2007 Status Review of Atlantic sturgeon - National Marine Fisheries ...

unpublished reports indicate that most, if not all, subpopulations are statistically different (P <
0.05) based on allelic/haplotype frequencies, AMOVA, and FST (and mtDNA equivalent)
statistical tests using both mtDNA and nDNA genetic markers (Table 3, 4, and 5; Figure 16, 17,
and 18). King also increased the number of loci used in his nDNA analysis from seven to 12, to
help identify the genetic relatedness between Atlantic sturgeon subpopulations with greater
certainty. 20 The use of 12 microsatellite markers resulted in an average accuracy of 88% for
determining a sturgeon’s natal origin and an average accuracy of 94% for correctly classifying it
to a DPS determined by the SRT (Table 6). These results are an improvement to earlier findings
using only 7 microsatellite markers and resulted in a 12% (~9 percentage points) increase in
natal origin classification rates and 8% (~6percentage points) increase in DPS classification rates
(Table 6). However, tissue samples from YOY and adults are limited to 12 subpopulations; thus,
the SRT also evaluated subadults in some cases (18). There were no major differences observed
between the two genetic tree analyses that included or excluded subadults. As a result of the
high classification success rate using nDNA microsatellites and similar findings using mtDNA,
the SRT concluded that nDNA analysis would be used for the remainder of the DPS analysis.
Markedly Separated Based on Physiological or Behavioral Factors
Though the genetic markers used to differentiate among the subpopulations examined were not
linked to specific traits (mtDNA d-loop region and nDNA microsatellites), it is assumed that
these genetic markers indicate differences in physiological, ecological, or behavioral factors as
the level of genetic differentiation between subpopulations is high (Vannote et al. 1980,
MacLean and Evans 1981, Avise 1992, Nielsen 1998). Some potential physiological or
behavioral factors that are unique to Atlantic sturgeon are related to spawning conditions. The
majority of southern subpopulations (specifically the Cape Fear, Pee Dee, ACE Basin, Savannah,
Congaree, and Altamaha rivers) have been documented to participate in a fall spawning run, as
well as a spring run (Collins et al. 2000a, D. Peterson, UGA, Pers. Comm. 2006). It is unknown
why a fall run may be beneficial for Atlantic sturgeon, although many salmonids exhibit similar
characteristics (NRC 1996). Benefits may include reduced competition or avoidance of
unfavorable environmental conditions (e.g., low DO) occurring during the summer months.
Differences in the innate dispersal patterns of sturgeon species in early life stages also suggest
that there are markedly separated differences in behavior between subpopulations of sturgeon (B.
Kyndard, CAFL, Pers. Comm. 2006). Boyd Kynard (USGS), a researcher at Conte Anadromous
Fish Laboratory (Turner Falls, Massachusetts), has noted major differences in innate dispersal
patterns of early life stage sturgeon species including Acipenser fulvescens (Wolf and
Menominee rivers), A. brevirostrum (Connecticut and Savannah rivers), A. transmontanus
(Sacremento and Kootenai rivers), and Atlantic/Gulf sturgeon subpopulations (Hudson and
Suwannee rivers). This research suggests that Atlantic sturgeon are likely adapted to unique
features of their watershed, considering their genetic discreteness and differing migration
behaviors. These findings are similar to research conducted on striped bass (Morone saxatilis),
an anadromous fish like Atlantic sturgeon, which correlated egg characteristics (egg diameter,
egg density, etc.) with watershed type (i.e., low, medium, high energy) (Bergey et al. 2003).
Differences in egg characteristics likely are the result of subpopulation adaptations to the
20
Only seven populations were analyzed using 12 loci: Kennebec, Hudson, James, Albemarle, Savannah, Ogeechee,
and Altamaha rivers.
27