Alligator Gar in Texas' Coastal Zone: Long-Term Trends and Environmental Influences

Annual gill-net surveys in Texas’ gulf-coast bays routinely collect Alligator Gar Atractosteus spatula.  However, little is understood about the propensity of Alligator Gar to use these habitats, and their importance to coastal river-bay stocks.  We analyzed 37 years (1975-2012) of catch data across the Texas coast to quantify spatiotemporal trends in Alligator Gar abundance and distribution and to identify environmental covariates associated with bay habitat use.  Over 28,500 Alligator Gar were collected, ranging in total length from 113 to 2,040 mm.  Catch rates varied both within and among bays; however, we detected no trends over the period of record, suggesting abundance is stable in associated populations.  Variability in catch was synchronous among bays, indicative of a common, large-scale driver of bay habitat use.  Although dissolved oxygen, turbidity, water temperature, and water depth were not related to catch, ambient salinity explained a significant portion of the variation in eight of the ten bays examined, and suggested that moderate salinities maximize bay habitat use by Alligator Gar.  Our results suggest that bay habitats support an abundance of Alligator Gar and provide important habitats in gulf-coast river systems.