Population Characteristics of Adult Atlantic Sturgeon Captured by the Commercial Fishery in the Saint John River Estuary, New Brunswick

The commercial fishery for Atlantic Sturgeon Acipenser oxyrinchus in the Saint John River, New Brunswick, began in 1880. The early fishery was unregulated, and the adult stock was depleted by 1886 after landings of 712 metric tons. After a 10‐year closure the fishery was reopened in 1897 with management regulations, and landings varied from 6 to 20 metric tons/year until 2010. In 2011 an annual quota of 350 adults was established and landings are now stable at 11.3 ± 1.7 (mean ± SD) metric tons/year. Since 2009, fishers have collected biological statistics from adults taken in the fishery and 14–60% of captured individuals have been marked and released each year. During 2009–2015, annual mean values of total length and dressed weight of landed adults were stable, the male : female sex ratio was 1.2:1.0, and mean age of males and females was 27.2 and 34.0 years, respectively. Estimates of instantaneous total mortality ranged from 0.08 to 0.11, and mean annual survival was 90.9%. Of 1,396 marked adults released, 147 were recaptured in the estuary in subsequent years. Tag returns indicated that the modal spawning periodicity of males was 2 years and that of females was 4 years. Valid, modified Schnabel and Jolly–Seber mean annual population estimates for 2013–2015 were 18,179 and 20,798 adults, respectively. The quota in relation to these estimated adult populations represented annual exploitation rates of 1.9% and 1.7%, which are below F50 and would maintain present stock size. The virgin adult population was determined using 1880–1886 total landings and a mean weight range for adults of 50–30 kg. Estimated range of the 1880 virgin population size was 14,240–23,733 adults. These data suggest that the fishery is sustainable at its current annual yield and that the population is near the carrying capacity of the Saint John River. Received July 12, 2016; accepted November 17, 2016 Published online February 21, 2017