Role of Hydrology on the Distribution and Population Structure of Sauger in Lower Missouri River

Many temperate large rivers are channelized with flow regulated by dams.  Aquatic habitats in lower Missouri River (LMOR; USA) are undergoing restoration to mitigate loss during channelization, but flows are regulated to address congressionally authorized purposes.  Contemporary habitat restoration is largely achieved through modification of channel training structures (i.e., rock dikes) since they are a dominate feature in LMOR that structure aquatic habitats, but river hydrology is a driving component of river ecosystems.  We evaluated sauger (Sander canadensis) catch data from passive gill nets and active otter trawls between 2003 and 2011 in lower Missouri River to determine their annual size distribution, relative size class strength, and habitat use, in light of a wide range of hydrology during the study period.  Sauger-size dependent habitat use was minimally influenced by annual flow patterns.  However, young sauger production was highest in years with extended periods of high flow during the spawning season, while periods of low summer flow supported recruitment.  These results will provide insight to variation in the sauger population of lower Missouri River and guide habitat and flow management to promote population growth of this native and recreationally important fish.