Atlantic Sturgeon Annual Spawning Run Estimate in the Pamunkey River, Virginia

On February 6, 2012, the National Marine Fisheries Service listed five distinct population segments (DPSs) of Atlantic Sturgeon Acipenser oxyrinchus encompassing their entire U.S. range, including one DPS in Chesapeake Bay, as either threatened or endangered under the Endangered Species Act. Designation of DPSs is a management tool that identifies significant, discrete, geographically defined portions of a species' range, which can be listed as unique management units. At the time of listing, all DPSs except the Chesapeake Bay DPS comprised several rivers with known reproduction. After the Chesapeake Bay DPS was established, an additional spawning population was confirmed in the Pamunkey River, which is part of the York River system. We used the Schumacher-Eschmeyer formula for multiple census to estimate the number of adult Atlantic Sturgeon that spawned in the Pamunkey River during 2013. Gill nets were placed between river kilometers 27 and 67 in the upper Pamunkey River for 10 weeks during spawning season. The Schumacher-Eschmeyer model gave an estimate of 75 adult Atlantic Sturgeon (95% confidence interval = 17-168 adults) for the 2013 spawning population. This study represents the first estimate of annual spawning population abundance for any river in the Chesapeake Bay DPS and is only the third estimate of Atlantic Sturgeon abundance rangewide.