 We developed a floodplain inundation model to estimate the availability of suitable spawning habitat for alligator gar in the Guadalupe River basin, Texas. Our analysis showed that the highest levels of suitable spawning habitat are associated with peak flows of 2057 to 3108 M3 slash S, with a total of 9,000 hectares available. Additionally, we found that alligator gar recruitment is highest when peak flows are between 5 and 3 years, with a total of 6,000 hectares available. This suggests that the Guadalupe River basin should be managed to ensure that peak flows of 5 to 3 years occur regularly to maintain healthy populations of alligator gar. This article was authored by Kimberly M. Miteson, Clinton R. Robertson, Jennifer L. Jensen and others.