Fox et al.: Juvenile Acpenser oxyrinchus desoto/ in the Apalachicola River in Florida 245 
age-1 juvenile cohorts over time could enable an investiga- 
tion of environmental factors, like salinity, that have been 
thought to influence recruitment during the first year of 
life of Gulf sturgeon (e.g., Nilo et al., 1996). 
Yet another unknown is the overwinter survival rate of 
juvenile Gulf sturgeon during the foraging period. While 
foraging in the estuary, juvenile sturgeon may be taken by 
bottom fisheries, such as shrimp traw]- 
ing fisheries (Wooley and Crateau, 1985; 
Collins et al., 2000). Although this poten- 
tial source of mortality has been noted 
over the years (USFWS and GSMFC’; 
USFWS and NMFS, 2009), estimation 
of the overwinter survival of juvenile 
sturgeon has not been attempted. Mon- 
itoring the overwinter survival of age-1 
Gulf sturgeon may provide insight into 
what happens to young juveniles after 
they recruit to the population and may 
allow comparisons of mortality across 
river systems that experience different 
pressures (e.g., bycatch in other fisheries 
or dredging). 
The goal of this 6-year study, therefore, 
was to investigate juvenile Gulf stur- 
geon in order to elucidate gaps associ- 
ated with this life stage. We selected the 
Apalachicola River system for this inves- 
tigation because information on where 
to target juvenile Gulf sturgeon was 
available from historical records of their 
incidental capture during monitoring 
of adults. The specific objectives of this 
study were to estimate the abundance 
of age-1 annual cohorts as a quantified 
measure of recruitment and to calculate 
a conservative estimate of the survival 
of age-1 juveniles during their estuarine 
overwintering period. 
Materials and methods 
Study site 
The Apalachicola River is the largest 
river by discharge in the state of Florida 
(Iseri and Langbein, 1974). The river is 
formed by the confluence of the Flint 
and Chattahoochee Rivers, although this 
junction is now inundated by the reser- 
voir created by construction of the Jim 
Woodruff Lock and Dam (JWLD). Down- 
stream of the JWLD, the Apalachicola 
River flows freely for 171 river kilo- 
meters (rkm) through the Florida 
Panhandle to Apalachicola Bay in the 
Gulf of Mexico (Fig. 1). Sampling efforts 
were concentrated in the Brothers River, 
Florida O 
O @) 
O Apalachicola : 
River e 
® 
85°10'W 
a tributary that flows into the Apalachicola River 21 rkm 
upstream of the bay. The Brothers River has a deep 
(9-15 m) channel that has been identified as a summer 
habitat for juvenile Gulf sturgeon (Wooley and Crateau, 
1985; Kirk and Killgore’; A. Kaeser, unpubl. data). Addi- 
tional sampling was conducted in several areas located in 
the lower and upper sections of the main stem Apalachicola 
84°50'W 
Lake 
Seminole 
Georgia 
Florida 
Florida 
O 
© Apalachicola 
ame §=JWLD 
USGS 
stream gage [ies] Sampling area 
02359170 Acoustic receivers 
2014-2016 
2014-2018 
2016-2018 
Brothers oO 
River fe) 2017-2018 
e 
@eeee N 
Apalachicola Bay rN 
84°55'W 84°50'W 
85°5'W 85°0'W 
Figure 1 
Maps of the study site in the Apalachicola River in Florida: (A) the Apalachicola 
River downstream of the Jim Woodruff Lock and Dam (JWLD, indicated by 
a black rectangle) and (B) the Brothers River and lower Apalachicola River. 
Sampling for juvenile Gulf sturgeon (Acipenser oxyrinchus desotoi) in 2014— 
2018 occurred within the boxes outlined in black. Circles indicate locations of 
acoustic receivers within the array installed for this study—open for receivers 
deployed during 2014-2016, black for those deployed during 2016-2018, half 
black for those deployed during 2014-2018, and three-fourths black for the 
receiver deployed during 2017-2018. In panel B, the location of U.S. Geological 
Survey (USGS) stream gage 02359170 on the Apalachicola River near Sumatra, 
Florida, is indicated. 
