Using Pharyngeal Teeth and Chewing Pads to Predict Juvenile Silver Carp Total Length in the La Grange Reach, Illinois River: Data

Silver carp (Hypophthalmichthys molitrix) are an invasive species in the Mississippi River Basin; understanding their vulnerability to predation as juveniles may inform control by native predators and predator stocking. Digestion of silver carp recovered from diets makes it difficult to determine the size classes most vulnerable to predation by native fishes. The objective of this study was to determine if total length of silver carp can be predicted from the size of their chewing pad, pharyngeal teeth, and pharyngeal arch, the structures most often found intact in diets. Juvenile silver carp (n=136: <180 mm) were collected using 60 hz pulsed- DC electrofishing and mini fyke nets in 2014 and 2015 from the La Grange Reach of the Illinois River. We dissected silver carp chewing pads (n= 136 fish) and pharyngeal teeth (n=127 fish) and measured chewing pad length and width, eight reproducible pharyngeal teeth landmarks, and four reproducible pharyngeal arch landmarks to the nearest 0.01 mm. Using simple linear regression we found that there is a strong predictive relationship between chewing pad, pharyngeal teeth, pharyngeal arch measurements and total length of silver carp. Chewing pad length and width were stronger predictors of silver carp length (r2= 0.94) than pharyngeal teeth (r2= 0.87), but both structures can be used to estimate silver carp total length.