Cooperative Fish and Wildlife Research Units Program: Nebraska
Education, Research and Technical Assistance for Managing Our Natural Resources

Accurate age estimates are critical in the development, implementation, and assessment of silver carp (Hypophthalmichthys molitrix) management plans. Lapilli otoliths are the most commonly used hard structures for silver carp age estimation, though data regarding the precision of two established preparation methods (i.e., grind-and-burn, thin-section) are lacking. To compare the two methods, we assessed within-reader, between-reader, and between-method precision for 125 silver carp collected from six rivers throughout the Lower Mississippi River Basin (Arkansas, Cache, Mississippi, St. Francis, White, and Yazoo). Additionally, we compared the effort and material costs associated with each method. Overall, the grind-and-burn method (mean age ± SE = 5.97 ± 0.18 years) resulted in younger estimated ages than the thin-section method (mean age ± SE = 6.90 ± 0.18 years), particularly in older individuals. The thin-section method (average coefficient of variation = 7.964) displayed slightly greater between-reader precision than the grind-and-burn method (average coefficient of variation = 8.072), but raw data plots revealed lower precision at older ages relative to younger ages. This discrepancy between methods may be a result of misidentification of annuli near the otolith margin as both readers reported that sectioned otoliths offered clearer views than burned and ground otoliths. Processing times and material costs were similar for the two methods and are likely not limiting when choosing an aging protocol. Our results indicate that managers may be able to use the grind-and-burn method to estimate silver carp age in younger populations where older fish are uncommon. However, the thin-section method for silver carp age estimation may lead to less biased age estimates for established populations with greater abundances of older individuals.