Age and Growth of Atlantic Sturgeon from the Saint John River, New Brunswick, Canada

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AbstractAs a long‐lived and late‐maturing species, Atlantic Sturgeon Acipenser oxyrinchus are susceptible to overharvest, which makes knowledge concerning their age and growth essential to sustainable management. The Saint John River, New Brunswick, and the St. Lawrence River, Quebec, support the two remaining commercial fisheries for Atlantic Sturgeon in North America; however, the relationship between age and growth has not previously been modeled for the Saint John River population. Ages of Saint John River Atlantic Sturgeon were estimated by using pectoral fin spine sections collected from 262 individuals of known TL. Most (87%) of the pectoral spine sections were aged by two readers to evaluate possible reader bias. An age–bias plot and coefficient of variation (CV) indicated relatively low between‐reader precision (CV = 5.6%) compared with that reported in other studies. Von Bertalanffy growth model (VBGM) parameters were estimated for males (n = 67), females (n = 85), and the combined sexes. Unsexed juveniles and subadults smaller than 150 cm TL (n = 110) were used for the lower part of each curve. The growth models indicated that (1) males reached maximum length sooner than females and (2) females continued to grow more as adults to greater lengths (males: Brody growth coefficient K = 0.06, asymptotic length L∞ = 230 cm TL; females: K = 0.04, L∞ = 264 cm TL). As predicted, the VBGM parameters estimated for combined sexes of the Saint John River stock (K = 0.05, L∞ = 254 cm) were intermediate to those of Atlantic Sturgeon from the Hudson and St. Lawrence rivers, in agreement with a previously observed latitudinal trend in growth.Received June 26, 2014; accepted January 13, 2015