Growth of fishes is infrequently measured in Arizona reservoirs, and the usefulness of different aging structures for growth analysis in this region is relatively unknown. Scales are useful aging structures in northern climates, but they may not develop readable annuli in southern states. Otoliths, cleithra, and spines are alternative aging structures and, depending on the species of fish, can be more useful; however, otolith and cleithrum samples result in mortality. We developed standard growth benchmarks and aging methods for Largemouth Bass Micropterus salmoides in Arizona reservoirs. This involved collection of aging structures (e.g., otoliths, scales) from fish caught using gill nets and electrofishing during the spring field seasons in 2020 and 2021. The aging process took place during subsequent fall and winter seasons and a comparison of the reliability of each aging structure was made. Otoliths provided the most precise data for aging Arizona Largemouth Bass. We provided AZDGF staff with age and growth benchmarks that can be used for future stock assessments in Arizona reservoirs. Field work on this project has concluded, work was included in a thesis and results are being submitted for publication.