Variability in estuarine habitat use of a threatened species in the northern Gulf of Mexico: implications for coastal restoration

Coastal restoration projects often require sediment resources borrowed from estuarine or marine ecosystems. A generalized additive modeling (GAM) framework was used to characterize fish-habitat relationships and predict spatiotemporal and ontogenetic shifts of Gulf sturgeon distri-bution within an impacted estuary in the northern Gulf of Mexico, Lake Pontchartrain. Habitat use and movement of Gulf sturgeon (n = 103) was monitored using an array of acoustic receivers (n = 81) from 2016 to 2019. Telemetry data was paired with environmental conditions hindcast from a high-resolution hydrodynamic model to develop GAMs for three life stages of Gulf stur-geon: juvenile, sub-adult, and adult. Model results demonstrated clear spatial, temporal, and ontogenetic shifts in habitat use for Gulf sturgeon in the Lake Pontchartrain estuary. The importance of spatial and temporal variables in the final models of all life stages suggests that distribution of Gulf sturgeon within the estuary is more likely driven by biology (prey distribu-tion) rather than environment. Interestingly, dependence of Gulf sturgeon on the estuary for overwintering habitat declined with ontogeny. The northeastern shoreline of Lake Pontchartrain was identified as potential nursery habitat for overwintering juvenile sturgeon from the Pearl River, while eastern portions of the estuary and associated channels provide critical staging habitat and corridors of connectivity for migrating sub-adult and adult sturgeon. Given the clear need to prioritize conservation of Gulf sturgeon while restoring coastal marshes, findings from this study provide needed information to shape future coastal restoration and inform the siting and timing of future dredging operations in Lake Pontchartrain.