Research Document - 2016/072

Status of Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) in the Saint John River, New Brunswick

By Bradford, R.G., Bentzen, P., Ceapa, C., Cook, A.M., Curry, A., LeBlanc, P. and Stokesbury, M.

Abstract

A recovery potential assessment of Atlantic Sturgeon was conducted by Fisheries and Oceans Canada (DFO) in January  2013 to provide information on the current status of the population, threats to its survival and recovery, habitat needs and feasibility of recovery. The Maritimes population unit occurring in the Saint John River (SJR) was designated threatened by the Committee of the Status of Endangered Wildlife in 2011. Abundance estimates derived from mark-recapture experiments indicate modest numbers of 1,000 to 3,000 spawners. Sex ratio, mean length, mean age and growth parameters were calculated for commercially caught fish. A mean estimate of effective population size (Ne = 110) indicates that the population is above the critical threshold (Ne = 50) for risk of inbreeding, but is very low for a population subjected to commercial exploitation. Age validation using Carbon-14 indicate pectoral fin spines underestimate sturgeon age in old fish. The primary threat to SJR sturgeon is the commercial fishery, which has been capped at 350 fish per year. Maintaining annual spawner abundances of approximately 1,000-3,000 adults in the lower Saint John River, while supporting a population with a broad body size and age distribution for both sexes, and improving upon the understanding of the genetic diversity within the population is proposed as a medium-term abundance recovery target. A potential distribution target would be that all life-history stages should be found in the Saint John River, with interannual appearances of multiple age classes within known marine foraging areas such as Minas Basin, Nova Scotia.

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