have a broad niche breadth; thus, the species should
be capable of occupying a wide geographic range,
many habitats, and producing large populations
(Brown 1984). The great individual variability for
foraging has likely contributed to the extraordinary
persistence of shortnose sturgeon during the many
habitat changes they have experienced during their
long existence.locationoffirstdam(km)Figure 3. Relationship in 10 populations between the maximum Spawning migration and impact of dams
upstream spawning location of shortnose sturgeon and location
of the first (lowermost) dam A 1:1 relationship of spawning loca- Spawning site locations in three unobstructed rivers
tion to dam location is indicated by the 45° line. and two rivers with the first dam located more than
240 km upstream provide information on the nat-
deep water channel habitat within or directly down- ural pattern of shortnose sturgeon migratory dis-
stream of the summer range. No telemetered juve- tance. The maximum upstream spawning site loca-
nile or adult tracked in the Connecticut River ever tion of fish in unobstructed rivers is river km 220-
used the Holyoke Dam reservoir area except when 225 in the Delaware River. river km 275-278 in the
moving up-or downstream to areas of use. Savannah River. and river km 210-220 in the Alta-
In estuarine environments, most juveniles and maha River. This indicates a common pattern of mi-
adults forage together in the fresh/saltwater inter- grating upstream to about river km 200 or farther
face where salinity is variable, substrate is usually (Hall et al. 1991. O’Herron et al. 1993, Rogers &
mud and sand, and vegetation is often present. Weber^9 , Collins & Smith 1996). Some Savannah
Adults in the Saint John estuary foraged over sand/ River fish stopped at river km 179-190, but even
mud ormud substrate with emergent macrophyte these fish migrated almost to river km 200. Also,
vegetation in 5-10 m depths in summer and over- some Altamaha River migrants stopped at river km
wintered in the lower estuary in deep water with 50 - 125, the lowermost potential spawning location
mud substrate. Kennebec and Androscoggin river found in any unobstructed river. If these fish
adults foraged on tidal mud flats with patchy macro- spawned, then there is more variation for spawning
phyte vegetation and18-25 ppt salinity (McCleave location in the Altamaha River than elsewhere in
et al. 1977). or in shallow or deep tidal channels with the species’ range. Because this pattern is not sup-
salinity of 0-21 ppt that often had vegetation ported by observations from other rivers, and
(Squiers et a].^6 ). Adults overwintered in deep water spawning was not verified, the Altamaha River mi-
in the lower estuary (Squires et al.^7 ). Pee Dee River grants need further study. In addition, adults in the
adults foragedinthe fresh/saltwater interface (0.5-1 Hudson River spawn near Troy Dam (river km 246,
ppt salinity) during spring and summer. then over- Dovel et al. 1992). Pee Dee River adults likely
wintered downstream in the lower estuary in 15 ppt spawn in the reach downstream of Blewett Falls
salinity (Dadswell et al. 1984). A similar pattern was Dam at river km 298 (Ross et al. l988), although
found in the Savannah River (Hall et al. 1991). but some spawned at river km 192 (Marchette& Smi-
not in the Altamaha River. where fish occur less in ley^8 ) similar to the pattern observed in the Savan-
high salinity water (Flournoy et al.^10 , Rogers & nah River. Thus, all adults in four rivers (two north-
Weber^9 ). central and two southern) migrate to about river km
All telemetry studies of foraging behavior of ju- 200 or farther to spawn. No data were collected
veniles and adults cited previously and diet studies from the far northern rivers because all have dams
cited in Dadswell et al. (1984) found much individu- in the lower river that block upstream migration.
al variability. This suggests that shortnose sturgeon Saint John River adults may spawn in the reach be-