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The Morone saxatilis (Striped Bass) population in Saint John River (SJR), NB, Canada, collapsed in the 1970s concurrent with dam construction, overfishing, and chemical pollution that may have impeded reproduction. To assess whether a chemical threat to Striped Bass or a health threat to fish consumers persists, we examined DDT and total mercury (THg) levels from 29 Striped Bass captured in the SJR including 16 genomically typed as SJR natives. DDT and DDD in female gonads were below detectable levels, and DDE averaged 0.08 ± 0.09 mg/kg wet weight (ww) but was considered too low to threaten reproduction. Total mercury in muscle and liver varied from 0.68 to 2.10 mg/kg and 0.35 to 3.27 mg/kg ww, respectively and exceeded Health Canada guidelines in all samples. We suggest regulators should update advisories for consumption including actively informing the public of the risk. [ABSTRACT FROM AUTHOR]

Barriers such as dams have been cited as a serious threat to striped bass survival, especially when they affect or impede migration and access to spawning grounds. On the Saint John River, New Brunswick, the installation of the large Mactaquac Dam in the immediate vicinity of a historic striped bass spawning location was suspected to have caused the arrest of striped bass reproduction and the collapse of the native striped bass population. In 2014, juvenile striped bass of confirmed Saint John River origin were documented in the river for the first time since 1979. In the current study, we examined juveniles from 6 years of sampling to determine corresponding years of successful recruitment. We also tracked adult striped bass matching the ancestry of native Saint John River juveniles to determine the timing and location of spawning. Over 5 years, we observed an annual upstream migration by adult striped bass to historic spawning areas near Fredericton, identified a dominant year class of Saint John River origin juveniles reproduced in 2013, and linked the apparent successful production of year classes to definable discharge conditions, that is, extended periods of sustained flow >36 hr downstream from the Mactaquac Dam. The results of this study suggest important first management actions towards recovering and sustaining the re‐discovered striped bass population in the Saint John River, New Brunswick. [ABSTRACT FROM AUTHOR]