Impacts of life history and biogeography on the genetic stock structure of Atlantic sturgeon Acipenser oxyrinchus oxyrinchus, Gulf sturgeon A. oxyrinchus desotoi, and shortnose sturgeon A. brevirostrum

Waldman, J.R.; Grunwald, C.; Stabile, J.; Wirgin, I.

Journal of Applied Ichthyology 18(4/6): 509-518

2002


ISSN/ISBN: 0175-8659
DOI: 10.1046/j.1439-0426.2002.00361.x
Accession: 003805188

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Abstract
Non-genetic data indicate that Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) are substantially dispersive in marine waters, possibly remaining out of their natal rivers for many years at a time. Gulf sturgeon (A. o. desotoi) only appear to use marine waters during cooler months, summering in rivers. Shortnose sturgeon (A. brevirostrum) are highly residential in rivers, but do sometimes go to sea and move between rivers. We used the polymerase chain reaction (PCR) and direct sequence analysis of a portion of the mitochondrial DNA (mtDNA) control region to examine stock structure, haplotypic diversity, and gene flow (Nfm ) among these taxa, hypothesizing that gene flow would be highest in Atlantic sturgeon. Stock structuring was strong within all three taxa - most river populations supported genetically distinct stocks of sturgeons. Estimates of gene flow among regions were low to moderate in comparison with other anadromous fishes, suggesting that homing fidelity within all three taxa is high. However, average gene flow in Atlantic sturgeon was almost three times higher than in shortnose sturgeon, which somewhat exceeded gene flow values for Gulf sturgeon. Levels and patterns of haplotype diversity differed dramatically between the largely-sympatric Atlantic and shortnose sturgeon. Atlantic sturgeon exhibited a cline in haplotype diversity with monomorphism or very low diversity observed in northern, previously glaciated populations and moderate to high levels of diversity in southern, non-glaciated populations. In contrast, no difference in haplotype diversity and little sharing ofhaplotypes was observed between northern and southern populations of shortnose sturgeon. We hypothesize that the greater mtDNA diversity in northern populations of shortnose sturgeon resulted from their use of a glacial refugium that was not occupied by Atlantic sturgeon. Gulf sturgeon show much lower gene flow than Atlantic sturgeon. This may be due to their more temporally and geographically constrained marine migrations, which may reduce the opportunities for straying, and a need to return to assured summer thermal refugia. A new finding is the probable existence of a native, genetically-distinct Atlantic sturgeon stock in the James River, which has ramifications for restoration strategies for the species in Chesapeake Bay.