Genetic Analyses of Striped Bass in the Chesapeake Bay: an Investigation of Connectivity Among Virginia Subestuaries and an Evaluation of Close-Kinship Mark Recapture Methodology to Estimate Spawning Abundance.
Master of Science (M.Sc.)
Virginia Institute of Marine Science
John E Graves
Jan R McDowell
John M Hoenig
Mark J Brush
The striped bass (Morone saxatilis) is an anadromous fish distributed along the eastern coast of North America that currently supports one of the most lucrative and important commercial and recreational fisheries in the region. Since the recovery of the Atlantic stock after a collapse in the late 1970s, studies have focused on understanding the connectivity of major spawning grounds and improving methods of abundance estimation. Studies support strong site fidelity of striped bass to major estuaries along the Atlantic coast, but there has been disagreement about connectivity within the largest spawning ground, the Chesapeake Bay. Additionally, no estimates exist for striped bass abundance within the Chesapeake Bay. The objectives of my thesis were to examine the fine scale genetic population structure of striped bass within the lower Chesapeake Bay, and to test the feasibility of a novel, fishery-independent molecular methodology, close-kinship mark-recapture analysis (CKMR), to estimate spawning adult abundance within the Rappahannock River. Sampling of 1,132 adult striped bass and 389 young-of-year (YOY) striped bass was done during the 2016 and 2017 spawning seasons on major spawning grounds of the James, Mattaponi, and Rappahannock rivers. Twenty microsatellite loci were used to examine both the spatial genetic heterogeneity among the river systems and the temporal heterogeneity between sampling years within a river. Significant population pairwise FST values were recovered from 18 of the 21 pairwise comparisons. However, mean FST values between temporal comparisons were higher than those among spatial comparisons, suggesting a lack of biologically meaningful population structure among rivers. Additional analyses and a 30-year tagging data set also support a rate of connectivity among the major rivers high enough to maintain similar allele frequencies. Combined, the data support one genetic stock of striped bass within the lower Chesapeake Bay. The same suite of markers was then used to test the feasibility of CKMR to estimate adult abundance of striped bass within the Rappahannock River system. Using existing sampling programs, 371 spawning adults and 389 YOY were collected on the spawning and nursey grounds of the Rappahannock River in 2016. These samples yielded 2 parent-offspring pairs, resulting in an abundance estimate of 145,081 adult spawning striped bass. Additional analyses indicated that a relatively precise estimate (recovery of 50 POPs) would be made if sample sizes totaled 850 adults and 850 YOY. CKMR can be a feasible option of abundance estimation for striped bass. Overall, my study has provided the first estimate of abundance for Chesapeake Bay striped bass, and has provided strong support of a single, spawning stock of striped bass within the Chesapeake Bay.
© The Author
Michaelsen, Savannah, "Genetic Analyses of Striped Bass in the Chesapeake Bay: an Investigation of Connectivity Among Virginia Subestuaries and an Evaluation of Close-Kinship Mark Recapture Methodology to Estimate Spawning Abundance." (2018). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1550153637.