Lake sturgeon population trends in the St. Clair–Detroit River System, 2001–2019

Lake Sturgeon Acipenser fulvescens are listed as threatened or endangered in 15 states or provinces within their native range. Accordingly, investments in habitat and population restoration for this species have increased throughout the Great Lakes. To aide evaluation of restoration efficacy, robust population parameters are needed to inform management decisions. The St. Clair – Detroit River System (SCDRS) contains one of the largest self-sustaining Lake Sturgeon populations in the Great Lakes; however recent estimates of population abundance and growth parameters have not been assessed. Our study used baited setline and mark-recapture data collected between 2001 – 2019 to estimate whether the number of Lake Sturgeon captured varied annually and/or with water temperature and whether population abundance and population growth rate varied among three sub-populations located in the SCDRS. Trends in the number of Lake Sturgeon captured on setlines varied among sub-populations and by life stage. Annual trends in the number of Lake Sturgeon captured remained consistent over time in the upper St. Clair River, decreased for adults and increased for subadults in the lower St. Clair River, and increased in the Detroit River. With sub-population abundance of 20,184 (95% CI = 12,533 – 27,816) in the upper St. Clair River/southern Lake Huron, 6,523 (95% CI = 5,720 – 7,327) in the lower St. Clair River, and 6,416 (95% CI = 4,065 – 8,767) in the Detroit River, our study confirms that the SCDRS contains the largest Lake Sturgeon population with unimpeded access to the Great Lakes. The geometric mean population growth rate (λ) for all sub-populations indicated stable populations and ranged from 1.00 – 1.16. Our study provides an updated assessment of Lake Sturgeon population parameters that serve as a baseline to evaluate habitat restoration efforts and inform management of the SCDRS recreational Lake Sturgeon fishery.