Quantification of Daily Otolith Increments in Young of Year Asian Carp

Silver and bighead carp are invasive species established throughout the Mississippi River Basin. Despite the research and resources dedicated to their management, information on young-of-year Asian carp is still lacking. To help fill that gap, daily incremental growth annuli from otoliths were used to estimate age and birth dates of young-of-year Asian carp. We collected young-of-year Asian carp from the La Grange Reach of the Illinois River in August of 2014. Total length of each fish was measured, and the fish separated into 5 mm length groups (15-79 mm). Otoliths were mounted to slides, polished, photographed, and aged. Otolith microstructure was validated using known-age young-of-year Asian carp from Chinese aquaculture. Results indicate our wild caught Asian carp range from 31 to 110 days old, born between April 18 and July 6, 2014. Age frequency peaks suggest multiple or sustained spawning events in the Illinois River, and were used to relate birth dates to Illinois River stage and water temperature data. Length and age are positively correlated (p=<0.001, R2=0.32). The results from this study may help in the understanding of reproduction and recruitment, and ultimately the efficacy of management for Asian carp.