Discovery of a New Spawning Population of Atlantic Sturgeon Acipenser oxyrinchus in the Pamunkey River, Virginia with an Estimate of the Annual Spawning Run Size

The NMFS listed five distinct population segments of Atlantic sturgeon as threatened and endangered under the Endangered Species Act on February 6, 2012.  At that time, the only known spawning population of sturgeon in the Chesapeake Bay was in the James River, though antidotal evidence suggested that spawning may be occurring in the Pamunkey River.  In 2013, numerous male sturgeon running milt and one spawned out female were captured and in 2014, over 100 adults were captured.  A Schumacher-Eschmeyer model was used to determine the size of the spawning run in both years, it estimated a population of 75 adults (95% CI = 17–168) in 2013 and 151 (95% CI, 89–213) in 2014.  We also analyzed the effective population size of the population based on 18 genetic samples in 2013 and a total of 72 genetic samples after the 2014 season.  Regardless of sample size, the effective population size of the Atlantic sturgeon in the Pamunkey River is only approximately 10 to 11 individuals.  These spawning run estimates are the first estimates of abundance of any life stage for any river in the Chesapeake Bay DPS and only the third such estimate for Atlantic sturgeon range-wide.