Relative Bias and Precision of Age Estimates among Calcified Structures of Spotted Gar, Shortnose Gar, and Longnose Gar

Recreational angling for gars (family Lepisosteidae) has become more popular in recent years; however, the fundamental understanding of their population dynamics needed for effective management and conservation is lacking. Age data are essential for describing population dynamic rate functions, but few studies have addressed the selection of ideal calcified structures for estimating age in gars. We collected Spotted Gars Lepisosteus oculatus, Shortnose Gars L. platostomus, and Longnose Gars L. osseus from 12 Illinois water bodies to assess the relative bias and precision of age estimates derived from branchiostegal rays, pectoral fin rays, cleithra, and sagittal otoliths. Age assignments differed among these calcified structures for all three species. Branchiostegal rays underestimated the age of young fish and overestimated the age of old fish relative to all other structures. Pectoral fin rays consistently underestimated age relative to other structures and produced the lowest mean and maximum age estimates. Although there was low relative bias between readers for all structures, age assignments showed greater variability between readers for old age-classes when age estimates were derived from cleithra and otoliths. Between-reader precision was highest using pectoral fin rays, whereas cleithra and otoliths generated lower coefficients of variation and percent agreement values. These findings reveal a need to improve or modify structure processing methods to increase readability when cleithra and otoliths are used for age estimation. Given these results, future validation studies should target branchiostegal rays and pectoral fin rays to determine the most accurate calcified structure for aging gars.