 
Model selection on the basis of AICc values indi- 
cates that the M,,, model (with the additive effect 
of time and age) held almost all of the weight in 
most years of the study; the M,., model (with the 
interactive effect of time and age) held the most 
weight in only 2 years (Suppl. Table 2) (online only). 
For the age-1 cohort, weighted averaging of all 
models resulted in estimated abundance of 28-54 
individuals in each year of the study, except for 
2014, for which the estimated abundance of age-1 
fish was 210 individuals (Fig. 4). 
ie 
oO 
1 
No. of individuals 
2015 2016 
Year 
Figure 3 
Deployment and detection of acoustic tags on and fate of age-1 Gulf Survival 
sturgeon (Acipenser oxyrinchus desotoi) captured and tagged in the 
Apalachicola River in Florida during 2014-2017. Black bars indi- Of the 38 acoustic transmitters that we deployed 
cate the number of age-1 fish implanted with acoutic transmitters on Gulf sturgeon and later detected in our array, 
in each year of this study, and gray bars indicate how many of those : laetiictoctcduin IMorchbor 
transmitters were subsequently detected by the acoustic receiver 24) ransmnitters were AST CeLeCte in 
array. Open bars indicate the number of individuals confirmed to later of the following calendar Vea (i.e., the fish 
have survived to at least age 2, through a combination of detections implanted with the transmitters survived the 
with telemetry data and physical recapture of fish. winter after tagging). An additional 7 tagged fish 
that were never detected by the array were phys- 
ically recaptured >1 sampling season after tag- 
ging. We have confirmed that 31 fish (62% of all 
recaptured in nets—something we did not observe in any tagged fish) survived to at least age 2. Our conservative 
other study year. estimates of overwinter survival varied annually from a 
During summer months, individuals tagged in the low of 33.3% to a high of 90.0% (mean: 60.2% [standard 
Brothers River remained there almost exclusively. In deviation (SD) 27.8]) (Fig. 3). 
2014, one fish was briefly detected by a receiver 
in the main stem Apalachicola River near the 
mouth of the Brothers River but returned to the 
Brothers River within about 3 h of that detection. 
In 2017, another tagged fish was detected at a 
receiver at the mouth of the Brothers River and 
may have entered the Apalachicola River (it was 
never detected by receivers there); that fish was 
detected again at the same gate receiver 18 d 
later. Recapture of fish (in gill nets) and sporadic 
active tracking of tagged fish confirmed their 
presence in the Brothers River even when fish 
were not detected by the acoustic receiver array 
Annual no. of recruits 
(e.g., they were between 2 receivers and out of 50 
the detection range of both). During opportunis- r 4 
tic hydrophone sweeps, tagged age-1 fish were 0 
never detected outside of the Brothers River. 2013 2014 2015 2016 2017 2018 
The juveniles moved out of the Brothers River Year 
in the fall and were detected with receivers in Figure 4 
the main stem Apalachicola River and its dis- 
tributaries as they moved toward Apalachicola 
and East Bays. Tagged fish were detected mov- 
ing back up these same channels toward and 
into the Brothers River the following spring. 
The single Gulf sturgeon acoustically tagged at 
Estimates of abundance of age-1 juvenile Gulf sturgeon (Acip- 
enser oxyrinchus desotoi), by year that a cohort was sampled, in 
the Apalachicola River in Florida during 2013-2018. Abundance 
is measured as the number of recruits. Error bars indicate 95% 
confidence intervals. 
