Age and Growth of Juvenile Atlantic Sturgeon in the Lower Hudson River

Abstract

AbstractThe precipitous decline of Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus coupled with their recent listing under the U.S. Endangered Species Act necessitates investigations into their population dynamics. Our objectives were to (1) estimate age of juvenile Atlantic Sturgeon by using pectoral spine sections; (2) determine annual growth periodicity in hatchery‐reared and recaptured wild Atlantic Sturgeon to validate our aging method; (3) determine growth rates for recaptured juveniles; and (4) back‐calculate lengths from ages estimated by using pectoral spine sections from captured juveniles. Fish were captured via gillnetting in Newburgh and Haverstraw bays, Hudson River, during fall 2003, spring and fall 2004, and spring and fall 2005. Two readers agreed upon 91% (n = 474) of ages estimated for juvenile Atlantic Sturgeon, establishing a coefficient of variation of 1.7%. Eight year‐classes (ages 1–8) were represented, with age‐4 fish making up the largest age‐class (39%; n = 203) and age‐1 fish being the least represented (<1%; n = 4). Multi‐annual oxytetracycline injections in four cohorts of hatchery‐reared Atlantic Sturgeon (n = 34) demonstrated a two‐part zone for each year of growth, as did four recaptured juveniles that were at liberty for a least 1 year, which exhibited mean growth rates of 0.3 mm/d and 2.4 g/d. We back‐calculated median FLs from annulus positioning in ages 2–8 by using dorsal and ventral lobes of pectoral spine sections and compared the results to actual reported lengths. Dorsal and ventral lobes underestimated the median FLs of all age‐classes except ages 3 and 7, for which lengths were overestimated. We found statistical differences between dorsal‐ and ventral‐derived median FLs, suggesting that both regions must be evaluated. Our overall goal is to provide researchers with a baseline of age and growth data for future work on juvenile Atlantic Sturgeon.