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The EPA recognized in the biological evaluation that dissolved oxygen criteria for 
June through September for the deep-water seasonal fish and shellfish and the deep- 
channel designated uses were at or below levels that protect shortnose sturgeon. The 
EPA believed there were strong lines of evidence that shortnose sturgeon historically 
have not used deep-water and deep-channel designated use habitats during the 
summer months due to naturally pervasive low dissolved oxygen conditions based 
on the following: 
• Published findings in the scientific literature regarding salinity preferences (tidal 
fresh to 5 ppt) and salinity tolerances (<15 ppt) clearly indicated shortnose stur¬ 
geon habitats were unlikely to overlap with the higher salinity deep-water and 
deep-channel designated use habitats. 
• The EPA concluded, based on extensive published scientific findings and in-depth 
analysis of the 1400 record U.S. Fish and Wildlife Service Reward Program data¬ 
base, that these same deep-water and deep-channel regions have not served as 
potential habitats for sturgeon during the June through September time period 
when there is a natural tendency for low dissolved oxygen conditions to occur. 
• The EPA recognized the potential limitations of the U.S. Fish and Wildlife Service 
data set. However, the EPA believed the significant extent of the capture records— 
400 stations and 1400 individuals caught—provided substantial evidence for the 
lack of a potential conflict between shortnose habitat and seasonally applied deep¬ 
water and deep-channel designated uses. 
The EPA determined that the recommended dissolved oxygen criteria for the refined 
designated uses would not likely adversely affect the listed species evaluated in this 
document. Furthermore, the EPA determined that the Chesapeake Bay dissolved 
oxygen criteria would beneficially affect critical habitat and food sources on which 
the listed species was dependent. 
BIOLOGICAL EVALUATION CONCLUSIONS 
Shortnose sturgeon are endangered throughout their entire range (NOAA National 
Marine Fisheries Service 2002). According to NOAA, in the Final Biological 
Opinion for the National Pollutant Discharge Elimination System Permit for the 
Washington Aqueduct, this species exists as 19 separate distinct population segments 
that should be managed as such. Specifically, the extinction of a single shortnose 
sturgeon population risks permanent loss of unique genetic information that is crit¬ 
ical to the survival and recovery of the species (NOAA National Marine Fisheries 
Service 2002). The shortnose sturgeon residing in the Chesapeake Bay and its tribu¬ 
taries form one of the 19 distinct population segments. 
Adult shortnose sturgeon are present in the Chesapeake Bay based on the 50 captures 
via the U.S. Fish and Wildlife Service Atlantic Sturgeon Reward Program. However, 
the presence and abundance of all life stages within the evaluation area itself are 
unknown. Preliminary published scientific evidence suggests that the shortnose 
chapter iii 
Key Findings Published in the EPA ESA Shortnose Sturgeon Biological Evaluation 
