Connectivity Of Large-River Networks Is Important Throughout Fish Life History

Understanding life history requirements is important for conservation of the 60 out of 68 large river specialist fishes imperiled in the Mississippi River Basin.  We sought to elucidate movements of two large river specialist fishes, shovelnose sturgeon and blue sucker, between the Wisconsin and Mississippi rivers prior to operation of the Prairie Du Sac Dam fish elevator on the Wisconsin River.  Our study used a combination of hard part (fin ray and otolith) microchemistry, muscle stable isotope (¹⁴C, ¹⁵N) chemistry, and mark-recapture data to determine when shovelnose sturgeon and blue sucker use these rivers as habitats throughout life history.  Our analyses provide evidence that these fish species use the Wisconsin and Mississippi Rivers throughout life and that these connections are particularly important during early life.  For example, while field collection data show the focal species spawn in the Wisconsin River, hard part microchemistry suggests that the Mississippi River can provide critical early life history habitat.  The apparent need for connections in this system underscores the importance of maintaining and restoring connections between large mainstem rivers and their tributaries.