Lake Sturgeon population trends in the St. Clair-Detroit River system, 2001-2019

ObjectiveThe Lake Sturgeon Acipenser fulvescens is listed as threatened or endangered in 15 states or provinces within the species' native range. Accordingly, investments in habitat and population restoration for this species have increased throughout the Great Lakes. To aid in the 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.MethodsOur study used baited setline and mark-recapture data collected between 2001 and 2019 to estimate whether the number of Lake Sturgeon captured varied annually and/or with water temperature and whether population abundance and the population growth rate (lambda) varied among three subpopulations located in the SCDRS.ResultTrends in the number of Lake Sturgeon captured on setlines varied among subpopulations 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 subpopulation abundances of 20,184 (95% confidence interval [CI] = 12,533-27,816) in the upper St. Clair River/southern Lake Huron, 6523 (95% CI = 5720-7327) in the lower St. Clair River, and 6416 (95% CI = 4065-8767) 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 lambda for all subpopulations indicated stable populations and ranged from 1.00 to 1.16.ConclusionOur study provides an updated assessment of Lake Sturgeon population parameters that serve as a baseline to evaluate habitat restoration efforts and to inform management of the SCDRS recreational Lake Sturgeon fishery. Lake Sturgeon are a threatened or endangered fish species throughout much of their native range. The sturgeon population in the St. Clair-Detroit River system is one of the largest in the Great Lakes with nearly 30,000 individuals and is in stable condition.Impact statement