Largemouth bass (Micropterus salmoides) is the most sought after sportfish in New Mexico. However, population abundance of largemouth bass in Elephant Butte Reservoir remains well below the statewide target objective of 20-40 fish/h. As such, Largemouth Bass fingerlings have been stocked into the Reservoir to augment the bass population. We were tasked to retrospectively characterize the contribution of stocked versus natal (hatched in the reservoir) Largemouth Bass to assess if stocking practices were successful. We used a non-lethal collection of dorsal spines in conjunction with strontium isotopes in the spines to characterize origin of fish and learned that stocking was successful. In addition, we identified rate of water level change within the reservoir affected spawning of the bass population. We partnered with our State cooperator (New Mexico Department of Game and Fish) to conduct the research. Our results will be used to make informed management decisions on the appropriate timing of stocking fingerling Largemouth Bass. Our results will also be used by water managers to time the delivery of water throughout the middle Rio Grande Basin to increase fish habitat for spawning in Elephant Butte Reservoir.