Almost all reports of alligator gar in DFW are going to be other species incorrectly identified. But there are records where fish have been collected for surveys or testing that would be positively identified. And the fish records as well would have been identified by a biologist, but still on the honor of the fisherman as to where the fish was caught. Here is another record of a DFW alligator gar from TDH testing.

Description of the Trinity River 2000-2001 Sample Set
In 2000, the Seafood Safety Division (SSD) collected thirty samples along the Trinity River in the Dallas-Fort Worth metropolitan area. These sites were: (1) Clear Fork Trinity River downstream of Benbrook Lake; (2) Beach Street on the West Fork Trinity River; (3) upstream of the confluence of Elm Fork with West Fork Trinity River; (4) Trinity River downstream of Elm Fork; and (5) near the Dowdy Ferry Road Bridge. In 2001, the SSD collected nine fish from a rural area of the Trinity River near Seven Points, TX. Three of the sampling sites (Beach Street; upstream and downstream of the confluence of Elm Fork Trinity River) were within the AL-2 closure area. Three sample sites were outside the closure area. One site was upstream of the closure area: Clear Fork Trinity River in Fort Worth. Two sampling sites were downstream of the closure area: (1) Dowdy Ferry Road Bridge 5.9 km downstream of Interstate Highway 20 (I-20) in Dallas County; and (2) on the border of Navarro and Henderson Counties near the town of Seven Points, about 140 km downstream of I-20. In 2000, the SSD collected fifteen smallmouth buffalo, six common carp, two flathead catfish, one channel catfish, three longnose gar, one alligator gar and two spotted gar from Clear Fork, West Fork, and the Trinity River. In 2001, the SSD collected six blue catfish, two longnose gar, and one alligator gar from the Seven Points site.

Here's something from the lower Trinity but I bet if you get down around Kaufman you'd find some like this.........

You have not seen an alligator gar in grapevine Lake. .... they aren't in grapevine Lake

I'd say they are there in the Trinity, but exceptionally rare. Two of the places mentioned in that report are where I have seen smaller alligator gar, but only on a handful of occasions.

I know several old timers that swear up and down that Lake Grapevine used to be full of them and held some giant fish. One attributes their disappearance to bow fishing and the other to their popularity as table fare in certain communities. Too bad they are all gone.

Lake Lewisville at the mouth of the Trinity.

Years....ago...when I was a gar research nut, I talked to several old timers who said the same thing. And yes...these boys knew the difference between longnose and gator gars. I had the same experience with old timers fishing/talking 'bout the fw trinity.