Habitat Use during Early Life History Infers Recovery Needs for Shovelnose Sturgeon and Pallid Sturgeon in the Middle Mississippi River

Abstract

AbstractHabitat use by wild age‐0 shovelnose sturgeon Scaphirhynchus platorynchus and pallid sturgeon S. albus was quantified by trawling macrohabitats (i.e., main channel, main‐channel border, island, and artificial structures [e.g., wing dams]) in the middle Mississippi River during 1998–2007 (1,702 trawls; n = 1,507 age‐0 sturgeon captured). Age‐0 sturgeon catch rates were highest around artificial structures and island areas, while main‐channel habitat provided the lowest catch rates. Moreover, size‐selective macrohabitat analyses indicated that small age‐0 sturgeon (i.e., majority < 50 mm total length) were located in channel‐border dike and island side‐channel macrohabitats, while all other macrohabitats were occupied by small and large age‐0 sturgeon. Furthermore, our analyses indicated that age‐0 sturgeon mesohabitat use within macrohabitats was influenced by depth, substrate, and bottom velocity. Low velocity (i.e., ∼0.1 m/s), moderate depths (i.e., 2–5 m), and sand substrate were positively related to age‐0 sturgeon relative abundance. As such, instream habitat modifications that provide the correct combination of macrohabitats with suitable mesohabitats may hold high densities of age‐0 shovelnose sturgeon and pallid sturgeon and may improve recruitment success.