Range-Wide Population Structure of Alligator Gar

The alligator gar (Atractosteus spatula) has recently received heightened attention from a conservation and management perspective.  Conservation efforts are needed across much of the range where there are declining populations.  The active management of larger populations may be needed since this fish is increasingly popular as a target of recreational fishermen, especially bow-fishing.  An understanding of alligator gar population structure is necessary to guide both restocking and management efforts. To this end, we acquired alligator gar samples from 16 sites across much of its current range and genotyped them for 8 microsatellite loci. The Texas and Louisiana populations had higher genetic variability than the rest of the range. The STRUCTURE analysis detected five genetically differentiated regions: the Rio Grande River, Choke Canyon Reservoir, eastern Texas, the Mississippi River drainage, and the northern Gulf Coast. The eastern Texas region included coastal Texas, the Brazos River, and the Trinity River, and the northern Gulf Coast region included the coastal sites from southern Louisiana to the Florida panhandle. These results should prove useful in guiding restocking efforts and developing management plans for this species.