Age, growth and recruitment of Hudson River shortnose sturgeon (Acipenser brevirostrum)

Shortnose sturgeon (Acipenser brevirostrum), an Endangered Species, has experienced a several-fold increase in abundance in the Hudson River in recent decades. Age structure and growth were investigated to evaluate the hypothesis that improvements in water quality during the late 1970s stimulated population recovery. Specimens were captured using gill nets bi-monthly 2003 to 2004. Annuli in fin spine sections were determined to form at an annual rate and yielded age estimates of 5--30 years for sizes 49--105cm Total Length (n = 554). Hindcast year-class strengths, corrected for gill net mesh selectivity and cumulative mortality indicated high recruitments (28,000--43,000 yearlings) during 1986--1992, which were preceded and succeeded by c. 5 year-periods of lower recruitment (5,000--15,000 yearlings). Results indicated that Hudson River shortnose sturgeon abundance increased due to the formation of several strong year-classes occurring about five years subsequent to improved water quality in important nursery and forage habitats in the upper Hudson River estuary.