Delaware River) use saline water the least. Adults
forage and spawn in fresh water for years, then en-
ter the fresh/saltwater reach, usually only briefly
(Buckley & Kynard 1985a, Dovel et al. 1992, O’Her-
ron et al. 1993, Kieffer &Kynard1993). This pattern
of fresh and saltwater use is termed freshwater am-
phidromy (Kieffer & Kynard 1993). Because feed-
ing occurs when temperature exceeds about 7° C
(Dadswell 1979), north-central rivers provide suit-
able thermal foraging conditions in fresh water for
about 7 months (April -October). This islikely the
longest continuous period of a suitable thermal re-
gime for foraging in fresh water. Adults in some
southern rivers (Cape Fear, Pee Dee, Savannah,
and Altamaha rivers) forage in or just upstream of
the fresh/saltwater interface moving to high salinity
water either briefly. or for a long period, during fall
and winter (Marchette & Smiley^8 , Hall et al. 1991,
Moser & Ross 1994, Rogers & Weber^9 ). Some
adults in the Altamaha River remain in freshwater
reaches after spawning, but extent of this fresh-
water use is not known. River temperatures that ex-
ceed 28–30° C during the summer create unsuitable
thermal conditions in most freshwater reaches.
During summer most adults and juveniles 1-year
old and older remain at the fresh/saltwater inter-
face in a few deep, cool water refuges (Hall et al.
1991, Flournoy etal.^10 ,Rogers & Weber4.9). These
southern populations seem to use fresh water env-
ronmentIessthan any populations known.
An exception to the previous pattern salt water
use by southern adults is found in the dammed San-
tee-Cooper River system. South Carolina, where
adults remain upstream of dams all year in fresh wa-
ter (e.g. one adult captured in 1984 at river km 190,
D. Cooke personal communication; 19 adults cap-97 000 cultured^5 shortnose sturgeon less than 9
weeks old from 1984 to 1992 (Smith et al. 1995).
Only 19% were tagged, so identification of wild and
cultured individuals is impossible. These fish ma-
lure at age 4–5, so stocking has already contributed
to the estimated total number of 1676 adults (T.
Smith personal communication). Stocking cultured
fish into the wild population may directly threaten
the long-term existence of the Savannah River pop-
ulation by disrupting the population's genetic adap-
tations to local environmental conditions (Waples
1991, Fleming 1994). Stocking cultured fish is not a
permanent solution to environmental or harvest
problems that cause low population abundance;
these problems still remain in the Savannah River.
Some of the stocked young have recruited to the
adult cohort, so abundance of adults has temporari-
ly increased. Because the estimate of adults in-
cludes wild and stocked fish, the Savannah River
population was not included in analyses of abun-
dance trends of the species.
Latitudinal pattern of anadromyCapture-tagging-recapture and telemetry studies of
adult shortnose sturgeon indicate a latitudinal pat-
tern in the amount of time spent in salt water.
Adults at the extreme northern part of the range
(northern rivers – Saint John, Androscoggin, and
Kennebec rivers. Maine; Table 1) use saline water
for all or most of the year (Dadswell 1979, Squiers el
al.^6 ,Squiers^7 ). Adults leave the estuary and forage
in Saint John River fresh water for only a few
months in spring and summer (e.g. June-August)
when river temperature is warmest. Some adults
overwinter in 30% seawater. Adults in less north-
erly rivers to the center of the range (north-central
rivers – Merrimack River, Massachusetts, to the(^8) Marchette, D.E. & R. Smiley. 1982. Biology and life history of
incidentally captured shortnose sturgeon. Acipenser breviros-
trum,in South Carolina. Report of South Carolina Wildl. Mar.
Res., Brunswick. 57 pp.
(^9) Rogers, S.G. & W. Weber. 1995. Movements of shortnose stu-
geon in the Altamaha River system. Georgia. Georgia Dept.
Nat. Resour., Contrib. 57. 78 pp.
(^10) Flournoy, P.H., S.G. Rogers & P.S. Crawford. 1992. Restoration
of shortnose sturgeon in the Altamaha River. Georgia. Georgia
Dept. Nat. Resour., Final Report to U.S. Fish & Wildl. Serv., At-
lanta. Proj. AFS-2. 54 pp.
(^6) Squiers, T.S., L.S Flagg. M. Smith. K. Sherman & D. Ricker.
- American shad enhancement and status of sturgeon stocks
in selected Maine waters. Maine Dept. Mar. Resour., Report to
Nat. Mar. Fish. Serv., Gloucester. pp. 20–64. 7
Squiers, T.S. 1982 Evaluation of the 1980–82 spawning run of
shortnose sturgeon (Acipenser brevirostrum) in the Androscog-
gin River, Maine. Maine Dept. Mar. Resour., Final Report to
Central Maine Power Co., Augusta. 15 pp.