Evaluating the Environmental Parameters Associated with Spawning Movement of Gulf Sturgeon (Acipenser desotoi) in the Bouie River

Gulf sturgeon are federally listed as “threatened” and are native to seven rivers along the northern Gulf of Mexico. Populations natal to the Pascagoula River have one verified spawning reach in the lower Bouie River, near Hattiesburg, MS. This reach is modified by four aggregate mining areas, referred to as pits. Researchers observed post-spawn Gulf sturgeon over-summering in pits rather than migrating to downstream holding areas in the Pascagoula River. We leverage acoustic telemetry and environmental data to assess drivers of arrival and departure from the Bouie River, describe vertical stratification in the water column in pits, and compare pit temperatures to those in holding areas. Generalized mixed linear modeling demonstrated that arrival was associated with lower discharge rates, whereas departure was associated with higher surface water temperatures and greater daily temperature extremes. Sturgeon had varying occupancy rates in pits, with four over-summering events over 3 years. Stratification formed in the pits in May and persisted through October, with bottom and middle strata exhibiting cooler temperatures than holding habitats. Cooler bottom temperatures indicate potential for thermal refuge in the pits. However, persistent stratification leads to low dissolved oxygen in bottom waters, warranting further research into the environmental stressors of this system.