Empirical Evidence of Fall Spawning by Atlantic Sturgeon in the James River, Virginia

Abstract

Due to overfishing and habitat alteration, the anadromous Atlantic sturgeon Acipenser oxyrinchus oxyrinchus is severely depleted across its historic range. The James and York rivers in Virginia are the two rivers comprising the Chesapeake Bay distinct population segment, where Atlantic sturgeon reproduction has been confirmed. It is widely recognized that Atlantic sturgeon spawn in the spring throughout their range; however, there is debate over whether they also spawn in the fall. To determine if Atlantic sturgeon spawn in the fall, independent of the spring spawn, large‐mesh gill netting in the freshwater portion of the James River (above river kilometer 108) was conducted in the spring (April–June) and fall (August–October) for 3 years (2009–2011), resulting in the capture of 125 adult Atlantic sturgeon (three were recaptures) during the fall sampling, but none were captured during the spring. Field examination for sex and stage of maturity identified 106 mature males and one postspawned female. Sex was not determined for four fish, and due to time constraints, 11 were not examined. Forty mature males were externally tagged with Vemco© ultrasonic passives tags and movements were monitored with a Vemco© VR2W passive receiver array. Collection and tracking data showed that mature Atlantic sturgeon aggregate in the freshwater portion of the James River during the fall season, entering during August and out‐migrating by the end of November. No tagged fish were detected in the freshwater area of the river during the subsequent spring months. Though James River Atlantic sturgeon may spawn in the spring, we suggest there is strong evidence for an independent fall spawn, which should be considered in future management and recovery actions.

Evidence of natural reproduction of Atlantic sturgeon in the Connecticut River from unlikely sources

“…Natural reproduction in Atlantic Sturgeon populations is typically confirmed by documenting the presence of mature adults at spawning locales at spawning time [33] or by the presence of young life-stages (eggs and larvae) [34] or pre-migratory juveniles [15, 35]. Although neither spawning adults nor young life-stages have been observed in the Connecticut River for almost 100 hundred years, the carcass of a 2.13 M female specimen with immature eggs was observed 17 rkm from the river’s mouth in spring 2014 [36] suggesting that natural reproduction may have resumed in the river.…”

Atlantic sturgeon Acipenser oxyrinchus Mitchill, 1815 seasonal marine depth and temperature occupancy and movement in the Bay of Fundy

“…The Atlantic sturgeon Acipenser oxyrinchus Mitchill, 1815 is a large anadromous benthic‐feeding fish that occurs along the east coasts of North and South America from French Giana to Labrador and formerly northern Europe (Dadswell, ). They spawn in freshwater habitat during summer, or autumn (Balazik, Garman, Van Enennam, Mohler, & Woods, ; Van Eenennaam & Doroshov, ), remain in estuaries until about 5–10 years of age and 100 cm fork length (FL), and then migrate to sea (Dadswell, ). Depending on their sex and the latitude of their natal river, Atlantic sturgeon mature at different ages and sizes.…”

Stock Origins of Subadult and Adult Atlantic Sturgeon, Acipenser oxyrinchus, in a Non-natal Estuary, Long Island Sound

“…Notable was the first finding of numerous young-of-the-year specimens in the Delaware River in 2009 (Fisher 2009), proof that successful natural reproduction had occurred there. Similarly, the population of the James River, VA, was believed with up to 99 % probability to be extirpated (Grogan and Boreman 1998), but may have recently rebounded to more viable levels (Balazik et al 2012). However, Atlantic sturgeon was listed in April 2012 for protection under the U.S.…”