Accuracy and Precision of Longnose and Spotted Gar Age Estimates from Otoliths, Pectoral Fin Rays, and Branchiostegal Rays

We evaluated accuracy and precision of age estimates from Longnose Gar Lepisosteus osseus (N = 48) and Spotted Gar Lepisosteus oculatus (N = 101) sagittal otoliths, pectoral fin rays, and branchiostegal rays using oxytetracycline time-stamped fish.  Time stamps were identified in 91% of the fish otoliths, 56% of pectoral fin rays, and 0% of branchiostegal rays.  Although precision was similar among structures (percent agreement = 50-58%; CV = 6-12%), annual increment formation could only be confirmed in sagittal otoliths.  Post time-stamp annuli were correctly identified for 90.2% of the Longnose Gar (age 3-22) and 88.3% of the Spotted Gar (age 2-21).  Annual increment formation was inconsistent in pectoral fin ray sections as the majority of time stamps (> 67%) were located near the outer margin of the bone and post time-stamp annuli were not visible.  Lack of time-stamps in branchiostegal rays prevented any formal evaluation of accuracy for this structure.  Relative to age estimates from otoliths where post time-stamp annuli were correctly identified, pectoral fin rays and branchiostegal rays consistently underestimated age for both species.  While annual increment formation was validated in otoliths for both species, low precision among age readers indicates that otolith annuli can be difficult to interpret.