The Illinois Natural History Survey is seeking a Postdoctoral Research Associate to explore and quantitatively assess existing fish length and age data to evaluate various approaches to fish stock assessment and identify/pursue data gaps to characterize reach-specific population demographics of recreational and commercially important sport fishes in Illinois and Mississippi rivers (e.g., Pool 26 of the Mississippi River, La Grange reach of the Illinois River). The results of this evaluation will guide ongoing sampling strategies to obtain an unbiased representative sample for any given sportfish species within a navigation pool and will provide information required for development and evaluation of harvest regulations. This project will be guaranteed for at least 2 years with possible exte