A Comparison of the Otolith and Scale Methods for Aging White Crappies in Oklahoma

Abstract

Scales and otoliths (sagittae) were taken from a sample of 137 white crappies (Pomoxis annularis) collected by fyke netting from Ft. Supply Reservoir, Oklahoma, in November 1982. Scales and otoliths from each fish were aged independently by three experienced scale readers, none of whom had prior experience aging otoliths. The average percent error and coefficient of variation of the scale method was approximately seven times greater than for the otolith method, indicating a greater degree of precision for the otolith method. No differences were observed in back-calculated lengths derived from measurements obtained from the right versus left otolith. No significant differences in back-calculated lengths up to age 3 for a given year class sampled in successive years were observed for white crappies aged by the otolith method. These results indicate that age and growth data generated from the otolith method would be sufficiently consistent for biologists to recognize yearly trends in growth variations. Known-age white crappies, needed to verify the accuracy of the otolith technique, were unavailable. However, scales and otoliths were taken from 31 white crappies collected from the James River arm of Table Rock Lake, Missouri, in spring 1984. The scale method for aging white crappies in Missouri is considered to be accurate by the Missouri Department of Conservation. The ages of these fish, as determined by scales read in Missouri and otoliths aged in Oklahoma, were in agreement for 30 of the 31 fish sampled. The use of the otolith method for aging white crappies in Oklahoma is recommended over the scale method. Once field personnel become efficient in extracting otoliths, processing time in the field is only slightly greater than when taking scale samples. No elaborate preparation procedures are required because ages can be obtained from whole otoliths.