Validating Aging Structures in Asian Carp from the LaGrange Reach of the Illinois River to Known-Age Asian Carp from China

Silver carp (Hypophthalmichthys molitrix) have invaded most of the Mississippi River and its tributaries. Although fish age is routinely used to inform management decisions, aging structures for bighead and silver carp have not been validated against known-age fish to ensure accuracy and utility. We used known-age fish reared in Chinese aquaculture and collected from the LaGrange Reach of the Illinois River (tracked annually from a strong 2014-year class) to validate aging structures from silver carp. We removed vertebrae, lapillus otoliths, pectoral spines, and postcleithra from each individual. Each structure was sectioned and prepared accordingly. Annuli were counted and each annulus measured from the focus using Leica S8APO Stereoscope and measuring software to determine back-calculated growth. By using both field and aquaculture reared individuals we are able to validate several silver carp aging structures and determine the most reliable structure for age, back-calculated age, and growth estimates.