EPA's Vessel General Permit and Small Vessel General

this population is about 9,500 fish (Squiers 2003), suggesting the population has increased by
about 30% in about a twenty year period.
Data from the Delaware River suggest that the population may be stable. Brundage and
O’Herron (2006) estimate that the current population for the Delaware River is 12,047 adult fish
(1999-2003; 95% CI: 10,757-13,589), which is similar to the 1981/84 estimate by Hastings et
al., (1987) of 12,796 fish (95% CI: 10,288-16367). The recent capture of several fish that were
tagged as adults by Hastings et al., (1987) suggests that older fish may comprise a substantial
portion of the Delaware River population. Based on studies from other sturgeon species we know
of no evidence of senescence in sturgeon and we would expect that these fish are reproductively
active (Paragamian et al. 2005). Despite their longevity, the viability of sturgeon populations is
sensitive to variability in juvenile recruitment and survival (Anders et al. 2002, Gross et al. 2002,
Secor et al. 2002). Although interannual variation in juvenile recruitment would be expected as a
result of stochastic factors that influence spawning and egg/larval survival, if the mean
population size does not change over the long-term it then it would appear there is sufficient
juvenile survival to provide at least periodic recruitment into the adult age classes. Data on
juvenile recruitment or age-1+ survival would, however, establish whether this population is at a
stable equilibrium.
South of Chesapeake Bay, populations are relatively small compared to their northern
counterparts. The largest of the southern populations of shortnose sturgeon is the Altamaha River
population. Population estimates have been calculated several times for sturgeon in the Altamaha
since 1993. Total population estimates shown pretty sizeable interannual variation is occurring;
estimates have ranged from as low as 468 fish in 1993 to over 6,300 fish in 2006 (NMFS 1998a,
DeVries 2006). The Ogeechee River is the next most studied river south of Chesapeake Bay and
abundance estimates indicate that the shortnose sturgeon population in this river is considerably
smaller than that in the Altamaha River. The highest point estimate in 1993 using a modified
Schnabel technique resulted in a total population estimate of 361 shortnose sturgeon (95% CI:
326-400). In contrast the most recent survey resulted in an estimate of 147 shortnose sturgeon
(95% CI: 104-249), suggesting that the population may be declining.
Throughout the species range there are other extant populations, or at least evidence that several
other basins are used periodically. Shortnose sturgeon have been documented in the St. Johns
River (FL), the St. Mary’s River, Chesapeake Bay, Potomac River, Piscataqua River, the
Housatonic River and others. Some basins probably previously contained shortnose populations,
but recent sampling has been largely unsuccessful. Despite the occasional observations of
shortnose sturgeon, populations may be extinct in several basins (e.g., St. John’s (FL), St.
Mary’s, Potomac, Housatonic and Neuse rivers). Those few fish that have been observed in these
basins are generally presumed to be immigrants from neighboring basins. In some cases, (e.g.
Chesapeake Bay) migratory information collected from tagged fish and genetic evidence
confirms that fish captured in Chesapeake Bay were part of the Delaware River population
(Grunwald et al. 2002, Wirgin et al. 2005).
Threats
Natural Threats. Yellow perch, sharks and seals are predators of shortnose sturgeon juveniles
(NMFS 1998a). The effects of disease and parasites are generally unknown.
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