Status and Trends of Smallmouth Buffalo in the Upper Mississippi River System

Buffalo (Ictiobus sp.) are one of the most important commercially harvested species on the Upper Mississippi River system (UMRS). Despite this, little work has been done to assess buffalo populations. Using catch data from hoop nets and day electrofishing, we calculated the catch per unit effort (CPUE) for Smallmouth Buffalo (Ictiobus bubalus) in six river reaches covered by the Upper Mississippi River Restoration Program’s Long Term Resource Monitoring element (UMRR-LTRM): five pools on the Mississippi River (pools 4, 8, 13, 26 and the Open River reach) as well as the La Grange Reach on the Illinois River. Trends in CPUE for the six LTRM reaches indicate a downward trend for Smallmouth Buffalo populations since the program’s inception in 1993. In 2017, otoliths were collected from Smallmouth Buffalo from the LTRM reaches of the Mississippi River and the upper and lower Illinois River to determine the age structure of fish across multiple distinct reaches of the UMRS. A total of 664 Smallmouth Buffalo were aged and age estimates range from 0-36 years old with total annual mortality ranging from 0.06-0.097. Results from this study can be used to help inform management of the Smallmouth Buffalo commercial fishery on the UMRS.