Status of Atlantic Sturgeon of the Hudson River Estuary, New York, USA
Andrew W. Kahnle, Kathryn A. Hattala, and Kim A. McKown
Abstract.—Commercial harvest of Atlantic sturgeon Acipenser oxyrinchus from the Hudson River Estuary peaked in the late 1800s, declined precipitously soon after, and remained at low levels until the late 1970s when a resurgence in the fishery occurred. Preliminary analysis of the fishery suggested that the harvest was not sustainable. The state of New York banned possession of Atlantic sturgeon in 1996. A coastwide ban followed in 1998. We examined available data to determine whether the closures of the 1990s were warranted and to track stock recovery since the closure. We used an eggper-recruit model to determine an acceptable fishing rate (F50%). We assumed a maximum age of 60 and a natural mortality rate M of 0.07 and obtained an F50% of 0.03. The fishing rates F estimated during the recent fishery were 0.33 for males and 0.17 for females, well over the F50%. We set an abundance target for spawning females at 3,000 animals, which was 50% of the estimated maximum abundance in the late 1800s. We estimated mean annual spawning stock size during the fishery as mean annual harvest divided by exploitation rate. Estimated numbers of mature fish were approximately 600 males and 270 females (less than 10% of the abundance threshold). Our estimates of fishing rate and female stock size suggest that the stock was severely overfished prior to and during the recent fishery. We used changes in relative abundance of juveniles to infer changes in recruitment. Relative estuarine abundance of premigrant juveniles declined in the late 1970s in the bycatch of the American shad Alosa sapidissima commercial gill-net fishery and in the mid-1980s in a 3-m bottom trawl survey. Both in-river indices suggest a slight improvement since the late 1990s. Relative abundance of postmigrant juveniles in a bottom trawl survey off the coast of northern New Jersey declined from the late 1980s through the present.