Aaron D. Spares

The annual marine feeding aggregation of Atlantic sturgeon Acipenser oxyrinchus in the inner Bay of Fundy: population characteristics and movement

Atlantic sturgeon Acipenser oxyrinchus aggregate to feed from May to October in Minas Basin (45° N; 64° W), a large, cul-de-sac embayment of the inner Bay of Fundy. The aggregation consists mainly of migrants from the Saint John, NB and Kennebec Rivers, ME (99%). During 2004-2015, 4393 A. oxyrinchus were taken as by-catch by commercial fish trawlers or at intertidal fishing weirs, and 1453 were marked and/or sampled and released. Fork length (LF ) ranged from 458 to 2670 mm, but 72·5% were <1500 mm. Mass (M) ranged from 0·5 to 58·0 kg. The mass-length relationship for fish ≤50 kg was log10 M = 3·32log10 LF - 5·71. Observed growth of unsexed A. oxyrinchus recaptured after 1-8 years indicated fish of 90-179 cm LF grew c. 2-4 cm a year. Ages obtained from pectoral spines were from 4 to 54 years. The Von Bertalanffy growth model predicted K = 0·01 and L∞ = 5209 mm LF . Estimated annual mortality was 9·5-10·9%. Aggregation sizes in 2008 and 2013 were 8804 and 9244 individuals, respectively. Fish exhibited high fidelity for yearly return to Minas Basin and population estimates indicated the total at-sea number utilizing the Basin increased from c. 10 700 in 2010 to c. 37 500 in 2015. Abundance in the Basin was greatest along the north shore in spring and along the south shore in summer, suggesting clockwise movement following the residual current structure. Marked individuals were recaptured in other bays of the inner Bay of Fundy, north to Gaspé, Quebec, and south to New Jersey, U.S.A., with 26 recoveries from the Saint John River, NB, spawning run. Fish marked at other Canadian and U.S. sites were also recovered in Minas Basin. Since all A. oxyrinchus migrate into and out of the Basin annually they will be at risk of mortality if planned tidal power turbines are installed in Minas Passage.

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

AbstractThe 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 adu...