Populations of Atlantic sturgeon Acipenser oxyrinchus are at historically low levels along the Atlantic coast of North America. Atlantic sturgeon is a long-lived species with a complex life history, making population assessment difficult. The purpose of this study was to determine seasonal habitat use by juvenile Atlantic sturgeon in the Hudson River estuary and provide recommendations for future population monitoring. Our study focused on Newburgh and Haverstraw bays in the Hudson River, as these are areas of known juvenile sturgeon concentrations. The habitat within each bay was coarsely stratified according to substrate (hard versus soft) and depth (deep versus shallow). Sampling occurred during fall 2003, spring and fall 2004, and spring and fall 2005. Fall sampling occurred from October through November and spring sampling occurred from March through April. We used anchored gill nets of 76-, 102-, and 127-mm stretch mesh fished together at a sampling site. A total of 562 individual juvenile Atlantic sturgeon were captured during the course of this study (14 were captured more than once), the majority (90%) coming from Haverstraw Bay. Soft and deep habitat comprised only 25% of the available habitat in Haverstraw Bay but yielded the greatest frequency of catches, the highest mean catch per unit effort (CPUE), and lowest variance of CPUE. Catch per unit effort was highest during spring seasons in soft-deep areas of Haverstraw Bay. These results suggest that future population monitoring should focus sampling effort in soft-deep areas of Haverstraw Bay to have the greatest statistical power in detecting population trends.

Accurate estimates of age and growth of fishes are important in the management and conservation of species and for the development of modeling approaches. Assessments of endangered or rare species typically are limited by poor or inadequate data owing to low abundance, unrepresentative sampling, and/or restrictions on sampling. Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus, which occurs along the east coast of North America, has five distinct population segments (DPSs) listed under the U.S. Endangered Species Act. The New York Bight (NYB) DPS is listed as endangered and represents the largest DPS in the United States. Coastal trawl surveys from 2005 to 2012 were used to evaluate the current age structure of the NYB DPS. A total of 21 year‐classes (mean age = 8.89 years, n = 742 fish) were observed. Age data for the NYB DPS were combined with other available age estimates from multiple research laboratories and sources (n = 2,774) in the Hudson River and Delaware River as well from the coastal regions of New York, New Jersey, and Delaware from 1975 to 2012. Collectively, the combined data set captured much of the age range of the species, minimizing age biases and resulting in improved von Bertalanffy parameter estimates (L∞ = 278.87, K = 0.057, t0 = −1.27) with high overall model fit (r2 = 0.87). We assessed the effects of individual data sets through a series of leave‐one‐out bootstrap routines that evaluated the influence of each data set on growth parameter estimates. The parameter estimates of the von Bertalanffy growth function were influenced by sampling location and/or researcher effects. Despite these differences, the combined data set approach used here represents the most comprehensive study on the age‐and‐growth relationship of Atlantic Sturgeon and provides parameter estimates for the development of population dynamics models and valuable information for future management. Received February 23, 2015; accepted September 24, 2015

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The 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.