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 National Marine Fisheries Service 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.  Because there is a need to understand whether reproduction is occurring in other rivers in the Chesapeake Bay, and if there is, to obtain an estimate of the size of the spawning population, we sampled the Pamunkey River, a tributary to the York River during the fall of 2013.  Numerous male sturgeon running milt and one spawned out female with residual eggs still present were captured.  The co-occurrence of reproductively active males and a recently spawned out female Atlantic sturgeon indicates that fall spawning occurs in the York River system.  We used a Schumacher-Eschmeyer formula for multiple census to determine the size of the spawning population.  The Schumacher-Eschmeyer model gave an estimate for the 2013 spawning population of 75 adult Atlantic sturgeon (95% CI = 17–168).  This study represents the first estimate of spawning population abundance for any river in the Chesapeake Bay DPS and only the third such estimate for Atlantic sturgeon range-wide.