A population model for the Atlantic Sturgeon (Acipenser oxyrinchus) spawning population of the Saint John River, New Brunswick

Abstract

An assessment of Atlantic Sturgeon in the Saint John River (SJR), New Brunswick is presented. A two-sex age-structured model was developed using stock synthesis (SS3) software with data from the commercial landings from the SJR and Bay of Fundy (BoF). Sensitivity analyses explored various assumptions in the population model, including historical depletion in the early SJR fishery (late 19th century), selectivity of the SJR fishery, the magnitude of catches in the Bay of Fundy, sex ratio of catches, and steepness of the Beverton-Holt stock-recruit relationship. In most scenarios, the female Spawning Stock Biomass (SSB) was estimated to be above SSBMSY (the SSB at maximum sustainable yield) in 2020. Short-term (10-year) projections indicated that with the current Total Allowable Catch (TAC; 175 males and 175 females), the biomass would decline but remain above SSBMSY. Historical depletion since 1891 (three generations) are also presented for the purposes of Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessment (COSEWIC 2011). A separate analysis for the tagging data estimated fishing mortality since 2009 to be similar in trend and magnitude to those from the SS3 models.