Fox et al.: Seasonal occurrence of Acipenser oxyrinchus oxyrinchus in the St. Johns River, Florida 
225 
Figure 4 
Mean daily water temperature (°C) measured at sampling sites in the 
St. Johns River in Florida and in the Altamaha and Satilla rivers in 
Georgia during June-July 2015. 
Date 
Figure 5 
Mean daily levels of dissolved oxygen (mg/L) measured at sampling 
sites in the St. Johns River in Florida and in the Altamaha and Satilla 
rivers in Georgia during June-July 2015. 
from the St. Johns River—the absence of evidence is, 
by no means, conclusive evidence of absence. Atlan¬ 
tic sturgeon are long-lived, intermittent spawners, 
and several previous studies have shown that rem¬ 
nant populations can be extremely difficult to detect 
even with intensive sampling efforts. For example, 
populations of Atlantic sturgeon were, until recently, 
thought to be extirpated from the St. Marys River, 
an adjacent river located only 34 km north of the St. 
Johns River (Blair et al. 7 ). Recent sampling in that 
river system, however, has documented the presence 
of an RRJ cohort in that system, confirming the pres- 
7 Blair, S., M. Ezell, H. Hall, and J. November. 2009. St. 
Marys River watershed. Prepared for the St. Marys River 
Management Committee in collaboration with the University 
of Florida Conservation Clinic and the University of Georgia 
Environmental Law Practicum. [Available from website.] 
