603 
Abstract.— Hypoxia in Chesapeake 
Bay has increased during the past cen- 
tury, coincident with the disappearance 
of Atlantic sturgeon spawning stocks. 
We hypothesized that Atlantic sturgeon 
young-of-the-year (YOY) might be more 
susceptible than other estuarine fishes 
to high temperature and low oxygen 
conditions, now prevalent in Chesa- 
peake Bay. Atlantic sturgeon ( 10-70 g) 
were reared under conditions of hy- 
poxia (2-3 mg/L dissolved oxygen) and 
normoxia (6-7 mg/L) at 19°C and 26°C 
for 10 days. High-temperature hypoxia 
resulted in lower survival (mean=6.3%) 
and respiration rate (mean=0.136 mg 
OgAg-h)). Low-temperature hypoxia re- 
sulted in a mean survival of 78% and 
mean respiration rate of 0.212 mg/(g h). 
Under hypoxia, mean weight-specific 
growth rate was 1.27%/d, ca. threefold 
less than growth under normoxia. Tem- 
perature alone did not significantly af- 
fect growth rates. When sturgeon were 
denied access to the surface, growth 
rates were significantly diminished in 
both normoxic and hypoxic treatments. 
At low ambient oxygen levels and high 
temperature, denial of surface access 
was fully lethal within 30 hours. We 
conclude that increased incidence of 
summertime hypoxia during this cen- 
tury has degraded sturgeon nursery 
habitats in Chesapeake Bay. 
Manuscript accepted 6 October 1997. 
Fishery Bulletin 96:603-613 ( 1998). 
Effects of hypoxia and temperature 
on survival, growth, and respiration 
of juvenile Atlantic sturgeon, 
Acipenser oxyrinchus * 
David H. Secor 
Troy E. Gunderson 
Chesapeake Biological Laboratory 
Center for Environmental and Estuarine Studies 
The University of Maryland System 
PO. Box 38, Solomons, Maryland 20688-0038 
E-mail address: secor@cbl.umces.edu 
An economically important popula- 
tion of Atlantic sturgeon, Acipenser 
oxyrinchus, once inhabited Chesa- 
peake Bay. During the late nine- 
teenth century, Chesapeake Bay 
supported the second greatest caviar 
fishery in the eastern United States 
(Murawski and Pacheco, 1977). In 
the early 1900s, the population col- 
lapsed. In Maryland, fishery land- 
ings declined from 74,500 kg, in 
1904, to 320 kg in 1920 (Hildebrand 
and Schroeder, 1928). Atlantic stur- 
geon have not recovered in Chesa- 
peake Bay (Spier and O’Connell, 
1996). The last fish legally har- 
vested in Chesapeake Bay, a mature 
female, was captured in 1970 from 
the Potomac River. The spawning 
population of Atlantic sturgeon may 
have been extirpated from Chesa- 
peake Bay (Speir and O’Connell, 
1996; Grogan and Boreman * 1 ). 
State, federal, academic, and non- 
profit organizations have begun to 
mobilize public interest and support 
for an aquaculture-based restora- 
tion program for Atlantic sturgeon 
in Chesapeake Bay. A principal as- 
sumption for Atlantic sturgeon res- 
toration is that deleterious conditions 
that led to the extirpation of the popu- 
lation (e.g. loss of habitat or over fish- 
ing) are now abated. Therefore, it is 
critical to evaluate possible causes for 
Atlantic sturgeon extirpation from 
Chesapeake Bay before state and fed- 
eral agencies move forward with a 
large-scale aquaculture-based resto- 
ration program. 
We hypothesize that increased 
hypoxia in Chesapeake Bay re- 
sulted in reduced habitat for Atlan- 
tic sturgeon and contributed to their 
decline. During this century, peri- 
odic increases (albeit small) in At- 
lantic sturgeon abundances have 
occurred in the southern and north- 
ern extent of the species’ range 
(Murawski and Pacheco, 1977). 
However, no evidence exists for pe- 
riodic recoveries of Atlantic stur- 
geon in Chesapeake Bay. The period 
of population decline and low abun- 
dance in Chesapeake Bay corre- 
sponds to a period of poor water 
quality, from 1950 to present, 
caused by increased nutrient load- 
ing and increased spatial and tem- 
poral frequency of hypoxia (Officer 
et al., 1984; Mackiernan, 1987; Jor- 
dan et al., 1992; Kemp et al., 1992; 
Cooper and Brush, 1993). 
* Contribution 3060 of the Chesapeake Bio- 
logical Laboratory, Center for Environmen- 
tal Science, University of Maryland, Solo- 
mons, MD 20688-0038. 
1 Grogan, C. S., and J. Boreman 1997. De- 
termining the probability that historical 
populations of fish species are now extir- 
pated. Unpubl. manuscr., U. Mass. Am- 
herst, MA, 25 p. 
